diff --git a/src/core/builtins/builtins_ffmpeg_filters.ml b/src/core/builtins/builtins_ffmpeg_filters.ml
index 6c5b489365..2ecb6f2863 100644
--- a/src/core/builtins/builtins_ffmpeg_filters.ml
+++ b/src/core/builtins/builtins_ffmpeg_filters.ml
@@ -92,7 +92,9 @@ let initialized graph =
 
 let is_ready graph =
   (not graph.failed)
-  && Queue.fold (fun cur s -> cur && s#is_ready) true graph.graph_inputs
+  && Queue.fold
+       (fun cur (s : Source.source) -> cur && s#is_ready ())
+       true graph.graph_inputs
 
 let pull graph = (Clock.get (Queue.peek graph.graph_inputs)#clock)#end_tick
 
diff --git a/src/core/builtins/builtins_source.ml b/src/core/builtins/builtins_source.ml
index c16d65ec2c..c1d962ea0a 100644
--- a/src/core/builtins/builtins_source.ml
+++ b/src/core/builtins/builtins_source.ml
@@ -84,7 +84,7 @@ let _ =
        available), or currently streaming."
     [("", Lang.source_t (Lang.univ_t ()), None, None)]
     Lang.bool_t
-    (fun p -> Lang.bool (Lang.to_source (List.assoc "" p))#is_ready)
+    (fun p -> Lang.bool ((Lang.to_source (List.assoc "" p))#is_ready ()))
 
 let _ =
   Lang.add_builtin ~base:source "is_up" ~category:`System
@@ -211,7 +211,7 @@ let _ =
       Clock.unify ~pos:fo#pos fo#clock (Clock.create_known clock);
       ignore (clock#start_outputs (fun _ -> true) ());
       log#info "Start dumping source (ratio: %.02fx)" ratio;
-      while (not (Atomic.get should_stop)) && fo#is_ready do
+      while (not (Atomic.get should_stop)) && fo#is_ready () do
         let start_time = Time.time () in
         clock#end_tick;
         sleep_until (start_time |+| latency)
@@ -252,7 +252,7 @@ let _ =
       Clock.unify ~pos:o#pos o#clock (Clock.create_known clock);
       ignore (clock#start_outputs (fun _ -> true) ());
       log#info "Start dropping source (ratio: %.02fx)" ratio;
-      while (not (Atomic.get should_stop)) && o#is_ready do
+      while (not (Atomic.get should_stop)) && o#is_ready () do
         let start_time = Time.time () in
         clock#end_tick;
         sleep_until (start_time |+| latency)
diff --git a/src/core/clock.ml b/src/core/clock.ml
index f2bb578c37..bdb45219cc 100644
--- a/src/core/clock.ml
+++ b/src/core/clock.ml
@@ -208,8 +208,8 @@ module MkClock (Time : Liq_time.T) = struct
           match sync with
             | `Auto ->
                 List.exists
-                  (fun (state, s) ->
-                    state = `Active && snd s#self_sync && s#is_ready)
+                  (fun (state, (s : Source.active_source)) ->
+                    state = `Active && snd s#self_sync && s#is_ready ())
                   outputs
             | `CPU -> false
             | `None -> true
diff --git a/src/core/conversions/conversion.ml b/src/core/conversions/conversion.ml
index 4d9db863d7..29807b2bae 100644
--- a/src/core/conversions/conversion.ml
+++ b/src/core/conversions/conversion.ml
@@ -26,7 +26,7 @@ class base ?(audio = false) ?(video = false) ?(midi = false) ~converter
   (source : Source.source) =
   object (self)
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method remaining = source#remaining
     method seek = source#seek
diff --git a/src/core/conversions/swap.ml b/src/core/conversions/swap.ml
index 4e3f52c491..5d02f9c1cb 100644
--- a/src/core/conversions/swap.ml
+++ b/src/core/conversions/swap.ml
@@ -26,7 +26,7 @@ class swap ~field (source : source) =
   object
     inherit operator [source] ~name:"swap"
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method seek = source#seek
diff --git a/src/core/io/ffmpeg_filter_io.ml b/src/core/io/ffmpeg_filter_io.ml
index c9011c936b..27275ec419 100644
--- a/src/core/io/ffmpeg_filter_io.ml
+++ b/src/core/io/ffmpeg_filter_io.ml
@@ -103,7 +103,7 @@ class virtual ['a] base_output ~pass_metadata ~name ~frame_t ~field source =
     method stop = ()
     method! reset = ()
     val mutable is_up = false
-    method! is_ready = is_up && super#is_ready
+    method! is_ready ?frame () = is_up && super#is_ready ?frame ()
 
     method! wake_up l =
       is_up <- true;
@@ -247,7 +247,7 @@ class virtual ['a] input_base ~name ~pass_metadata ~self_sync_type ~self_sync
         f ()
       with Not_ready -> ()
 
-    method is_ready =
+    method private _is_ready ?frame:_ _ =
       Generator.length self#buffer >= Lazy.force Frame.size || is_ready ()
 
     method private get_frame frame =
diff --git a/src/core/io/ffmpeg_io.ml b/src/core/io/ffmpeg_io.ml
index 3df0a4a799..726400c029 100644
--- a/src/core/io/ffmpeg_io.ml
+++ b/src/core/io/ffmpeg_io.ml
@@ -75,7 +75,7 @@ class input ?(name = "input.ffmpeg") ~autostart ~self_sync ~poll_delay ~debug
     method remaining = -1
     method abort_track = Generator.add_track_mark self#buffer
     method private is_connected = Atomic.get container <> None
-    method! is_ready = super#is_ready && self#is_connected
+    method! is_ready ?frame () = super#is_ready ?frame () && self#is_connected
 
     method private get_self_sync =
       match self_sync () with Some v -> v | None -> false
diff --git a/src/core/io/gstreamer_io.ml b/src/core/io/gstreamer_io.ml
index f06b33642c..4b3c32f66b 100644
--- a/src/core/io/gstreamer_io.ml
+++ b/src/core/io/gstreamer_io.ml
@@ -487,7 +487,7 @@ class audio_video_input p (pipeline, audio_pipeline, video_pipeline) =
     (* Source is ready when ready = true and gst has some audio or some video. *)
     val mutable ready = true
 
-    method is_ready =
+    method private _is_ready =
       let pending = function
         | Some sink -> sink.pending () > 0
         | None -> false
diff --git a/src/core/io/srt_io.ml b/src/core/io/srt_io.ml
index 33b9f4f7d0..0c9c170205 100644
--- a/src/core/io/srt_io.ml
+++ b/src/core/io/srt_io.ml
@@ -681,8 +681,8 @@ class virtual input_base ~max ~clock_safe ~on_connect ~on_disconnect
     method remaining = -1
     method abort_track = Generator.add_track_mark self#buffer
 
-    method! is_ready =
-      super#is_ready && (not self#should_stop) && self#is_connected
+    method! is_ready ?frame () =
+      super#is_ready ?frame () && (not self#should_stop) && self#is_connected
 
     method self_sync = (`Dynamic, self#is_connected)
 
diff --git a/src/core/lang_source.ml b/src/core/lang_source.ml
index 6f1d40426e..9c7aa40669 100644
--- a/src/core/lang_source.ml
+++ b/src/core/lang_source.ml
@@ -66,7 +66,7 @@ let source_methods =
       "Indicate if a source is ready to stream. This does not mean that the \
        source is currently streaming, just that its resources are all properly \
        initialized.",
-      fun s -> val_fun [] (fun _ -> bool s#is_ready) );
+      fun (s : Source.source) -> val_fun [] (fun _ -> bool (s#is_ready ())) );
     ( "buffered",
       ([], fun_t [] (list_t (product_t string_t float_t))),
       "Length of buffered data.",
diff --git a/src/core/operators/accelerate.ml b/src/core/operators/accelerate.ml
index 9a7ac709f5..754ff234d1 100644
--- a/src/core/operators/accelerate.ml
+++ b/src/core/operators/accelerate.ml
@@ -47,7 +47,7 @@ class accelerate ~ratio ~randomize source_val =
       source#get_ready [(self :> source)]
 
     method! private sleep = source#leave (self :> source)
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
 
     (** Filled ticks. *)
     val mutable filled = 0
@@ -75,13 +75,13 @@ class accelerate ~ratio ~randomize source_val =
       let pos = ref 1 in
       (* Drop frames if we are late. *)
       (* TODO: we could also duplicate if we are in advance. *)
-      while !pos > 0 && self#must_drop && source#is_ready do
+      while !pos > 0 && self#must_drop && source#is_ready ~frame () do
         Frame.clear null;
         self#child_on_output (fun () -> source#get null);
         pos := Frame.position null;
         skipped <- skipped + !pos
       done;
-      if source#is_ready then (
+      if source#is_ready ~frame () then (
         let before = Frame.position frame in
         if !pos > 0 then self#child_on_output (fun () -> source#get frame);
         let after = Frame.position frame in
diff --git a/src/core/operators/add.ml b/src/core/operators/add.ml
index 86e549682b..6a293fba06 100644
--- a/src/core/operators/add.ml
+++ b/src/core/operators/add.ml
@@ -51,10 +51,13 @@ class virtual base ~name tracks =
       List.fold_left f (-1)
         (List.map
            (fun s -> s#remaining)
-           (List.filter (fun s -> s#is_ready) sources))
+           (List.filter (fun (s : Source.source) -> s#is_ready ()) sources))
 
     method abort_track = List.iter (fun s -> s#abort_track) sources
-    method is_ready = List.exists (fun s -> s#is_ready) sources
+
+    method private _is_ready ?frame () =
+      List.exists (fun s -> s#is_ready ?frame ()) sources
+
     method seek n = match sources with [s] -> s#seek n | _ -> 0
 
     method seek_source =
@@ -89,7 +92,7 @@ class virtual base ~name tracks =
       match
         List.fold_left
           (fun cur { fields; source } ->
-            if not source#is_ready then cur
+            if not (source#is_ready ~frame:buf ()) then cur
             else
               List.fold_left
                 (fun cur { position; _ } ->
@@ -136,8 +139,8 @@ class audio_add ~renorm ~power ~field tracks =
                 (0., []) fields
             in
             ( total_weight +. source_weight,
-              if source#is_ready then { source; fields } :: tracks else tracks
-            ))
+              if source#is_ready ~frame:buf () then { source; fields } :: tracks
+              else tracks ))
           (0., []) tracks
       in
       let total_weight = if power then sqrt total_weight else total_weight in
@@ -171,7 +174,8 @@ class video_add ~field ~add tracks =
       let tracks =
         List.fold_left
           (fun tracks track ->
-            if track.source#is_ready then track :: tracks else tracks)
+            if track.source#is_ready ~frame:buf () then track :: tracks
+            else tracks)
           [] tracks
       in
       let offset = Frame.position buf in
diff --git a/src/core/operators/amplify.ml b/src/core/operators/amplify.ml
index 3d75e77464..32cbc30db1 100644
--- a/src/core/operators/amplify.ml
+++ b/src/core/operators/amplify.ml
@@ -28,7 +28,7 @@ class amplify ~field (source : source) override_field coeff =
     inherit operator ~name:"track.audio.amplify" [source]
     val mutable override = None
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method seek = source#seek
diff --git a/src/core/operators/available.ml b/src/core/operators/available.ml
index 18986766dd..263096f507 100644
--- a/src/core/operators/available.ml
+++ b/src/core/operators/available.ml
@@ -33,9 +33,9 @@ class available ~track_sensitive ~override p (source : source) =
     method self_sync = source#self_sync
     val mutable ready = p ()
 
-    method is_ready =
+    method private _is_ready ?frame () =
       if not (track_sensitive () && ready) then ready <- p ();
-      ready && (override || source#is_ready)
+      ready && (override || source#is_ready ?frame ())
 
     method private get_frame buf =
       source#get buf;
diff --git a/src/core/operators/biquad_filter.ml b/src/core/operators/biquad_filter.ml
index 67d38f2ca5..6b0da64e97 100644
--- a/src/core/operators/biquad_filter.ml
+++ b/src/core/operators/biquad_filter.ml
@@ -123,7 +123,7 @@ class biquad (source : source) filter_type freq q gain =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
 
     method! wake_up a =
diff --git a/src/core/operators/chord.ml b/src/core/operators/chord.ml
index c1ee728047..96484886e5 100644
--- a/src/core/operators/chord.ml
+++ b/src/core/operators/chord.ml
@@ -48,7 +48,7 @@ class chord metadata_name (source : source) =
     inherit operator ~name:"chord" [source]
     method stype = source#stype
     method remaining = source#remaining
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/clip.ml b/src/core/operators/clip.ml
index 94771261d2..7300c73bee 100644
--- a/src/core/operators/clip.ml
+++ b/src/core/operators/clip.ml
@@ -30,7 +30,7 @@ class clip ~field (source : source) =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
 
diff --git a/src/core/operators/comb.ml b/src/core/operators/comb.ml
index 9ae4e0a58f..fa17a50a38 100644
--- a/src/core/operators/comb.ml
+++ b/src/core/operators/comb.ml
@@ -34,7 +34,7 @@ class comb ~field (source : source) delay feedback =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     val mutable past = Audio.make 0 0 0.
 
diff --git a/src/core/operators/compand.ml b/src/core/operators/compand.ml
index 18b14dd8bb..ac603ba18f 100644
--- a/src/core/operators/compand.ml
+++ b/src/core/operators/compand.ml
@@ -30,7 +30,7 @@ class compand ~field (source : source) mu =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
 
     method private get_frame buf =
diff --git a/src/core/operators/compress.ml b/src/core/operators/compress.ml
index 2f892e50d7..a0f5705a9b 100644
--- a/src/core/operators/compress.ml
+++ b/src/core/operators/compress.ml
@@ -40,7 +40,7 @@ class compress ~attack ~release ~threshold ~ratio ~knee ~track_sensitive
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
 
     (* Current gain in dB. *)
diff --git a/src/core/operators/compress_exp.ml b/src/core/operators/compress_exp.ml
index 925181392c..77d6e66928 100644
--- a/src/core/operators/compress_exp.ml
+++ b/src/core/operators/compress_exp.ml
@@ -27,7 +27,7 @@ class compress ~field (source : source) mu =
     inherit operator ~name:"compress" [source]
     method stype = source#stype
     method remaining = source#remaining
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/cross.ml b/src/core/operators/cross.ml
index 83d08b8cc5..2313a75dd1 100644
--- a/src/core/operators/cross.ml
+++ b/src/core/operators/cross.ml
@@ -205,16 +205,17 @@ class cross val_source ~duration_getter ~override_duration ~persist_override
         | `Limit ->
             (* The track finished.
              * We compute rms_after and launch the transition. *)
-            if source#is_ready then self#analyze_after;
+            if source#is_ready ~frame () then self#analyze_after;
             self#create_transition;
 
             (* Check if the new source is ready *)
-            if (Option.get transition_source)#is_ready then self#get_frame frame
+            if (Option.get transition_source)#is_ready ~frame () then
+              self#get_frame frame
             else
               (* If not, finish this track, which requires our callers
                * to wait that we become ready again. *)
               Frame.add_break frame (Frame.position frame)
-        | `After when (Option.get transition_source)#is_ready ->
+        | `After when (Option.get transition_source)#is_ready ~frame () ->
             self#child_get (Option.get transition_source) frame;
 
             if Generator.length pending_after = 0 && Frame.is_partial frame then (
@@ -225,7 +226,7 @@ class cross val_source ~duration_getter ~override_duration ~persist_override
                * using it. Each call to [get_frame] must add exactly one break so
                * call it again and then remove the intermediate break that was just
                * added. *)
-              if source#is_ready then (
+              if source#is_ready ~frame () then (
                 self#get_frame frame;
                 Frame.set_breaks frame
                   (match List.rev (Frame.breaks frame) with
@@ -294,8 +295,10 @@ class cross val_source ~duration_getter ~override_duration ~persist_override
           rmsi_after <- rmsi_after + len);
         self#save_last_metadata `After buf_frame;
         self#update_cross_length buf_frame start;
-        if AFrame.is_partial buf_frame && not source#is_ready then
-          Generator.add_track_mark gen_after
+        if
+          AFrame.is_partial buf_frame
+          && not (source#is_ready ~frame:buf_frame ())
+        then Generator.add_track_mark gen_after
         else (
           if not (Frame.is_partial buf_frame) then Frame.clear buf_frame;
           if after_len < before_len then f ())
@@ -396,14 +399,16 @@ class cross val_source ~duration_getter ~override_duration ~persist_override
         | `After -> Option.get transition_source
         | _ -> (self :> Source.source)
 
-    method is_ready =
+    method private _is_ready ?frame () =
       match status with
-        | `Idle | `Before -> source#is_ready
+        | `Idle | `Before -> source#is_ready ?frame ()
         | `Limit -> true
-        | `After -> (Option.get transition_source)#is_ready || source#is_ready
+        | `After ->
+            (Option.get transition_source)#is_ready ?frame ()
+            || source#is_ready ?frame ()
 
     method abort_track =
-      if status = `After && (Option.get transition_source)#is_ready then
+      if status = `After && (Option.get transition_source)#is_ready () then
         (Option.get transition_source)#abort_track
       else source#abort_track
   end
diff --git a/src/core/operators/cuepoint.ml b/src/core/operators/cuepoint.ml
index 01241d3ce0..3b17080ba9 100644
--- a/src/core/operators/cuepoint.ml
+++ b/src/core/operators/cuepoint.ml
@@ -43,7 +43,7 @@ class cue_cut ~m_cue_in ~m_cue_out ~on_cue_in ~on_cue_out source_val =
     inherit! Child_support.base ~check_self_sync:true [source_val]
     val mutable track_state : state = `Idle
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
     method seek = source#seek
diff --git a/src/core/operators/defer.ml b/src/core/operators/defer.ml
index 54d910ad0a..7a4b495a12 100644
--- a/src/core/operators/defer.ml
+++ b/src/core/operators/defer.ml
@@ -97,7 +97,7 @@ class defer ~delay ~overhead ~field source =
       let tmp_frame = self#tmp_frame in
       Frame.clear tmp_frame;
 
-      while Frame.is_partial tmp_frame && source#is_ready do
+      while Frame.is_partial tmp_frame && source#is_ready ~frame:tmp_frame () do
         source#get tmp_frame
       done;
       let gen_len = Frame.position tmp_frame in
@@ -138,7 +138,7 @@ class defer ~delay ~overhead ~field source =
     method private queue_output =
       let clock = Source.Clock_variables.get self#clock in
       clock#on_output (fun () ->
-          if source#is_ready then self#buffer_data;
+          if source#is_ready () then self#buffer_data;
           if should_queue then
             clock#on_before_output (fun () -> self#queue_output))
 
@@ -148,7 +148,9 @@ class defer ~delay ~overhead ~field source =
           self#queue_output);
       self#on_sleep (fun () -> should_queue <- false)
 
-    method is_ready = (not deferred) && Generator.length self#generator > 0
+    method private _is_ready ?frame:_ _ =
+      (not deferred) && Generator.length self#generator > 0
+
     method private get_frame buf = Generator.fill self#generator buf
   end
 
diff --git a/src/core/operators/delay.ml b/src/core/operators/delay.ml
index f0dfe529e3..bf4914695a 100644
--- a/src/core/operators/delay.ml
+++ b/src/core/operators/delay.ml
@@ -46,8 +46,8 @@ class delay ~initial (source : source) delay =
       in_track <- false;
       last <- Unix.time ()
 
-    method is_ready =
-      let is_ready = source#is_ready in
+    method private _is_ready ?frame () =
+      let is_ready = source#is_ready ?frame () in
       if in_track && not is_ready then self#end_track;
       self#delay_ok && is_ready
 
diff --git a/src/core/operators/delay_line.ml b/src/core/operators/delay_line.ml
index 50849302be..377243b6eb 100644
--- a/src/core/operators/delay_line.ml
+++ b/src/core/operators/delay_line.ml
@@ -29,7 +29,7 @@ class delay (source : source) duration =
     inherit operator ~name:"amplify" [source] as super
     val mutable override = None
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method seek = source#seek
diff --git a/src/core/operators/dtmf.ml b/src/core/operators/dtmf.ml
index aecc1fdd0a..957c0be740 100644
--- a/src/core/operators/dtmf.ml
+++ b/src/core/operators/dtmf.ml
@@ -159,7 +159,7 @@ class dtmf ~duration ~bands ~threshold ~smoothing ~debug callback
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
 
@@ -297,7 +297,7 @@ class detect ~duration ~bands ~threshold ~smoothing ~debug ~frequencies callback
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
     val bands = Bands.make ~size:nbands ~samplerate frequencies
diff --git a/src/core/operators/dyn_op.ml b/src/core/operators/dyn_op.ml
index ca874d483a..ad78490e4e 100644
--- a/src/core/operators/dyn_op.ml
+++ b/src/core/operators/dyn_op.ml
@@ -83,10 +83,10 @@ class dyn ~init ~track_sensitive ~infallible ~resurection_time f =
         f;
       self#unregister_source ~already_locked:false
 
-    method is_ready =
+    method private _is_ready ?frame () =
       if (not track_sensitive) || source = None then self#select;
       match source with
-        | Some s when s#is_ready -> true
+        | Some s when s#is_ready ?frame () -> true
         | _ ->
             if
               track_sensitive && resurection_time <> None
diff --git a/src/core/operators/echo.ml b/src/core/operators/echo.ml
index 17586e9e5a..9b1ea476ad 100644
--- a/src/core/operators/echo.ml
+++ b/src/core/operators/echo.ml
@@ -31,7 +31,7 @@ class echo (source : source) delay feedback ping_pong =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     val mutable effect = None
 
diff --git a/src/core/operators/filter.ml b/src/core/operators/filter.ml
index aa9f26b87b..19c3e194f6 100644
--- a/src/core/operators/filter.ml
+++ b/src/core/operators/filter.ml
@@ -32,7 +32,7 @@ class filter (source : source) freq q wet mode =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
     val mutable low = [||]
diff --git a/src/core/operators/filter_rc.ml b/src/core/operators/filter_rc.ml
index fa96cc7c50..1c882dc411 100644
--- a/src/core/operators/filter_rc.ml
+++ b/src/core/operators/filter_rc.ml
@@ -34,7 +34,7 @@ class filter (source : source) freq wet mode =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     val mutable prev = [||]
     val mutable prev_in = [||]
diff --git a/src/core/operators/fir_filter.ml b/src/core/operators/fir_filter.ml
index 0986d0e521..a30bb7cc83 100644
--- a/src/core/operators/fir_filter.ml
+++ b/src/core/operators/fir_filter.ml
@@ -123,7 +123,7 @@ class fir (source : source) freq beta numcoeffs =
     (* Digital filter based on mkfilter/mkshape/gencode by A.J. Fisher *)
     method stype = source#stype
     method remaining = source#remaining
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method seek = source#seek
     method seek_source = source
     method abort_track = source#abort_track
diff --git a/src/core/operators/flanger.ml b/src/core/operators/flanger.ml
index 5c86ecf6c4..4b0005820f 100644
--- a/src/core/operators/flanger.ml
+++ b/src/core/operators/flanger.ml
@@ -34,7 +34,7 @@ class flanger (source : source) delay freq feedback phase =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     val mutable past = Audio.make 0 0 0.
 
diff --git a/src/core/operators/frei0r_op.ml b/src/core/operators/frei0r_op.ml
index b5c4966513..c0a5413ec7 100644
--- a/src/core/operators/frei0r_op.ml
+++ b/src/core/operators/frei0r_op.ml
@@ -51,7 +51,7 @@ class frei0r_filter ~name bgra instance params (source : source) =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = (self :> Source.source)
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method self_sync = source#self_sync
     method abort_track = source#abort_track
     val mutable t = 0.
@@ -95,7 +95,8 @@ class frei0r_mixer ~name bgra instance params (source : source) source2 =
         | -1, x | x, -1 -> x
         | x, y -> min x y
 
-    method is_ready = source#is_ready && source2#is_ready
+    method private _is_ready ?frame () =
+      source#is_ready ?frame () && source2#is_ready ?frame ()
 
     method self_sync =
       match (source#self_sync, source2#self_sync) with
@@ -164,7 +165,7 @@ class frei0r_source ~name bgra instance params =
     inherit Source.no_seek
     method seek_source = (self :> Source.source)
     method stype = `Infallible
-    method is_ready = true
+    method private _is_ready ?frame:_ _ = true
     method self_sync = (`Static, false)
     val mutable must_fail = false
     method abort_track = must_fail <- true
diff --git a/src/core/operators/gate.ml b/src/core/operators/gate.ml
index 32db48e390..639646dda2 100644
--- a/src/core/operators/gate.ml
+++ b/src/core/operators/gate.ml
@@ -30,7 +30,7 @@ class gate ~threshold ~attack ~release ~hold ~range ~window (source : source) =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
 
diff --git a/src/core/operators/iir_filter.ml b/src/core/operators/iir_filter.ml
index 905d250c3f..e5dd3ac976 100644
--- a/src/core/operators/iir_filter.ml
+++ b/src/core/operators/iir_filter.ml
@@ -416,7 +416,7 @@ class iir (source : source) filter_family filter_type order freq1 freq2 qfactor
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     val mutable v_offs = 0
 
diff --git a/src/core/operators/insert_metadata.ml b/src/core/operators/insert_metadata.ml
index 5eb3b70de3..40c07e29b7 100644
--- a/src/core/operators/insert_metadata.ml
+++ b/src/core/operators/insert_metadata.ml
@@ -29,7 +29,7 @@ class insert_metadata source =
   object (self)
     inherit operator ~name:"insert_metadata" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
@@ -122,7 +122,7 @@ class replay meta src =
     inherit operator ~name:"replay_metadata" [src]
     val mutable first = true
     method stype = src#stype
-    method is_ready = src#is_ready
+    method private _is_ready = src#is_ready
     method abort_track = src#abort_track
     method remaining = src#remaining
     method self_sync = src#self_sync
diff --git a/src/core/operators/ladspa_op.ml b/src/core/operators/ladspa_op.ml
index c2c159b2f7..9758252839 100644
--- a/src/core/operators/ladspa_op.ml
+++ b/src/core/operators/ladspa_op.ml
@@ -64,7 +64,7 @@ class virtual base source =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = (self :> Source.source)
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method self_sync = source#self_sync
     method abort_track = source#abort_track
   end
@@ -75,7 +75,7 @@ class virtual base_nosource =
     inherit Source.no_seek
     method seek_source = (self :> Source.source)
     method stype = `Infallible
-    method is_ready = true
+    method private _is_ready ?frame:_ _ = true
     method self_sync = (`Static, false)
     val mutable must_fail = false
     method abort_track = must_fail <- true
diff --git a/src/core/operators/lilv_op.ml b/src/core/operators/lilv_op.ml
index 2d27feee60..4a5e588e21 100644
--- a/src/core/operators/lilv_op.ml
+++ b/src/core/operators/lilv_op.ml
@@ -40,7 +40,7 @@ class virtual base source =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method self_sync = source#self_sync
     method abort_track = source#abort_track
   end
@@ -51,7 +51,7 @@ class virtual base_nosource =
     inherit Source.no_seek
     method seek_source = (self :> Source.source)
     method stype = `Infallible
-    method is_ready = true
+    method private _is_ready ?frame:_ _ = true
     val mutable must_fail = false
     method abort_track = must_fail <- true
     method remaining = -1
diff --git a/src/core/operators/lufs.ml b/src/core/operators/lufs.ml
index 67f4b7b183..c9d4467d53 100644
--- a/src/core/operators/lufs.ml
+++ b/src/core/operators/lufs.ml
@@ -107,7 +107,7 @@ class lufs window source =
   object (self)
     inherit operator [source] ~name:"lufs" as super
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/map_metadata.ml b/src/core/operators/map_metadata.ml
index 8cbc6e3cea..09400fb259 100644
--- a/src/core/operators/map_metadata.ml
+++ b/src/core/operators/map_metadata.ml
@@ -27,7 +27,7 @@ class map_metadata source rewrite_f insert_missing update strip =
     inherit operator ~name:"metadata.map" [source]
     initializer Typing.(self#frame_type <: Lang.unit_t)
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method seek n = source#seek n
diff --git a/src/core/operators/map_op.ml b/src/core/operators/map_op.ml
index dde3499eb3..e7d207c9f5 100644
--- a/src/core/operators/map_op.ml
+++ b/src/core/operators/map_op.ml
@@ -30,7 +30,7 @@ class map ~field source f =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
 
     method private get_frame buf =
diff --git a/src/core/operators/max_duration.ml b/src/core/operators/max_duration.ml
index 858097bef5..353969c33c 100644
--- a/src/core/operators/max_duration.ml
+++ b/src/core/operators/max_duration.ml
@@ -38,7 +38,7 @@ class max_duration ~override_meta ~duration source =
 
     method! private sleep = s#leave (self :> Source.operator)
     method stype = `Fallible
-    method is_ready = remaining > 0 && s#is_ready
+    method private _is_ready ?frame () = remaining > 0 && s#is_ready ?frame ()
     method abort_track = s#abort_track
 
     method remaining =
diff --git a/src/core/operators/midi_routing.ml b/src/core/operators/midi_routing.ml
index 6c582b920e..5748203abd 100644
--- a/src/core/operators/midi_routing.ml
+++ b/src/core/operators/midi_routing.ml
@@ -31,7 +31,7 @@ class virtual base ~name (source : source) =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
   end
 
diff --git a/src/core/operators/ms_stereo.ml b/src/core/operators/ms_stereo.ml
index 386fc1c887..76c683547d 100644
--- a/src/core/operators/ms_stereo.ml
+++ b/src/core/operators/ms_stereo.ml
@@ -28,7 +28,7 @@ class msstereo ~field (source : source) mode width =
   object
     inherit operator ~name:"stereo.ms.encode" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
@@ -91,7 +91,7 @@ class spatializer ~field ~width (source : source) =
   object
     inherit operator ~name:"stereo.width" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/muxer.ml b/src/core/operators/muxer.ml
index c3e8a0976c..6960f42a90 100644
--- a/src/core/operators/muxer.ml
+++ b/src/core/operators/muxer.ml
@@ -57,8 +57,12 @@ class muxer tracks =
       (Lazy.force self_sync_type, List.exists (fun s -> snd s#self_sync) sources)
 
     method abort_track = List.iter (fun s -> s#abort_track) sources
-    method private sources_ready = List.for_all (fun s -> s#is_ready) sources
-    method is_ready = Generator.length self#buffer > 0 || self#sources_ready
+
+    method private sources_ready ?frame () =
+      List.for_all (fun s -> s#is_ready ?frame ()) sources
+
+    method private _is_ready ?frame () =
+      Generator.length self#buffer > 0 || self#sources_ready ?frame ()
 
     method seek len =
       let gen_len = min (Generator.length self#buffer) len in
@@ -90,7 +94,7 @@ class muxer tracks =
           List.fold_left
             (fun r s -> if r = -1 then s#remaining else min r s#remaining)
             (-1)
-            (List.filter (fun s -> s#is_ready) sources) )
+            (List.filter (fun (s : Source.source) -> s#is_ready ()) sources) )
       with
         | -1, r -> r
         | r, _ -> r
@@ -118,7 +122,7 @@ class muxer tracks =
     method private feed_fields ~filled { fields; source } =
       let tmp = self#track_frame source in
       let start = Frame.position tmp in
-      if Frame.is_partial tmp && source#is_ready then (
+      if Frame.is_partial tmp && source#is_ready ~frame:tmp () then (
         source#get tmp;
         let stop = Frame.position tmp in
         List.iter (self#feed_track ~tmp ~filled ~start ~stop) fields)
@@ -131,7 +135,7 @@ class muxer tracks =
     method private feed ~force buf =
       let filled = Frame.position buf in
       if
-        self#sources_ready
+        self#sources_ready ()
         && (force
            || Generator.remaining self#buffer = -1
               && filled + Generator.length self#buffer < Lazy.force Frame.size)
diff --git a/src/core/operators/noblank.ml b/src/core/operators/noblank.ml
index a4e6048f91..cd06c6cd2d 100644
--- a/src/core/operators/noblank.ml
+++ b/src/core/operators/noblank.ml
@@ -87,7 +87,7 @@ class detect ~start_blank ~max_blank ~min_noise ~threshold ~track_sensitive
     inherit operator ~name:"blank.detect" [source]
     inherit base ~track_sensitive ~start_blank ~max_blank ~min_noise ~threshold
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method remaining = source#remaining
     method seek = source#seek
@@ -117,7 +117,10 @@ class strip ~start_blank ~max_blank ~min_noise ~threshold ~track_sensitive
     inherit active_operator ~name:"blank.strip" [source]
     inherit base ~track_sensitive ~start_blank ~max_blank ~min_noise ~threshold
     method stype = `Fallible
-    method is_ready = (not self#is_blank) && source#is_ready
+
+    method private _is_ready ?frame () =
+      (not self#is_blank) && source#is_ready ?frame ()
+
     method remaining = if self#is_blank then 0 else source#remaining
     method seek n = if self#is_blank then 0 else source#seek n
 
@@ -145,8 +148,11 @@ class strip ~start_blank ~max_blank ~min_noise ~threshold ~track_sensitive
        * the track ends, the beginning of the next track won't be lost. (Because
        * of granularity issues, the change of #is_ready only takes effect at the
        * end of the clock cycle). *)
-      if source#is_ready && self#is_blank && AFrame.is_partial self#memo then
-        self#get_frame self#memo
+      if
+        source#is_ready ~frame:self#memo ()
+        && self#is_blank
+        && AFrame.is_partial self#memo
+      then self#get_frame self#memo
 
     method reset = ()
   end
@@ -166,7 +172,7 @@ class eat ~track_sensitive ~at_beginning ~start_blank ~max_blank ~min_noise
     val mutable stripping = false
     val mutable beginning = true
     method stype = `Fallible
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/normalize.ml b/src/core/operators/normalize.ml
index d484007e74..53f0c9b036 100644
--- a/src/core/operators/normalize.ml
+++ b/src/core/operators/normalize.ml
@@ -66,7 +66,7 @@ class normalize ~track_sensitive (source : source) (* RMS target. *) rmst
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
 
     method private get_frame buf =
diff --git a/src/core/operators/on_end.ml b/src/core/operators/on_end.ml
index 747d1a5117..3ebc90b6d1 100644
--- a/src/core/operators/on_end.ml
+++ b/src/core/operators/on_end.ml
@@ -26,7 +26,7 @@ class on_end ~delay f s =
     inherit Latest_metadata.source
     val mutable executed = false
     method stype = s#stype
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     method remaining = s#remaining
     method abort_track = s#abort_track
     method seek n = s#seek n
diff --git a/src/core/operators/on_frame.ml b/src/core/operators/on_frame.ml
index 6c00e57b63..0a0b21507e 100644
--- a/src/core/operators/on_frame.ml
+++ b/src/core/operators/on_frame.ml
@@ -24,7 +24,7 @@ class on_frame f s =
   object
     inherit Source.operator ~name:"on_frame" [s]
     method stype = s#stype
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     method abort_track = s#abort_track
     method remaining = s#remaining
     method seek n = s#seek n
@@ -60,7 +60,7 @@ class frame_op ~name f default s =
   object
     inherit Source.operator ~name [s]
     method stype = s#stype
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     method abort_track = s#abort_track
     method remaining = s#remaining
     method seek n = s#seek n
diff --git a/src/core/operators/on_metadata.ml b/src/core/operators/on_metadata.ml
index 18751297d8..4d68eb7362 100644
--- a/src/core/operators/on_metadata.ml
+++ b/src/core/operators/on_metadata.ml
@@ -24,7 +24,7 @@ class on_metadata f s =
   object (self)
     inherit Source.operator ~name:"on_metadata" [s]
     method stype = s#stype
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     method abort_track = s#abort_track
     method remaining = s#remaining
     method seek n = s#seek n
diff --git a/src/core/operators/on_offset.ml b/src/core/operators/on_offset.ml
index 782ad120c2..bf37b85e0d 100644
--- a/src/core/operators/on_offset.ml
+++ b/src/core/operators/on_offset.ml
@@ -33,7 +33,7 @@ class on_offset ~force ~offset f s =
     inherit Source.operator ~name:"on_offset" [s]
     inherit Latest_metadata.source
     method stype = s#stype
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     method remaining = s#remaining
     method abort_track = s#abort_track
     method seek n = s#seek n
diff --git a/src/core/operators/on_track.ml b/src/core/operators/on_track.ml
index f5b34c71f9..7986ac44d0 100644
--- a/src/core/operators/on_track.ml
+++ b/src/core/operators/on_track.ml
@@ -24,7 +24,7 @@ class on_track f s =
   object
     inherit Source.operator ~name:"on_track" [s]
     method stype = s#stype
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     method abort_track = s#abort_track
     method remaining = s#remaining
     method seek n = s#seek n
diff --git a/src/core/operators/pan.ml b/src/core/operators/pan.ml
index 86256ca2d9..272fe3fb05 100644
--- a/src/core/operators/pan.ml
+++ b/src/core/operators/pan.ml
@@ -27,7 +27,7 @@ class pan ~field (source : source) phi phi_0 =
   object
     inherit operator ~name:"pan" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/pipe.ml b/src/core/operators/pipe.ml
index bde8331ed8..3dba45a8fe 100644
--- a/src/core/operators/pipe.ml
+++ b/src/core/operators/pipe.ml
@@ -153,7 +153,7 @@ class pipe ~replay_delay ~data_len ~process ~bufferize ~max ~restart
             t
 
     method private get_to_write =
-      if source#is_ready then (
+      if source#is_ready ~frame:self#tmp () then (
         Frame.clear self#tmp;
         self#child_on_output (fun () -> source#get self#tmp);
         let buf = AFrame.pcm self#tmp in
diff --git a/src/core/operators/pitch.ml b/src/core/operators/pitch.ml
index 42a7553dbc..b16b03973d 100644
--- a/src/core/operators/pitch.ml
+++ b/src/core/operators/pitch.ml
@@ -81,7 +81,7 @@ class pitch every length freq_min freq_max (source : source) =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
 
diff --git a/src/core/operators/replaygain_op.ml b/src/core/operators/replaygain_op.ml
index 15af82247f..5875192cd4 100644
--- a/src/core/operators/replaygain_op.ml
+++ b/src/core/operators/replaygain_op.ml
@@ -28,7 +28,7 @@ class replaygain (source : source) =
     inherit operator ~name:"source.replaygain.compute" [source]
     val mutable override = None
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method seek = source#seek
diff --git a/src/core/operators/resample.ml b/src/core/operators/resample.ml
index e3bee51146..ed058a56f4 100644
--- a/src/core/operators/resample.ml
+++ b/src/core/operators/resample.ml
@@ -51,7 +51,7 @@ class resample ~field ~ratio source =
       else int_of_float (float (rem + Generator.length self#buffer) *. ratio ())
 
     method abort_track = source#abort_track
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     val mutable converter = None
 
     method! wake_up a =
@@ -84,7 +84,8 @@ class resample ~field ~ratio source =
     method private get_frame frame =
       consumer#set_output_enabled true;
       while
-        Generator.length self#buffer < Lazy.force Frame.size && source#is_ready
+        Generator.length self#buffer < Lazy.force Frame.size
+        && source#is_ready ~frame:self#buffer ()
       do
         self#child_tick
       done;
diff --git a/src/core/operators/rms_smooth.ml b/src/core/operators/rms_smooth.ml
index 039459ba78..e10343f329 100644
--- a/src/core/operators/rms_smooth.ml
+++ b/src/core/operators/rms_smooth.ml
@@ -27,7 +27,7 @@ class rms ~tau source =
   object (self)
     inherit operator [source] ~name:"rms" as super
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/operators/sequence.ml b/src/core/operators/sequence.ml
index bf39e3d443..fcd756ca9c 100644
--- a/src/core/operators/sequence.ml
+++ b/src/core/operators/sequence.ml
@@ -59,8 +59,8 @@ class sequence ?(merge = false) sources =
     * inserted an end of track automatically instead of calling #get_frame. *)
     val mutable head_ready = false
 
-    method is_ready =
-      head_ready || List.exists (fun s -> s#is_ready) seq_sources
+    method private _is_ready ?frame () =
+      head_ready || List.exists (fun s -> s#is_ready ?frame ()) seq_sources
 
     method remaining =
       if merge then (
@@ -88,7 +88,7 @@ class sequence ?(merge = false) sources =
           head_ready <- false;
           if List.length seq_sources > 1 then (
             seq_sources <- List.tl seq_sources;
-            if merge && self#is_ready then (
+            if merge && self#is_ready ~frame:buf () then (
               let pos = Frame.position buf in
               self#get_frame buf;
               Frame.set_breaks buf
@@ -96,10 +96,11 @@ class sequence ?(merge = false) sources =
       else (
         match seq_sources with
           | a :: (_ :: _ as tl) ->
-              if a#is_ready then head_ready <- true else seq_sources <- tl;
+              if a#is_ready ~frame:buf () then head_ready <- true
+              else seq_sources <- tl;
               self#get_frame buf
           | [a] ->
-              assert a#is_ready;
+              assert (a#is_ready ~frame:buf ());
 
               (* Our #is_ready ensures that. *)
               head_ready <- true;
@@ -111,7 +112,7 @@ class merge_tracks source =
   object (self)
     inherit operator ~name:"sequence" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method remaining = -1
     method self_sync = source#self_sync
@@ -120,7 +121,7 @@ class merge_tracks source =
 
     method private get_frame buf =
       source#get buf;
-      if Frame.is_partial buf && source#is_ready then (
+      if Frame.is_partial buf && source#is_ready ~frame:buf () then (
         self#log#info "End of track: merging.";
         self#get_frame buf;
         Frame.set_breaks buf
diff --git a/src/core/operators/soundtouch_op.ml b/src/core/operators/soundtouch_op.ml
index 98d34c89c2..f3b3bb7206 100644
--- a/src/core/operators/soundtouch_op.ml
+++ b/src/core/operators/soundtouch_op.ml
@@ -41,7 +41,7 @@ class soundtouch source_val rate tempo pitch =
     val mutable st = None
     method stype = source#stype
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method seek = source#seek
     method seek_source = source
     method remaining = -1
@@ -77,7 +77,8 @@ class soundtouch source_val rate tempo pitch =
     method private get_frame buf =
       consumer#set_output_enabled true;
       while
-        Generator.length self#buffer < Lazy.force Frame.size && source#is_ready
+        Generator.length self#buffer < Lazy.force Frame.size
+        && source#is_ready ~frame:self#buffer ()
       do
         self#child_tick
       done;
diff --git a/src/core/operators/st_bpm.ml b/src/core/operators/st_bpm.ml
index 5478094c7c..e96f4eb28b 100644
--- a/src/core/operators/st_bpm.ml
+++ b/src/core/operators/st_bpm.ml
@@ -26,7 +26,7 @@ class bpm (source : source) =
   object (self)
     inherit operator ~name:"bpm" [source] as super
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method self_sync = source#self_sync
     method remaining = source#remaining
     method seek = source#seek
diff --git a/src/core/operators/stereotool_op.ml b/src/core/operators/stereotool_op.ml
index b5c57b74a8..e3beb88dfc 100644
--- a/src/core/operators/stereotool_op.ml
+++ b/src/core/operators/stereotool_op.ml
@@ -76,7 +76,7 @@ class stereotool ~field ~handler source =
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method self_sync = source#self_sync
 
diff --git a/src/core/operators/still_frame.ml b/src/core/operators/still_frame.ml
index 2c59225e72..657afd6f4b 100644
--- a/src/core/operators/still_frame.ml
+++ b/src/core/operators/still_frame.ml
@@ -34,7 +34,7 @@ class still_frame ~name (source : source) =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     val mutable fname = None
 
diff --git a/src/core/operators/switch.ml b/src/core/operators/switch.ml
index 42dd84e256..99b998c03a 100644
--- a/src/core/operators/switch.ml
+++ b/src/core/operators/switch.ml
@@ -114,7 +114,8 @@ class virtual switch ~name ~override_meta ~transition_length
       if self#is_selected_generated then
         (Option.get selected).effective_source#leave (self :> source)
 
-    method is_ready = need_eot || selected <> None || self#cached_select <> None
+    method private _is_ready ?frame:_ _ =
+      need_eot || selected <> None || self#cached_select <> None
 
     (* This one is tricky. We do not want to call #cached_select as
        this requires some run-time info from underlying sources
@@ -317,7 +318,7 @@ class lang_switch ~override_meta ~all_predicates ~transition_length mode
                 (fun (d, single, s) ->
                   (* Check single constraints *)
                   (if selected s then not single else true)
-                  && satisfied d && s.source#is_ready)
+                  && satisfied d && s.source#is_ready ())
                 children))
       with Not_found -> None
 
diff --git a/src/core/operators/time_warp.ml b/src/core/operators/time_warp.ml
index fcf17672fd..821b8eacc6 100644
--- a/src/core/operators/time_warp.ml
+++ b/src/core/operators/time_warp.ml
@@ -127,7 +127,8 @@ module Buffer = struct
       method remaining =
         proceed c (fun () -> Generator.remaining (Lazy.force c.generator))
 
-      method is_ready = proceed c (fun () -> not c.buffering)
+      method private _is_ready ?frame:_ _ =
+        proceed c (fun () -> not c.buffering)
 
       method seek len =
         let len = min (Generator.length (Lazy.force c.generator)) len in
@@ -303,7 +304,10 @@ module AdaptativeBuffer = struct
       method stype = `Fallible
       method self_sync = (`Static, false)
       method remaining = proceed c (fun () -> MG.remaining c.mg)
-      method is_ready = proceed c (fun () -> not c.buffering)
+
+      method private _is_ready ?frame:_ _ =
+        proceed c (fun () -> not c.buffering)
+
       method ratio = proceed c (fun () -> c.rb_length /. prebuf)
 
       method buffer_duration =
diff --git a/src/core/operators/track/merge_metadata.ml b/src/core/operators/track/merge_metadata.ml
index c11a609384..ef22fc931d 100644
--- a/src/core/operators/track/merge_metadata.ml
+++ b/src/core/operators/track/merge_metadata.ml
@@ -36,8 +36,10 @@ class merge_metadata tracks =
       (Lazy.force self_sync_type, List.exists (fun s -> snd s#self_sync) sources)
 
     method abort_track = List.iter (fun s -> s#abort_track) sources
-    method private sources_ready = List.for_all (fun s -> s#is_ready) sources
-    method is_ready = List.for_all (fun s -> s#is_ready) sources
+
+    method private _is_ready ?frame () =
+      List.for_all (fun s -> s#is_ready ?frame ()) sources
+
     method seek len = len
     method seek_source = (self :> Source.source)
     method remaining = -1
@@ -54,9 +56,10 @@ class merge_metadata tracks =
       let pos = Frame.position buf in
       let max_pos =
         List.fold_left
-          (fun max_pos source ->
+          (fun max_pos (source : Source.source) ->
             let tmp_frame = self#track_frame source in
-            if source#is_ready && Frame.is_partial tmp_frame then (
+            if source#is_ready ~frame:tmp_frame () && Frame.is_partial tmp_frame
+            then (
               source#get tmp_frame;
               List.iter
                 (fun (p, m) ->
diff --git a/src/core/operators/track_map.ml b/src/core/operators/track_map.ml
index e5401a287c..1c00299fb2 100644
--- a/src/core/operators/track_map.ml
+++ b/src/core/operators/track_map.ml
@@ -31,7 +31,7 @@ class track_map ~name ~field ~fn s =
     method seek = s#seek
     method seek_source = s
     method self_sync = s#self_sync
-    method is_ready = s#is_ready
+    method private _is_ready = s#is_ready
     val mutable tmp_frame = None
 
     method tmp_frame =
diff --git a/src/core/operators/video_effects.ml b/src/core/operators/video_effects.ml
index 1c4890c65c..08d43be4c5 100644
--- a/src/core/operators/video_effects.ml
+++ b/src/core/operators/video_effects.ml
@@ -75,7 +75,7 @@ class virtual base ~name (source : source) f =
     method seek = source#seek
     method seek_source = source
     method self_sync = source#self_sync
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
 
     method private get_frame buf =
diff --git a/src/core/operators/video_fade.ml b/src/core/operators/video_fade.ml
index 67a4e5e7c8..99d0aa998b 100644
--- a/src/core/operators/video_fade.ml
+++ b/src/core/operators/video_fade.ml
@@ -31,7 +31,7 @@ class fade_in ?(meta = "liq_video_fade_in") duration fader fadefun source =
   object
     inherit operator ~name:"video.fade.in" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method remaining = source#remaining
     method self_sync = source#self_sync
@@ -96,7 +96,7 @@ class fade_out ?(meta = "liq_video_fade_out") duration fader fadefun source =
      * The value is set at the beginning of every track, depending on metadata. *)
     val mutable cur_length = None
     method remaining = source#remaining
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
 
     method private get_frame ab =
       let n = Frame.video_of_main source#remaining in
diff --git a/src/core/operators/window_op.ml b/src/core/operators/window_op.ml
index cfc26b3570..486235200c 100644
--- a/src/core/operators/window_op.ml
+++ b/src/core/operators/window_op.ml
@@ -30,7 +30,7 @@ class window mode duration source =
       operator [source] ~name:(match mode with RMS -> "rms" | Peak -> "peak") as super
 
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/outputs/output.ml b/src/core/outputs/output.ml
index 815f2a8233..d4e00ef7f6 100644
--- a/src/core/outputs/output.ml
+++ b/src/core/outputs/output.ml
@@ -96,11 +96,11 @@ class virtual output ~output_kind ?(name = "") ~infallible
               let t = Frame.seconds_of_main r in
               Printf.sprintf "%.2f" t)))
 
-    method is_ready =
+    method private _is_ready ?frame () =
       if infallible then (
-        assert source#is_ready;
+        assert (source#is_ready ?frame ());
         true)
-      else source#is_ready
+      else source#is_ready ?frame ()
 
     method remaining = source#remaining
     method abort_track = source#abort_track
@@ -129,7 +129,7 @@ class virtual output ~output_kind ?(name = "") ~infallible
          etc). *)
       source#get_ready ((self :> operator) :: activation);
       if infallible then
-        while not source#is_ready do
+        while not (source#is_ready ()) do
           self#log#important "Waiting for %S to be ready..." source#id;
           Thread.delay 1.
         done;
@@ -160,12 +160,12 @@ class virtual output ~output_kind ?(name = "") ~infallible
 
     method private output =
       self#has_ticked;
-      if self#is_ready && state <> `Stopped then
+      if self#is_ready ~frame:self#memo () && state <> `Stopped then
         start_stop#transition_to `Started;
       if start_stop#state = `Started then (
         (* Complete filling of the frame *)
         let get_count = ref 0 in
-        while Frame.is_partial self#memo && self#is_ready do
+        while Frame.is_partial self#memo && self#is_ready ~frame:self#memo () do
           incr get_count;
           if !get_count > Lazy.force Frame.size then
             self#log#severe
diff --git a/src/core/outputs/output.mli b/src/core/outputs/output.mli
index cb2707504f..6dcd2f858e 100644
--- a/src/core/outputs/output.mli
+++ b/src/core/outputs/output.mli
@@ -41,7 +41,7 @@ class virtual output :
        method output : unit
        method private get_frame : Frame.t -> unit
        method abort_track : unit
-       method is_ready : bool
+       method private _is_ready : ?frame:Frame.t -> unit -> bool
        method state : Start_stop.state
        method transition_to : Start_stop.state -> unit
        method seek : int -> int
diff --git a/src/core/source.ml b/src/core/source.ml
index 06326aa5dd..d740b197de 100644
--- a/src/core/source.ml
+++ b/src/core/source.ml
@@ -599,10 +599,17 @@ class virtual operator ?pos ?(name = "src") sources =
            source. *)
     method virtual seek_source : source
 
-    (* Is there some data available for the next [get]?
-       Must always be true while playing a track, i.e. all tracks
-       must be properly ended. *)
-    method virtual is_ready : bool
+    (* Underlying source implementation for [is_ready].
+       should return [true] when the source can produce
+       fresh data. *)
+    method virtual private _is_ready : ?frame:Frame.t -> unit -> bool
+
+    method is_ready ?frame () =
+      match frame with
+        | None -> self#_is_ready ?frame ()
+        | Some frame ->
+            (caching && Frame.position frame < Frame.position self#memo)
+            || self#_is_ready ~frame ()
 
     (* If possible, end the current track.
        Typically, that signal is just re-routed, or makes the next file
@@ -758,7 +765,7 @@ class virtual operator ?pos ?(name = "src") sources =
          track, otherwise the track will be ended without the source noticing! *)
       let silent_end_track () = Frame.add_break buf (Frame.position buf) in
       if not caching then
-        if not self#is_ready then silent_end_track ()
+        if not (self#_is_ready ~frame:buf ()) then silent_end_track ()
         else (
           let b = Frame.breaks buf in
           self#instrumented_get_frame buf;
@@ -773,7 +780,7 @@ class virtual operator ?pos ?(name = "src") sources =
         let memo = self#memo in
         try Frame.get_chunk buf memo
         with Frame.No_chunk ->
-          if not self#is_ready then silent_end_track ()
+          if not (self#_is_ready ~frame:buf ()) then silent_end_track ()
           else (
             (* [memo] has nothing new for [buf]. Feed [memo] and try again *)
             let b = Frame.breaks memo in
diff --git a/src/core/source.mli b/src/core/source.mli
index 3af986630e..a2b8ba95b2 100644
--- a/src/core/source.mli
+++ b/src/core/source.mli
@@ -191,8 +191,17 @@ class virtual source :
            source. *)
        method virtual seek_source : source
 
-       (** [is_ready] tells you if [get] can be called. *)
-       method virtual is_ready : bool
+       (** [is_ready] tells you if [get] can be called.
+           Frame argument is optional. With no frame, the
+	   function tells you if the source can produce
+	   fresh data. With a frame, it tells you if the
+	   source can fill the frame from its current position,
+	   potentially using cached data when the source is
+	   caching. *)
+       method is_ready : ?frame:Frame.t -> unit -> bool
+
+       (* Internal implementation of [is_ready]. *)
+       method virtual private _is_ready : ?frame:Frame.t -> unit -> bool
 
        (** [get buf] asks the source to fill the buffer [buf] if possible.
            The [get] call is partial when the buffer is not completely filled.
diff --git a/src/core/sources/blank.ml b/src/core/sources/blank.ml
index e14ea5f9a5..1544d93c47 100644
--- a/src/core/sources/blank.ml
+++ b/src/core/sources/blank.ml
@@ -33,7 +33,7 @@ class blank duration =
 
     method remaining = remaining
     method stype = `Infallible
-    method is_ready = true
+    method private _is_ready ?frame:_ _ = true
     method self_sync = (`Static, false)
     method seek x = x
     method seek_source = (self :> Source.source)
diff --git a/src/core/sources/debug_sources.ml b/src/core/sources/debug_sources.ml
index 056060c31a..9d4c379af5 100644
--- a/src/core/sources/debug_sources.ml
+++ b/src/core/sources/debug_sources.ml
@@ -26,7 +26,7 @@ class fail name =
     inherit Source.no_seek
     method seek_source = (self :> Source.source)
     method stype = `Fallible
-    method is_ready = false
+    method private _is_ready ?frame:_ _ = false
     method self_sync = (`Static, false)
     method remaining = 0
     method abort_track = ()
diff --git a/src/core/sources/generated.ml b/src/core/sources/generated.ml
index cd23d7ef45..aa3484fc51 100644
--- a/src/core/sources/generated.ml
+++ b/src/core/sources/generated.ml
@@ -50,7 +50,7 @@ class virtual source ?(seek = false) ?(replay_meta = false) ~bufferize
     method private length = Generator.length self#buffer
     val mutable last_buffering_warning = -1
 
-    method is_ready =
+    method private _is_ready ?frame:_ _ =
       let r = self#length in
       if buffering then (
         (* We have some data, but not enough for safely starting to play it. *)
diff --git a/src/core/sources/harbor_input.ml b/src/core/sources/harbor_input.ml
index 3e1fe097d5..07e83d11af 100644
--- a/src/core/sources/harbor_input.ml
+++ b/src/core/sources/harbor_input.ml
@@ -60,7 +60,8 @@ class http_input_server ~pos ~transport ~dumpfile ~logfile ~bufferize ~max ~icy
         | None -> "no source client connected"
 
     method private output =
-      if self#is_ready && AFrame.is_partial self#memo then self#get self#memo
+      if self#is_ready ~frame:self#memo () && AFrame.is_partial self#memo then
+        self#get self#memo
 
     method reset = self#disconnect ~lock:true
     method buffer_length_cmd = Frame.seconds_of_audio self#length
diff --git a/src/core/sources/request_simple.ml b/src/core/sources/request_simple.ml
index faa998989e..25fa94deeb 100644
--- a/src/core/sources/request_simple.ml
+++ b/src/core/sources/request_simple.ml
@@ -148,8 +148,8 @@ class dynamic ~retry_delay ~available (f : Lang.value) prefetch timeout =
 
     val mutable retry_status = None
 
-    method! is_ready =
-      match (super#is_ready, retry_status) with
+    method! _is_ready ?frame () =
+      match (super#_is_ready ?frame (), retry_status) with
         | true, _ -> true
         | false, Some d when Unix.gettimeofday () < d -> false
         | false, _ ->
diff --git a/src/core/sources/request_source.ml b/src/core/sources/request_source.ml
index 577507e1a7..4e168f821c 100644
--- a/src/core/sources/request_source.ml
+++ b/src/core/sources/request_source.ml
@@ -102,7 +102,7 @@ class once ~name ~timeout request =
         remaining <- 0;
         if forced then must_fail <- true else over <- true)
 
-    method is_ready = not over
+    method private _is_ready ?frame:_ _ = not over
 
     method private get_frame buf =
       if must_fail then (
@@ -222,7 +222,7 @@ class virtual unqueued ~name =
 
     (** Now we can write the source's methods. *)
 
-    method is_ready =
+    method private _is_ready ?frame:_ _ =
       Tutils.mutexify plock
         (fun () ->
           current <> None || must_fail || try self#begin_track with _ -> false)
diff --git a/src/core/sources/request_source.mli b/src/core/sources/request_source.mli
index ec3b02972b..db1c01b1c7 100644
--- a/src/core/sources/request_source.mli
+++ b/src/core/sources/request_source.mli
@@ -37,7 +37,7 @@ class once :
        inherit Source.source
        method stype : [ `Fallible | `Infallible ]
        method self_sync : Source.self_sync
-       method is_ready : bool
+       method private _is_ready : ?frame:Frame.t -> unit -> bool
        method request : Request.t
        method remaining : int
        method private get_frame : Frame.t -> unit
@@ -56,7 +56,7 @@ class virtual unqueued :
          [ `Empty | `Request of Request.t | `Retry of unit -> float ]
 
        inherit Source.source
-       method is_ready : bool
+       method private _is_ready : ?frame:Frame.t -> unit -> bool
        method private get_frame : Frame.t -> unit
        method abort_track : unit
        method remaining : int
diff --git a/src/core/sources/synthesized.ml b/src/core/sources/synthesized.ml
index 430135626c..766f9988fb 100644
--- a/src/core/sources/synthesized.ml
+++ b/src/core/sources/synthesized.ml
@@ -30,7 +30,7 @@ class virtual source ?name ~seek duration =
     inherit Source.source ?name ()
     method stype = if track_size = None then `Infallible else `Fallible
     val mutable remaining = track_size
-    method is_ready = remaining <> Some 0
+    method private _is_ready ?frame:_ _ = remaining <> Some 0
     method seek x = if seek then x else 0
     method seek_source = (self :> Source.source)
     method self_sync = (`Static, false)
diff --git a/src/core/synth/dssi_op.ml b/src/core/synth/dssi_op.ml
index ae6d16de6c..417d907996 100644
--- a/src/core/synth/dssi_op.ml
+++ b/src/core/synth/dssi_op.ml
@@ -55,7 +55,7 @@ class dssi ?chan plugin descr outputs params source =
     method seek_source = source
     method stype = source#stype
     method remaining = source#remaining
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method self_sync = source#self_sync
     method abort_track = source#abort_track
 
diff --git a/src/core/synth/keyboard.ml b/src/core/synth/keyboard.ml
index 67340ea4d9..34c0d0d24a 100644
--- a/src/core/synth/keyboard.ml
+++ b/src/core/synth/keyboard.ml
@@ -58,13 +58,14 @@ class keyboard =
     inherit Source.no_seek
     method seek_source = (self :> Source.source)
     method stype = `Infallible
-    method is_ready = true
+    method private _is_ready ?frame:_ _ = true
     method remaining = -1
     method abort_track = ()
     method self_sync = (`Static, false)
 
     method output =
-      if self#is_ready && AFrame.is_partial self#memo then self#get self#memo
+      if self#is_ready ~frame:self#memo () && AFrame.is_partial self#memo then
+        self#get self#memo
 
     val mutable ev = MIDI.create (MFrame.size ())
     val ev_m = Mutex.create ()
diff --git a/src/core/synth/keyboard_sdl.ml b/src/core/synth/keyboard_sdl.ml
index 7735e60e9e..018fefeabd 100644
--- a/src/core/synth/keyboard_sdl.ml
+++ b/src/core/synth/keyboard_sdl.ml
@@ -89,13 +89,14 @@ class keyboard velocity =
     inherit Source.no_seek
     method seek_source = (self :> Source.source)
     method stype = `Infallible
-    method is_ready = true
+    method private _is_ready ?frame:_ _ = true
     method remaining = -1
     method abort_track = ()
     method self_sync = (`Static, false)
 
     method output =
-      if self#is_ready && AFrame.is_partial self#memo then self#get self#memo
+      if self#is_ready ~frame:self#memo () && AFrame.is_partial self#memo then
+        self#get self#memo
 
     val mutable window = None
 
diff --git a/src/core/synth/synth_op.ml b/src/core/synth/synth_op.ml
index dd903e22de..8c75e1c694 100644
--- a/src/core/synth/synth_op.ml
+++ b/src/core/synth/synth_op.ml
@@ -30,7 +30,7 @@ class synth (synth : Synth.synth) (source : source) chan volume =
     method stype = source#stype
     method self_sync = source#self_sync
     method remaining = source#remaining
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method abort_track = source#abort_track
     method seek = source#seek
     method seek_source = source
diff --git a/src/core/tools/producer_consumer.ml b/src/core/tools/producer_consumer.ml
index 2d61b4108a..b7958750ab 100644
--- a/src/core/tools/producer_consumer.ml
+++ b/src/core/tools/producer_consumer.ml
@@ -54,8 +54,8 @@ class consumer ?(always_enabled = false) ~write_frame ~name ~source () =
     method start = ()
     method stop = write_frame producer_buffer `Flush
 
-    method! is_ready =
-      super#is_ready
+    method! _is_ready ?frame () =
+      super#_is_ready ?frame ()
       && (Clock.get self#clock)#is_attached (self :> Source.active_source)
 
     method! output = if always_enabled || output_enabled then super#output
@@ -99,7 +99,8 @@ class producer ?pos ?create_known_clock ~check_self_sync ~consumers ~name () =
         | -1, r -> r
         | r, _ -> r
 
-    method is_ready = List.for_all (fun c -> c#is_ready) consumers
+    method private _is_ready ?frame () =
+      List.for_all (fun c -> c#is_ready ?frame ()) consumers
 
     method! wake_up a =
       super#wake_up a;
@@ -120,7 +121,8 @@ class producer ?pos ?create_known_clock ~check_self_sync ~consumers ~name () =
       let b = Frame.breaks buf in
       List.iter (fun c -> c#set_output_enabled true) consumers;
       while
-        Generator.length self#buffer < Lazy.force Frame.size && self#is_ready
+        Generator.length self#buffer < Lazy.force Frame.size
+        && self#is_ready ~frame:self#buffer ()
       do
         self#child_tick
       done;
diff --git a/src/core/tools/start_stop.ml b/src/core/tools/start_stop.ml
index 7b673f01d8..86b7d4c0c2 100644
--- a/src/core/tools/start_stop.ml
+++ b/src/core/tools/start_stop.ml
@@ -78,7 +78,7 @@ class virtual active_source ?get_clock ~name ~clock_safe
     method stype = if fallible then `Fallible else `Infallible
     method! private wake_up _ = if autostart then base#transition_to `Started
     method! private sleep = base#transition_to `Stopped
-    method is_ready = state = `Started
+    method private _is_ready ?frame:_ _ = state = `Started
     val mutable clock = None
 
     method private get_clock =
@@ -99,7 +99,8 @@ class virtual active_source ?get_clock ~name ~clock_safe
     method virtual private memo : Frame.t
 
     method private output =
-      if self#is_ready && AFrame.is_partial self#memo then self#get self#memo
+      if self#is_ready ~frame:self#memo () && AFrame.is_partial self#memo then
+        self#get self#memo
   end
 
 let base_proto ~label =
diff --git a/src/core/visualization/midimeter.ml b/src/core/visualization/midimeter.ml
index 877d2d8633..5aea29c149 100644
--- a/src/core/visualization/midimeter.ml
+++ b/src/core/visualization/midimeter.ml
@@ -27,7 +27,7 @@ class midimeter source =
   object
     inherit operator ~name:"midi.inspect" [source]
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method self_sync = source#self_sync
diff --git a/src/core/visualization/video_volume.ml b/src/core/visualization/video_volume.ml
index ba96713869..73e05cab1f 100644
--- a/src/core/visualization/video_volume.ml
+++ b/src/core/visualization/video_volume.ml
@@ -33,7 +33,7 @@ class visu source =
   object (self)
     inherit operator ~name:"video.volume" [source] as super
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method self_sync = source#self_sync
diff --git a/src/core/visualization/vis_volume.ml b/src/core/visualization/vis_volume.ml
index bc9169bffa..de3ef72bf9 100644
--- a/src/core/visualization/vis_volume.ml
+++ b/src/core/visualization/vis_volume.ml
@@ -33,7 +33,7 @@ class vumeter ~kind source =
     inherit operator ~name:"visu.volume" kind [source] as super
     inherit no_seek
     method stype = source#stype
-    method is_ready = source#is_ready
+    method private _is_ready = source#is_ready
     method remaining = source#remaining
     method abort_track = source#abort_track
     method self_sync = source#self_sync
diff --git a/tests/core/output_test.ml b/tests/core/output_test.ml
index b5a41ddd38..bca49d1bab 100644
--- a/tests/core/output_test.ml
+++ b/tests/core/output_test.ml
@@ -9,7 +9,7 @@ class dummy ~autostart ~on_start source =
     method test_wake_up = self#wake_up []
     val mutable test_is_ready = false
     method test_set_is_ready = test_is_ready <- true
-    method! is_ready = test_is_ready
+    method! is_ready ?frame:_ _ = test_is_ready
     method test_output = self#output
   end
 
@@ -31,12 +31,12 @@ let () =
   let o = new dummy ~on_start ~autostart:true failed in
   let clock = Clock.clock ~start:false "source" in
   Clock.unify ~pos:o#pos o#clock (Clock.create_known clock);
-  assert (not o#is_ready);
+  assert (not (o#is_ready ()));
   o#content_type_computation_allowed;
   o#test_wake_up;
   assert (not !started);
   o#test_set_is_ready;
-  assert o#is_ready;
+  assert (o#is_ready ());
   o#test_output;
   assert !started;
   ()