Add an option to specify FFmpeg encoding parameters

c_src/membrane_h264_ffmpeg_plugin/encoder.c

@@ -55,8 +55,8 @@ static void set_x264_defaults(AVDictionary **params, char *preset) {
 UNIFEX_TERM create(UnifexEnv *env, int width, int height, char *pix_fmt,
                    char *preset, char *tune, char *profile, int max_b_frames,
                    int gop_size, int timebase_num, int timebase_den, int crf,
-                   int sc_threshold, ffmpeg_option *ffmpeg_options,
-                   unsigned int ffmpeg_options_length) {
+                   int sc_threshold, ffmpeg_param *ffmpeg_params,
+                   unsigned int ffmpeg_params_length) {
   UNIFEX_TERM res;
   AVDictionary *params = NULL;
   State *state = unifex_alloc_state(env);
@@ -106,8 +106,8 @@ UNIFEX_TERM create(UnifexEnv *env, int width, int height, char *pix_fmt,
 
   set_x264_defaults(&params, preset);
 
-  for (unsigned int i = 0; i < ffmpeg_options_length; i++) {
-    av_dict_set(&params, ffmpeg_options[i].key, ffmpeg_options[i].value, 0);
+  for (unsigned int i = 0; i < ffmpeg_params_length; i++) {
+    av_dict_set(&params, ffmpeg_params[i].key, ffmpeg_params[i].value, 0);
   }
 
   av_dict_set(&params, "preset", preset, 0);

c_src/membrane_h264_ffmpeg_plugin/encoder.spec.exs

@@ -3,7 +3,7 @@ module Membrane.H264.FFmpeg.Encoder.Native
 state_type "State"
 
 type(
-  ffmpeg_option :: %Membrane.H264.FFmpeg.Encoder.FFmpegOption{
+  ffmpeg_param :: %Membrane.H264.FFmpeg.Encoder.FFmpegParam{
     key: string,
     value: string
   }
@@ -22,7 +22,7 @@ spec create(
        timebase_den :: int,
        crf :: int,
        sc_threshold :: int,
-       ffmpeg_options :: [ffmpeg_option]
+       ffmpeg_params :: [ffmpeg_param]
      ) :: {:ok :: label, state} | {:error :: label, reason :: atom}
 
 spec get_frame_size(state) :: {:ok :: label, frame_size :: int} | {:error :: label}

lib/membrane_h264_ffmpeg/encoder.ex

@@ -12,6 +12,7 @@ defmodule Membrane.H264.FFmpeg.Encoder do
   Please check `t:t/0` for available options.
   """
   use Membrane.Filter
+  require Membrane.Logger, as: Logger
   alias __MODULE__.Native
   alias Membrane.Buffer
   alias Membrane.H264
@@ -122,22 +123,29 @@ defmodule Membrane.H264.FFmpeg.Encoder do
                 """,
                 default: @default_sc_threshold
               ],
-              ffmpeg_options: [
+              ffmpeg_params: [
                 spec: %{String.t() => String.t()},
                 description: """
-                A map with options that will be passed to the encoder.
+                A map with parameters that are passed to the encoder.
+
+                You can use options from: https://ffmpeg.org/ffmpeg-codecs.html#libx264_002c-libx264rgb
+                and https://ffmpeg.org/ffmpeg-codecs.html#Codec-Options
+                Remember not to overwrite options that are available as a separate module options
+                (like `sc_threshold` or `crf`).
                 """,
                 default: %{}
               ]
 
-  defmodule FFmpegOption do
+  defmodule FFmpegParam do
     @moduledoc false
     @enforce_keys [:key, :value]
     defstruct @enforce_keys
   end
 
   @impl true
   def handle_init(_ctx, opts) do
+    warn_if_ffmpeg_params_overwrite_module_options(opts.ffmpeg_params)
+
     state =
       opts
       |> Map.put(:encoder_ref, nil)
@@ -178,8 +186,8 @@ defmodule Membrane.H264.FFmpeg.Encoder do
         frames_per_second when is_integer(frames_per_second) -> {1, frames_per_second}
       end
 
-    ffmpeg_options =
-      Enum.map(state.ffmpeg_options, fn {key, value} -> %FFmpegOption{key: key, value: value} end)
+    ffmpeg_params =
+      Enum.map(state.ffmpeg_params, fn {key, value} -> %FFmpegParam{key: key, value: value} end)
 
     with buffers <- flush_encoder_if_exists(state),
          {:ok, new_encoder_ref} <-
@@ -196,7 +204,7 @@ defmodule Membrane.H264.FFmpeg.Encoder do
              timebase_den,
              state.crf,
              state.sc_threshold,
-             ffmpeg_options
+             ffmpeg_params
            ) do
       stream_format = create_new_stream_format(stream_format, state)
       actions = buffers ++ [stream_format: stream_format]
@@ -274,4 +282,24 @@ defmodule Membrane.H264.FFmpeg.Encoder do
       other -> other
     end
   end
+
+  defp warn_if_ffmpeg_params_overwrite_module_options(ffmpeg_params) do
+    params_to_options_mapping = %{
+      "crf" => "crf",
+      "preset" => "preset",
+      "profile" => "profile",
+      "tune" => "tune",
+      "max_b_frames" => "max_b_frames",
+      "g" => "gop_size",
+      "sc_threshold" => "sc_threshold"
+    }
+
+    Map.keys(ffmpeg_params)
+    |> Enum.filter(fn param_name -> params_to_options_mapping[param_name] != nil end)
+    |> Enum.each(fn param_name ->
+      Logger.warning(
+        "The parameter: `#{param_name}` you provided in the `ffmpeg_params` map overwrites the setting from the modules option: `#{params_to_options_mapping[param_name]}`."
+      )
+    end)
+  end
 end