added comments

packager/media/formats/mp2t/ts_muxer.cc

@@ -34,6 +34,8 @@ Status TsMuxer::Finalize() {
 
 Status TsMuxer::AddSample(size_t stream_id, const MediaSample& sample) {
   DCHECK_EQ(stream_id, 0u);
+  // The duration of the first sample may have been adjusted, so use 
+  // the duration of the second sample instead.
   if (num_samples_ < 2) {
     sample_durations_[num_samples_] = sample.duration() * kTsTimescale / 
                                       streams().front()->time_scale();

packager/media/formats/mp4/segmenter.cc

@@ -138,6 +138,8 @@ Status Segmenter::AddSample(size_t stream_id, const MediaSample& sample) {
   if (!status.ok())
     return status;
 
+  // The duration of the first sample may have been adjusted, so use 
+  // the duration of the second sample instead.
   if (num_samples_ < 2) {
     sample_durations_[num_samples_] = sample.duration();
     num_samples_++;

packager/media/formats/webm/segmenter.cc

@@ -161,6 +161,8 @@ Status Segmenter::Finalize() {
 Status Segmenter::AddSample(const MediaSample& source_sample) {
   std::shared_ptr<MediaSample> sample(source_sample.Clone());
 
+  // The duration of the first sample may have been adjusted, so use 
+  // the duration of the second sample instead.
   if (num_samples_ < 2) {
     sample_durations_[num_samples_] = sample->duration();
     if (num_samples_ == 0)

packager/media/formats/webm/segmenter.h

@@ -139,7 +139,7 @@ class Segmenter {
   uint64_t progress_target_ = 0;
   uint64_t accumulated_progress_ = 0;
   uint64_t first_timestamp_ = 0;
-  uint32_t sample_durations_[2] = {0u, 0u};
+  int64_t sample_durations_[2] = {0, 0};
   size_t num_samples_ = 0;
   // The position (in bytes) of the start of the Segment payload in the init
   // file.  This is also the size of the header before the SeekHead.