Add Stop() to AudioDecoder.

media/filters/ffmpeg_audio_decoder.cc

Index: media/filters/ffmpeg_audio_decoder.cc
diff --git a/media/filters/ffmpeg_audio_decoder.cc b/media/filters/ffmpeg_audio_decoder.cc
index a0e5889eff11aca7e6c84c6bdbf26080ca2fd8c0..546edf5c1de7288498728d59049f3deb4f43b215 100644
--- a/media/filters/ffmpeg_audio_decoder.cc
+++ b/media/filters/ffmpeg_audio_decoder.cc
@@ -115,6 +115,7 @@ void FFmpegAudioDecoder::Read(const ReadCB& read_cb) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(!read_cb.is_null());
   CHECK(read_cb_.is_null()) << "Overlapping decodes are not supported.";
+  DCHECK(stop_cb_.is_null());

[xhwang, 2014/01/10 18:58:51]

nit: check reset_cb as well? 

 
   read_cb_ = BindToCurrentLoop(read_cb);
 
@@ -147,20 +148,24 @@ int FFmpegAudioDecoder::samples_per_second() {
 
 void FFmpegAudioDecoder::Reset(const base::Closure& closure) {
   DCHECK(task_runner_->BelongsToCurrentThread());
-  base::Closure reset_cb = BindToCurrentLoop(closure);
+  reset_cb_ = BindToCurrentLoop(closure);
 
-  avcodec_flush_buffers(codec_context_.get());
-  ResetTimestampState();
-  queued_audio_.clear();
-  reset_cb.Run();
+  if (read_cb_.is_null())
+    DoReset();
+  // Otherwise a demuxer read is pending, we'll wait until it finishes.
 }
 
-FFmpegAudioDecoder::~FFmpegAudioDecoder() {
-  // TODO(scherkus): should we require Stop() to be called? this might end up
-  // getting called on a random thread due to refcounting.
-  ReleaseFFmpegResources();
+void FFmpegAudioDecoder::Stop(const base::Closure& closure) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  stop_cb_ = BindToCurrentLoop(closure);
+
+  if (read_cb_.is_null())
+    DoStop();

[xhwang, 2014/01/10 18:58:51]

What if we are calling Stop() during a pending reset (no pending read)? For
example:
Read()
read done
Reset()
Stop()
reset done
stop done
The order of "reset done" and "stop done" should be determinstic.

+  // Otherwise a demuxer read is pending, we'll wait until it finishes.
 }
 
+FFmpegAudioDecoder::~FFmpegAudioDecoder() {}
+
 int FFmpegAudioDecoder::GetAudioBuffer(AVCodecContext* codec,
                                        AVFrame* frame,
                                        int flags) {
@@ -226,6 +231,26 @@ int FFmpegAudioDecoder::GetAudioBuffer(AVCodecContext* codec,
   return 0;
 }
 
+void FFmpegAudioDecoder::DoStop() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(!stop_cb_.is_null());
+

[xhwang, 2014/01/10 18:58:51]

check that no read and no reset is pending when we DoStop.

+  ResetTimestampState();
+  queued_audio_.clear();
+  ReleaseFFmpegResources();
+  base::ResetAndReturn(&stop_cb_).Run();
+}
+
+void FFmpegAudioDecoder::DoReset() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(!reset_cb_.is_null());

[xhwang, 2014/01/10 18:58:51]

check that no read is pending when we DoReset.

+
+  avcodec_flush_buffers(codec_context_.get());
+  ResetTimestampState();
+  queued_audio_.clear();
+  base::ResetAndReturn(&reset_cb_).Run();
+}
+
 void FFmpegAudioDecoder::ReadFromDemuxerStream() {
   DCHECK(!read_cb_.is_null());
   demuxer_stream_->Read(base::Bind(
@@ -240,6 +265,22 @@ void FFmpegAudioDecoder::BufferReady(
   DCHECK(queued_audio_.empty());
   DCHECK_EQ(status != DemuxerStream::kOk, !input.get()) << status;
 
+  // Stop() is pending, we'll ignore the buffer we just got, fire read_cb_, and
+  // complete the Stop.
+  if (!stop_cb_.is_null()) {
+    base::ResetAndReturn(&read_cb_).Run(kAborted, NULL);
+    DoStop();
+    return;
+  }
+
+  // Reset() is pending, we'll ignore the buffer we just got, fire read_cb_, and
+  // complete the Reset.
+  if (!reset_cb_.is_null()) {
+    base::ResetAndReturn(&read_cb_).Run(kAborted, NULL);
+    DoReset();
+    return;
+  }
+

[xhwang, 2014/01/10 18:58:51]

If Stop() is called during pending reset, we should DoReset() first, then
DoStop() so that reset cb is always fired before the stop cb.

Background: All these fancy logic used to live in FFmpegVideoDecoder as well :)

https://chromiumcodereview.appspot.com/16274005

When you detach the decoder from the DemuxerStream, most of these will go away.

   if (status == DemuxerStream::kAborted) {
     DCHECK(!input.get());
     base::ResetAndReturn(&read_cb_).Run(kAborted, NULL);