[Chromecast] Add support for different playback rates to ALSA backend

chromecast/media/cma/backend/alsa/audio_decoder_alsa.h

Index: chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
diff --git a/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h b/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
index 04c963f00603125c14fc093e83ccddb113b886b6..18d271c6b7aea7f5ff36ec198844f7d8c34b7364 100644
--- a/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
+++ b/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
@@ -5,6 +5,8 @@
 #ifndef CHROMECAST_MEDIA_CMA_BACKEND_ALSA_AUDIO_DECODER_ALSA_H_
 #define CHROMECAST_MEDIA_CMA_BACKEND_ALSA_AUDIO_DECODER_ALSA_H_
 
+#include <deque>
+
 #include "base/bind.h"
 #include "base/location.h"
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h"
@@ -17,6 +19,11 @@ namespace base {
 class SingleThreadTaskRunner;
 }  // namespace base
 
+namespace media {
+class AudioBus;
+class AudioRendererAlgorithm;
+}  // namespace media
+
 namespace chromecast {
 namespace media {
 class DecoderBufferBase;
@@ -35,6 +42,7 @@ class AudioDecoderAlsa : public MediaPipelineBackend::AudioDecoder,
   void Stop();
   bool Pause();
   bool Resume();
+  bool SetPlaybackRate(float rate);
 
   int64_t current_pts() const { return current_pts_; }
 
@@ -48,6 +56,14 @@ class AudioDecoderAlsa : public MediaPipelineBackend::AudioDecoder,
   RenderingDelay GetRenderingDelay() override;
 
  private:
+  struct RateShifterInfo {
+    RateShifterInfo(float playback_rate);

[slan, 2016/12/07 00:22:27]

nit: explicit

Also, can we do a default ctor here?

[kmackay, 2016/12/07 22:59:58]

Added explicit; I don't think a default constructor makes sense here though.

[slan, 2016/12/09 00:05:31]

Yeah, I'm silly.

+
+    double rate;
+    double input_frames;
+    int64_t output_frames;
+  };
+
   // StreamMixerAlsaInput::Delegate implementation:
   void OnWritePcmCompletion(BufferStatus status,
                             const RenderingDelay& delay) override;
@@ -55,10 +71,13 @@ class AudioDecoderAlsa : public MediaPipelineBackend::AudioDecoder,
 
   void CleanUpPcm();
   void CreateDecoder();
+  void CreateRateShifter(int samples_per_second);
   void OnDecoderInitialized(bool success);
   void OnBufferDecoded(uint64_t input_bytes,
                        CastAudioDecoder::Status status,
                        const scoped_refptr<DecoderBufferBase>& decoded);
+  void PushRateShifted();
+  void PushMorePcm();
   void RunEos();
   bool BypassDecoder() const;
   bool ShouldStartClock() const;
@@ -69,17 +88,25 @@ class AudioDecoderAlsa : public MediaPipelineBackend::AudioDecoder,
   MediaPipelineBackend::Decoder::Delegate* delegate_;
 
   Statistics stats_;
-  bool is_eos_;
+
+  bool pending_write_pcm_;

[halliwell, 2016/12/06 17:27:59]

Seems like this is mostly redundant (corresponds to pending_output_frames_ being
non-zero, modulo setting that for eos case)?

[slan, 2016/12/07 00:22:27]

Yes, after grepping for this value, it does seem that you could check
pending_output_frames_ != 0 instead.

[kmackay, 2016/12/07 22:59:58]

input_frames can be 0 sometimes. I added a (negative) constant to check for
instead.

+  bool pending_buffer_complete_;
+  bool got_eos_;
+  bool pushed_eos_;
   bool error_;
 
   AudioConfig config_;
   std::unique_ptr<CastAudioDecoder> decoder_;
 
+  std::unique_ptr<::media::AudioRendererAlgorithm> rate_shifter_;

[halliwell, 2016/12/06 17:27:59]

nit, should be including <memory>

[kmackay, 2016/12/07 22:59:58]

Done.

+  std::deque<RateShifterInfo> rate_shifter_info_;
+  std::unique_ptr<::media::AudioBus> rate_shifter_output_;
+
   int64_t current_pts_;
-  int64_t last_buffer_pts_;
 
   std::unique_ptr<StreamMixerAlsaInput> mixer_input_;
   RenderingDelay last_known_delay_;
+  int64_t pending_output_frames_;
   float volume_multiplier_;
 
   base::WeakPtrFactory<AudioDecoderAlsa> weak_factory_;