[Chromecast] Improve rendering delay accuracy by tracking partial samples

The resampler can partially consume audio samples (since when resampling,
one output sample can correspond to fractional input samples). By keeping
track of the partially-consumed samples, we can improve the accuracy of
the estimated rendering delay.

BUG=

Review URL: https://codereview.chromium.org/1809203003

Cr-Commit-Position: refs/heads/master@{#381832}

2 files changed, 10 insertions, 7 deletions

diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
index 041ae4a..a1f924b 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
@@ -147,7 +147,8 @@ void StreamMixerAlsaInputImpl::PrepareToDelete(
       fade_frames_remaining_ = queued_frames_including_resampler_;
     } else if (state_ == kStateNormalPlayback) {
       fade_out_frames_total_ =
-          std::min(queued_frames_including_resampler_, NormalFadeFrames());
+          std::min(static_cast<int>(queued_frames_including_resampler_),
+                   NormalFadeFrames());
       fade_frames_remaining_ = fade_out_frames_total_;
     }
   }
@@ -199,9 +200,9 @@ MediaPipelineBackendAlsa::RenderingDelay StreamMixerAlsaInputImpl::QueueData(
   }
 
   MediaPipelineBackendAlsa::RenderingDelay delay = mixer_rendering_delay_;
-  delay.delay_microseconds +=
-      static_cast<int64_t>(queued_frames_including_resampler_) *
-      base::Time::kMicrosecondsPerSecond / input_samples_per_second_;
+  delay.delay_microseconds += static_cast<int64_t>(
+      queued_frames_including_resampler_ * base::Time::kMicrosecondsPerSecond /
+      input_samples_per_second_);
   return delay;
 }
 
@@ -226,7 +227,8 @@ void StreamMixerAlsaInputImpl::DidQueueData(bool end_of_stream) {
 void StreamMixerAlsaInputImpl::AfterWriteFrames(
     const MediaPipelineBackendAlsa::RenderingDelay& mixer_rendering_delay) {
   DCHECK(mixer_task_runner_->BelongsToCurrentThread());
-  int resampler_queued_frames = (resampler_ ? resampler_->BufferedFrames() : 0);
+  double resampler_queued_frames =
+      (resampler_ ? resampler_->BufferedFrames() : 0);
 
   bool queued_more_data = false;
   MediaPipelineBackendAlsa::RenderingDelay total_delay;
@@ -267,7 +269,8 @@ int StreamMixerAlsaInputImpl::MaxReadSize() {
   {
     base::AutoLock lock(queue_lock_);
     if (state_ == kStateGotEos)
-      return std::max(queued_frames_including_resampler_, kDefaultReadSize);
+      return std::max(static_cast<int>(queued_frames_including_resampler_),
+                      kDefaultReadSize);
     queued_frames = queued_frames_;
   }
 
diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h
index 8468319..f31e1fa 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h
@@ -152,7 +152,7 @@ class StreamMixerAlsaInputImpl : public StreamMixerAlsa::InputQueue {
   scoped_refptr<DecoderBufferBase> pending_data_;
   std::deque<scoped_refptr<DecoderBufferBase>> queue_;
   int queued_frames_;
-  int queued_frames_including_resampler_;
+  double queued_frames_including_resampler_;
   MediaPipelineBackendAlsa::RenderingDelay mixer_rendering_delay_;
   // End of members that queue_lock_ controls access for.