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

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

Index: chromecast/media/cma/backend/alsa/audio_decoder_alsa.cc
diff --git a/chromecast/media/cma/backend/alsa/audio_decoder_alsa.cc b/chromecast/media/cma/backend/alsa/audio_decoder_alsa.cc
index cb6014f4b641d5e6b795a3083f63fb2a522f3046..4ed98894aa6d1cbd8c557e8e5833573f74babc19 100644
--- a/chromecast/media/cma/backend/alsa/audio_decoder_alsa.cc
+++ b/chromecast/media/cma/backend/alsa/audio_decoder_alsa.cc
@@ -15,8 +15,15 @@
 #include "base/trace_event/trace_event.h"
 #include "chromecast/base/task_runner_impl.h"
 #include "chromecast/media/cma/backend/alsa/media_pipeline_backend_alsa.h"
+#include "chromecast/media/cma/base/decoder_buffer_adapter.h"
 #include "chromecast/media/cma/base/decoder_buffer_base.h"
 #include "chromecast/public/media/cast_decoder_buffer.h"
+#include "media/base/audio_buffer.h"
+#include "media/base/audio_bus.h"
+#include "media/base/channel_layout.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/sample_format.h"
+#include "media/filters/audio_renderer_algorithm.h"
 
 #define TRACE_FUNCTION_ENTRY0() TRACE_EVENT0("cma", __FUNCTION__)
 
@@ -31,26 +38,39 @@ namespace media {
 
 namespace {
 
+const int kNumChannels = 2;
+const int kBitsPerSample = 32;
+const int kDefaultFramesPerBuffer = 1024;
+const int kSilenceBufferFrames = 2048;
+const int kMaxOutputMs = 20;
+const int kMillisecondsPerSecond = 1000;
+
+const double kPlaybackRateEpsilon = 0.001;
+
 const CastAudioDecoder::OutputFormat kDecoderSampleFormat =
     CastAudioDecoder::kOutputPlanarFloat;
 
-const int64_t kInvalidDelayTimestamp = std::numeric_limits<int64_t>::min();
+const int64_t kInvalidTimestamp = std::numeric_limits<int64_t>::min();
 
-AudioDecoderAlsa::RenderingDelay kInvalidRenderingDelay() {
-  AudioDecoderAlsa::RenderingDelay delay;
-  delay.timestamp_microseconds = kInvalidDelayTimestamp;
-  delay.delay_microseconds = 0;
-  return delay;
-}
+const int64_t kNoPendingOutput = -1;
 
 }  // namespace
 
+AudioDecoderAlsa::RateShifterInfo::RateShifterInfo(float playback_rate)
+    : rate(playback_rate), input_frames(0), output_frames(0) {}
+
 AudioDecoderAlsa::AudioDecoderAlsa(MediaPipelineBackendAlsa* backend)
     : backend_(backend),
       task_runner_(backend->GetTaskRunner()),
       delegate_(nullptr),
-      is_eos_(false),
-      error_(false),
+      pending_buffer_complete_(false),
+      got_eos_(false),
+      pushed_eos_(false),
+      mixer_error_(false),
+      rate_shifter_output_(
+          ::media::AudioBus::Create(kNumChannels, kDefaultFramesPerBuffer)),
+      current_pts_(kInvalidTimestamp),
+      pending_output_frames_(kNoPendingOutput),
       volume_multiplier_(1.0f),
       weak_factory_(this) {
   TRACE_FUNCTION_ENTRY0();
@@ -74,11 +94,14 @@ void AudioDecoderAlsa::Initialize() {
   TRACE_FUNCTION_ENTRY0();
   DCHECK(delegate_);
   stats_ = Statistics();
-  is_eos_ = false;
-  last_buffer_pts_ = std::numeric_limits<int64_t>::min();
-
-  last_known_delay_.timestamp_microseconds = kInvalidDelayTimestamp;
-  last_known_delay_.delay_microseconds = 0;
+  pending_buffer_complete_ = false;
+  got_eos_ = false;
+  pushed_eos_ = false;
+  current_pts_ = kInvalidTimestamp;
+  pending_output_frames_ = kNoPendingOutput;
+
+  last_mixer_delay_.timestamp_microseconds = kInvalidTimestamp;
+  last_mixer_delay_.delay_microseconds = 0;
 }
 
 bool AudioDecoderAlsa::Start(int64_t start_pts) {
@@ -90,8 +113,12 @@ bool AudioDecoderAlsa::Start(int64_t start_pts) {
   mixer_input_->SetVolumeMultiplier(volume_multiplier_);
   // Create decoder_ if necessary. This can happen if Stop() was called, and
   // SetConfig() was not called since then.
-  if (!decoder_)
+  if (!decoder_) {
     CreateDecoder();
+  }
+  if (!rate_shifter_) {
+    CreateRateShifter(config_.samples_per_second);
+  }
   return true;
 }
 
@@ -99,6 +126,8 @@ void AudioDecoderAlsa::Stop() {
   TRACE_FUNCTION_ENTRY0();
   decoder_.reset();
   mixer_input_.reset();
+  rate_shifter_.reset();
+  weak_factory_.InvalidateWeakPtrs();
 
   Initialize();
 }
@@ -117,20 +146,35 @@ bool AudioDecoderAlsa::Resume() {
   return true;
 }
 
+bool AudioDecoderAlsa::SetPlaybackRate(float rate) {
+  if (std::abs(rate - 1.0) < kPlaybackRateEpsilon) {
+    // AudioRendererAlgorithm treats values close to 1 as exactly 1.
+    rate = 1.0f;
+  }
+  LOG(INFO) << "SetPlaybackRate to " << rate;
+
+  while (!rate_shifter_info_.empty() &&
+         rate_shifter_info_.back().input_frames == 0) {
+    rate_shifter_info_.pop_back();
+  }
+  rate_shifter_info_.push_back(RateShifterInfo(rate));
+  return true;
+}
+
 AudioDecoderAlsa::BufferStatus AudioDecoderAlsa::PushBuffer(
     CastDecoderBuffer* buffer) {
   TRACE_FUNCTION_ENTRY0();
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(buffer);
-  DCHECK(!is_eos_);
-  DCHECK(!error_);
+  DCHECK(!got_eos_);
+  DCHECK(!mixer_error_);
+  DCHECK(!pending_buffer_complete_);
 
   uint64_t input_bytes = buffer->end_of_stream() ? 0 : buffer->data_size();
   scoped_refptr<DecoderBufferBase> buffer_base(
       static_cast<DecoderBufferBase*>(buffer));
   if (!buffer->end_of_stream()) {
-    last_buffer_pts_ = buffer->timestamp();
-    current_pts_ = std::min(current_pts_, last_buffer_pts_);
+    current_pts_ = buffer->timestamp();
   }
 
   // If the buffer is already decoded, do not attempt to decode. Call
@@ -174,6 +218,11 @@ bool AudioDecoderAlsa::SetConfig(const AudioConfig& config) {
     return false;
   }
 
+  if (!rate_shifter_ ||
+      config.samples_per_second != config_.samples_per_second) {
+    CreateRateShifter(config.samples_per_second);
+  }
+
   if (mixer_input_ && config.samples_per_second != config_.samples_per_second) {
     // Destroy the old input first to ensure that the mixer output sample rate
     // is updated.
@@ -181,11 +230,17 @@ bool AudioDecoderAlsa::SetConfig(const AudioConfig& config) {
     mixer_input_.reset(new StreamMixerAlsaInput(
         this, config.samples_per_second, backend_->Primary()));
     mixer_input_->SetVolumeMultiplier(volume_multiplier_);
+    pending_output_frames_ = kNoPendingOutput;
   }
 
   config_ = config;
   decoder_.reset();
   CreateDecoder();
+
+  if (pending_buffer_complete_ && !rate_shifter_->IsQueueFull()) {
+    pending_buffer_complete_ = false;
+    delegate_->OnPushBufferComplete(MediaPipelineBackendAlsa::kBufferSuccess);
+  }
   return true;
 }
 
@@ -208,6 +263,17 @@ void AudioDecoderAlsa::CreateDecoder() {
                  weak_factory_.GetWeakPtr()));
 }
 
+void AudioDecoderAlsa::CreateRateShifter(int samples_per_second) {
+  rate_shifter_info_.clear();
+  rate_shifter_info_.push_back(RateShifterInfo(1.0f));
+
+  rate_shifter_.reset(new ::media::AudioRendererAlgorithm());
+  rate_shifter_->Initialize(::media::AudioParameters(
+      ::media::AudioParameters::AUDIO_PCM_LINEAR,
+      ::media::CHANNEL_LAYOUT_STEREO, samples_per_second, kBitsPerSample,
+      kDefaultFramesPerBuffer));
+}
+
 bool AudioDecoderAlsa::SetVolume(float multiplier) {
   TRACE_FUNCTION_ENTRY1(multiplier);
   DCHECK(task_runner_->BelongsToCurrentThread());
@@ -219,7 +285,24 @@ bool AudioDecoderAlsa::SetVolume(float multiplier) {
 
 AudioDecoderAlsa::RenderingDelay AudioDecoderAlsa::GetRenderingDelay() {
   TRACE_FUNCTION_ENTRY0();
-  return last_known_delay_;
+  AudioDecoderAlsa::RenderingDelay delay = last_mixer_delay_;
+  if (delay.timestamp_microseconds != kInvalidTimestamp) {
+    double usec_per_sample = 1000000.0 / config_.samples_per_second;
+
+    // Account for data that has been queued in the rate shifters.
+    for (const RateShifterInfo& info : rate_shifter_info_) {
+      double queued_output_frames =
+          (info.input_frames / info.rate) - info.output_frames;
+      delay.delay_microseconds += queued_output_frames * usec_per_sample;
+    }
+
+    // Account for data that is in the process of being pushed to the mixer.
+    if (pending_output_frames_ != kNoPendingOutput) {
+      delay.delay_microseconds += pending_output_frames_ * usec_per_sample;
+    }
+  }
+
+  return delay;
 }
 
 void AudioDecoderAlsa::OnDecoderInitialized(bool success) {
@@ -237,29 +320,161 @@ void AudioDecoderAlsa::OnBufferDecoded(
     const scoped_refptr<DecoderBufferBase>& decoded) {
   TRACE_FUNCTION_ENTRY0();
   DCHECK(task_runner_->BelongsToCurrentThread());
-  DCHECK(!is_eos_);
-
-  Statistics delta = Statistics();
+  DCHECK(!got_eos_);
+  DCHECK(!pending_buffer_complete_);
+  DCHECK(rate_shifter_);
 
   if (status == CastAudioDecoder::Status::kDecodeError) {
     LOG(ERROR) << "Decode error";
-    task_runner_->PostTask(FROM_HERE,
-                           base::Bind(&AudioDecoderAlsa::OnWritePcmCompletion,
-                                      weak_factory_.GetWeakPtr(),
-                                      MediaPipelineBackendAlsa::kBufferFailed,
-                                      kInvalidRenderingDelay()));
-    UpdateStatistics(delta);
+    delegate_->OnPushBufferComplete(MediaPipelineBackendAlsa::kBufferFailed);
+    return;
+  }
+  if (mixer_error_) {
+    delegate_->OnPushBufferComplete(MediaPipelineBackendAlsa::kBufferFailed);
     return;
   }
 
+  Statistics delta;
   delta.decoded_bytes = input_bytes;
   UpdateStatistics(delta);
 
-  if (decoded->end_of_stream())
-    is_eos_ = true;
+  if (decoded->end_of_stream()) {
+    got_eos_ = true;
+  } else {
+    int input_frames = decoded->data_size() / (kNumChannels * sizeof(float));
+
+    DCHECK(!rate_shifter_info_.empty());
+    RateShifterInfo* rate_info = &rate_shifter_info_.front();
+    // Bypass rate shifter if the rate is 1.0, and there are no frames queued
+    // in the rate shifter.
+    if (rate_info->rate == 1.0 && rate_shifter_->frames_buffered() == 0 &&
+        pending_output_frames_ == kNoPendingOutput) {
+      DCHECK_EQ(rate_info->output_frames, rate_info->input_frames);
+      pending_buffer_complete_ = true;
+      pending_output_frames_ = input_frames;
+      if (got_eos_) {
+        DCHECK(!pushed_eos_);
+        pushed_eos_ = true;
+      }
+      mixer_input_->WritePcm(decoded);
+      return;
+    }
+
+    // Otherwise, queue data into the rate shifter, and then try to push the
+    // rate-shifted data.
+    const uint8_t* channels[kNumChannels] = {
+        decoded->data(), decoded->data() + input_frames * sizeof(float)};
+    scoped_refptr<::media::AudioBuffer> buffer = ::media::AudioBuffer::CopyFrom(
+        ::media::kSampleFormatPlanarF32, ::media::CHANNEL_LAYOUT_STEREO,
+        kNumChannels, config_.samples_per_second, input_frames, channels,
+        base::TimeDelta());
+    rate_shifter_->EnqueueBuffer(buffer);
+    rate_shifter_info_.back().input_frames += input_frames;
+  }
 
+  PushRateShifted();
+  DCHECK(!rate_shifter_info_.empty());
+  // Can't check got_eos_ here, since it may have already been reset by a call
+  // to Stop().
+  if (decoded->end_of_stream() || (!rate_shifter_->IsQueueFull() &&
+                                   rate_shifter_info_.front().rate != 1.0)) {
+    delegate_->OnPushBufferComplete(MediaPipelineBackendAlsa::kBufferSuccess);
+  } else {
+    pending_buffer_complete_ = true;
+  }
+}
+
+void AudioDecoderAlsa::PushRateShifted() {
   DCHECK(mixer_input_);
-  mixer_input_->WritePcm(decoded);
+
+  if (pending_output_frames_ != kNoPendingOutput) {
+    return;
+  }
+
+  if (got_eos_) {
+    // Push some silence into the rate shifter so we can get out any remaining
+    // rate-shifted data.
+    rate_shifter_->EnqueueBuffer(::media::AudioBuffer::CreateEmptyBuffer(
+        ::media::CHANNEL_LAYOUT_STEREO, kNumChannels,
+        config_.samples_per_second, kSilenceBufferFrames, base::TimeDelta()));
+  }
+
+  DCHECK(!rate_shifter_info_.empty());
+  RateShifterInfo* rate_info = &rate_shifter_info_.front();
+  int64_t possible_output_frames = rate_info->input_frames / rate_info->rate;
+  DCHECK_GE(possible_output_frames, rate_info->output_frames);
+
+  int desired_output_frames = possible_output_frames - rate_info->output_frames;
+  if (desired_output_frames == 0) {
+    if (got_eos_) {
+      DCHECK(!pushed_eos_);
+      pending_output_frames_ = 0;
+      pushed_eos_ = true;
+
+      scoped_refptr<DecoderBufferBase> eos_buffer(
+          new DecoderBufferAdapter(::media::DecoderBuffer::CreateEOSBuffer()));
+      mixer_input_->WritePcm(eos_buffer);
+    }
+    return;
+  }
+  // Don't push too many frames at a time.
+  desired_output_frames = std::min(
+      desired_output_frames,
+      config_.samples_per_second * kMaxOutputMs / kMillisecondsPerSecond);
+
+  if (desired_output_frames > rate_shifter_output_->frames()) {
+    rate_shifter_output_ =
+        ::media::AudioBus::Create(kNumChannels, desired_output_frames);
+  }
+
+  int out_frames = rate_shifter_->FillBuffer(
+      rate_shifter_output_.get(), 0, desired_output_frames, rate_info->rate);
+  if (out_frames <= 0) {
+    return;
+  }
+
+  rate_info->output_frames += out_frames;
+  DCHECK_GE(possible_output_frames, rate_info->output_frames);
+
+  int channel_data_size = out_frames * sizeof(float);
+  scoped_refptr<DecoderBufferBase> output_buffer(new DecoderBufferAdapter(
+      new ::media::DecoderBuffer(channel_data_size * kNumChannels)));
+  for (int c = 0; c < kNumChannels; ++c) {
+    memcpy(output_buffer->writable_data() + c * channel_data_size,
+           rate_shifter_output_->channel(c), channel_data_size);
+  }
+  pending_output_frames_ = out_frames;
+  mixer_input_->WritePcm(output_buffer);
+
+  if (rate_shifter_info_.size() > 1 &&
+      possible_output_frames == rate_info->output_frames) {
+    double remaining_input_frames =
+        rate_info->input_frames - (rate_info->output_frames * rate_info->rate);
+    rate_shifter_info_.pop_front();
+
+    rate_info = &rate_shifter_info_.front();
+    LOG(INFO) << "New playback rate in effect: " << rate_info->rate;
+    rate_info->input_frames += remaining_input_frames;
+    DCHECK_EQ(0, rate_info->output_frames);
+
+    // If new playback rate is 1.0, clear out 'extra' data in the rate shifter.
+    // When doing rate shifting, the rate shifter queue holds data after it has
+    // been logically played; once we switch to passthrough mode (rate == 1.0),
+    // that old data needs to be cleared out.
+    if (rate_info->rate == 1.0) {
+      int extra_frames = rate_shifter_->frames_buffered() -
+                         static_cast<int>(rate_info->input_frames);
+      if (extra_frames > 0) {
+        // Clear out extra buffered data.
+        std::unique_ptr<::media::AudioBus> dropped =
+            ::media::AudioBus::Create(kNumChannels, extra_frames);
+        int cleared_frames =
+            rate_shifter_->FillBuffer(dropped.get(), 0, extra_frames, 1.0f);
+        DCHECK_EQ(extra_frames, cleared_frames);
+      }
+      rate_info->input_frames = rate_shifter_->frames_buffered();
+    }
+  }
 }
 
 bool AudioDecoderAlsa::BypassDecoder() const {
@@ -273,13 +488,34 @@ void AudioDecoderAlsa::OnWritePcmCompletion(BufferStatus status,
                                             const RenderingDelay& delay) {
   TRACE_FUNCTION_ENTRY0();
   DCHECK(task_runner_->BelongsToCurrentThread());
-  if (status == MediaPipelineBackendAlsa::kBufferSuccess && !is_eos_)
-    current_pts_ = last_buffer_pts_;
-  if (delay.timestamp_microseconds != kInvalidDelayTimestamp)
-    last_known_delay_ = delay;
-  delegate_->OnPushBufferComplete(status);
-  if (is_eos_)
+  DCHECK_EQ(MediaPipelineBackendAlsa::kBufferSuccess, status);
+  pending_output_frames_ = kNoPendingOutput;
+  last_mixer_delay_ = delay;
+
+  if (pushed_eos_) {
+    if (pending_buffer_complete_) {
+      pending_buffer_complete_ = false;
+      delegate_->OnPushBufferComplete(MediaPipelineBackendAlsa::kBufferSuccess);
+    }
     delegate_->OnEndOfStream();
+  } else {
+    task_runner_->PostTask(FROM_HERE, base::Bind(&AudioDecoderAlsa::PushMorePcm,
+                                                 weak_factory_.GetWeakPtr()));
+  }
+}
+
+void AudioDecoderAlsa::PushMorePcm() {
+  PushRateShifted();
+
+  DCHECK(!rate_shifter_info_.empty());
+  if (pending_buffer_complete_) {
+    double rate = rate_shifter_info_.front().rate;
+    if ((rate == 1.0 && pending_output_frames_ == kNoPendingOutput) ||
+        (rate != 1.0 && !rate_shifter_->IsQueueFull())) {
+      pending_buffer_complete_ = false;
+      delegate_->OnPushBufferComplete(MediaPipelineBackendAlsa::kBufferSuccess);
+    }
+  }
 }
 
 void AudioDecoderAlsa::OnMixerError(MixerError error) {
@@ -287,7 +523,7 @@ void AudioDecoderAlsa::OnMixerError(MixerError error) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   if (error != MixerError::kInputIgnored)
     LOG(ERROR) << "Mixer error occurred.";
-  error_ = true;
+  mixer_error_ = true;
   delegate_->OnDecoderError();
 }