starboard/android/shared/audio_renderer_passthrough.cc - cobalt - Git at Google

 // Copyright 2021 The Cobalt Authors. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 #include "starboard/android/shared/audio_renderer_passthrough.h"

 #include <algorithm>
 #include <utility>

 #include "starboard/android/shared/audio_decoder_passthrough.h"
 #include "starboard/android/shared/jni_env_ext.h"
 #include "starboard/android/shared/jni_utils.h"
 #include "starboard/common/string.h"
 #include "starboard/memory.h"

 namespace starboard {
 namespace android {
 namespace shared {
 namespace {

 // Soft limit to ensure that the user of AudioRendererPassthrough won't keep
 // pushing data when there are enough decoded audio buffers.
 constexpr int kMaxDecodedAudios = 64;

 constexpr SbTime kAudioTrackUpdateInternal = kSbTimeMillisecond * 5;

 constexpr int kPreferredBufferSizeInBytes = 16 * 1024;
 // TODO: Enable passthrough with tunnel mode.
 constexpr int kTunnelModeAudioSessionId = -1;

 // C++ rewrite of ExoPlayer function parseAc3SyncframeAudioSampleCount(), it
 // works for AC-3, E-AC-3, and E-AC-3-JOC.
 // The ExoPlayer implementation is based on
 // https://www.etsi.org/deliver/etsi_ts/102300_102399/102366/01.04.01_60/ts_102366v010401p.pdf.
 int ParseAc3SyncframeAudioSampleCount(const uint8_t* buffer, int size) {
   SB_DCHECK(buffer);

   constexpr int kAudioSamplesPerAudioBlock = 256;
   // Each syncframe has 6 blocks that provide 256 new audio samples. See
   // subsection 4.1.
   constexpr int kAc3SyncFrameAudioSampleCount = 6 * kAudioSamplesPerAudioBlock;
   // Number of audio blocks per E-AC-3 syncframe, indexed by numblkscod.
   constexpr int kBlocksPerSyncFrameByNumblkscod[] = {1, 2, 3, 6};

   if (size < 6) {
     SB_LOG(WARNING) << "Invalid e/ac3 input buffer size " << size;
     return kAc3SyncFrameAudioSampleCount;
   }

   // Parse the bitstream ID for AC-3 and E-AC-3 (see subsections 4.3, E.1.2 and
   // E.1.3.1.6).
   const bool is_eac3 = ((buffer[5] & 0xF8) >> 3) > 10;
   if (is_eac3) {
     int fscod = (buffer[4] & 0xC0) >> 6;
     int numblkscod = fscod == 0x03 ? 3 : (buffer[4] & 0x30) >> 4;
     return kBlocksPerSyncFrameByNumblkscod[numblkscod] *
            kAudioSamplesPerAudioBlock;
   } else {
     return kAc3SyncFrameAudioSampleCount;
   }
 }

 }  // namespace

 AudioRendererPassthrough::AudioRendererPassthrough(
     const SbMediaAudioSampleInfo& audio_sample_info,
     SbDrmSystem drm_system,
     bool enable_audio_device_callback)
     : audio_sample_info_(audio_sample_info),
       enable_audio_device_callback_(enable_audio_device_callback) {
   SB_DCHECK(audio_sample_info_.codec == kSbMediaAudioCodecAc3 ||
             audio_sample_info_.codec == kSbMediaAudioCodecEac3);
   if (SbDrmSystemIsValid(drm_system)) {
     SB_LOG(INFO) << "Creating AudioDecoder as decryptor.";
     scoped_ptr<AudioDecoder> audio_decoder(new AudioDecoder(
         audio_sample_info_.codec, audio_sample_info, drm_system));
     if (audio_decoder->is_valid()) {
       decoder_.reset(audio_decoder.release());
     }
   } else {
     SB_LOG(INFO) << "Creating AudioDecoderPassthrough.";
     decoder_.reset(
         new AudioDecoderPassthrough(audio_sample_info_.samples_per_second));
   }
 }

 AudioRendererPassthrough::~AudioRendererPassthrough() {
   SB_DCHECK(BelongsToCurrentThread());

   if (is_valid()) {
     SB_LOG(INFO) << "Force a seek to 0 to reset all states before destructing.";
     Seek(0);
   }
 }

 void AudioRendererPassthrough::Initialize(const ErrorCB& error_cb,
                                           const PrerolledCB& prerolled_cb,
                                           const EndedCB& ended_cb) {
   SB_DCHECK(BelongsToCurrentThread());
   SB_DCHECK(error_cb);
   SB_DCHECK(prerolled_cb);
   SB_DCHECK(ended_cb);
   SB_DCHECK(!error_cb_);
   SB_DCHECK(!prerolled_cb_);
   SB_DCHECK(!ended_cb_);
   SB_DCHECK(decoder_);

   error_cb_ = error_cb;
   prerolled_cb_ = prerolled_cb;
   ended_cb_ = ended_cb;

   decoder_->Initialize(
       std::bind(&AudioRendererPassthrough::OnDecoderOutput, this), error_cb);
 }

 void AudioRendererPassthrough::WriteSample(
     const scoped_refptr<InputBuffer>& input_buffer) {
   SB_DCHECK(BelongsToCurrentThread());
   SB_DCHECK(input_buffer);
   SB_DCHECK(can_accept_more_data_.load());

   if (!audio_track_thread_) {
     audio_track_thread_.reset(
         new JobThread("AudioPassthrough", 0, kSbThreadPriorityHigh));
     audio_track_thread_->Schedule(std::bind(
         &AudioRendererPassthrough::CreateAudioTrackAndStartProcessing, this));
   }

   if (frames_per_input_buffer_ == 0) {
     frames_per_input_buffer_ = ParseAc3SyncframeAudioSampleCount(
         input_buffer->data(), input_buffer->size());
     SB_LOG(INFO) << "Got frames per input buffer " << frames_per_input_buffer_;
   }

   can_accept_more_data_.store(false);

   decoder_->Decode(
       input_buffer,
       std::bind(&AudioRendererPassthrough::OnDecoderConsumed, this));
 }

 void AudioRendererPassthrough::WriteEndOfStream() {
   SB_DCHECK(BelongsToCurrentThread());

   if (end_of_stream_written_) {
     SB_LOG(INFO) << "WriteEndOfStream() ignored as |end_of_stream_written_| is"
                  << " true.";
     return;
   }

   SB_LOG(INFO) << "WriteEndOfStream() called.";

   end_of_stream_written_ = true;

   if (audio_track_thread_) {
     decoder_->WriteEndOfStream();
     return;
   }

   SB_LOG(INFO) << "Audio eos reached without any samples written.";
   end_of_stream_played_.store(true);
   ended_cb_();
 }

 void AudioRendererPassthrough::SetVolume(double volume) {
   SB_DCHECK(BelongsToCurrentThread());

   if (volume_ == volume) {
     SB_LOG(INFO) << "Volume already at " << volume;
     return;
   }

   SB_LOG(INFO) << "Set volume to " << volume;

   ScopedLock scoped_lock(mutex_);
   volume_ = volume;
 }

 bool AudioRendererPassthrough::IsEndOfStreamWritten() const {
   SB_DCHECK(BelongsToCurrentThread());

   return end_of_stream_written_;
 }

 bool AudioRendererPassthrough::IsEndOfStreamPlayed() const {
   SB_DCHECK(BelongsToCurrentThread());

   return end_of_stream_played_.load();
 }

 bool AudioRendererPassthrough::CanAcceptMoreData() const {
   SB_DCHECK(BelongsToCurrentThread());

   ScopedLock scoped_lock(mutex_);
   return can_accept_more_data_.load() &&
          decoded_audios_.size() < kMaxDecodedAudios;
 }

 void AudioRendererPassthrough::Play() {
   SB_DCHECK(BelongsToCurrentThread());

   if (!paused_) {
     SB_LOG(INFO) << "Already playing.";
     return;
   }

   SB_LOG(INFO) << "Play.";

   ScopedLock scoped_lock(mutex_);
   paused_ = false;
 }

 void AudioRendererPassthrough::Pause() {
   SB_DCHECK(BelongsToCurrentThread());

   if (paused_) {
     SB_LOG(INFO) << "Already paused.";
     return;
   }

   SB_LOG(INFO) << "Pause.";

   ScopedLock scoped_lock(mutex_);
   paused_ = true;
 }

 void AudioRendererPassthrough::SetPlaybackRate(double playback_rate) {
   SB_DCHECK(BelongsToCurrentThread());

   if (playback_rate > 0.0 && playback_rate != 1.0) {
     // TODO: Report unsupported playback rate as an error.
     SB_LOG(WARNING) << "Playback rate " << playback_rate << " is not supported"
                     << " and is set to 1.0.";
     playback_rate = 1.0;
   }

   if (playback_rate_ == playback_rate) {
     SB_LOG(INFO) << "Playback rate already at " << playback_rate;
     return;
   }

   SB_LOG(INFO) << "Change playback rate from " << playback_rate_ << " to "
                << playback_rate << ".";

   ScopedLock scoped_lock(mutex_);
   playback_rate_ = playback_rate;
 }

 void AudioRendererPassthrough::Seek(SbTime seek_to_time) {
   SB_DCHECK(BelongsToCurrentThread());

   SB_LOG(INFO) << "Seek to " << seek_to_time;

   decoder_->Reset();

   bool seek_to_time_set = false;
   if (audio_track_thread_) {
     audio_track_thread_->ScheduleAndWait(
         std::bind(&AudioRendererPassthrough::FlushAudioTrackAndStopProcessing,
                   this, seek_to_time));
     // |seek_to_time_| is updated inside FlushAudioTrackAndStopProcessing(),
     // update the flag so we needn't set it again below.
     seek_to_time_set = true;
     // Destroy the audio track thread, it will be re-created during preroll.
     audio_track_thread_.reset();
   }

   CancelPendingJobs();

   ScopedLock scoped_lock(mutex_);

   can_accept_more_data_.store(true);
   prerolled_.store(false);
   end_of_stream_played_.store(false);
   total_frames_written_ = 0;

   end_of_stream_written_ = false;

   stop_called_ = false;
   playback_head_position_when_stopped_ = 0;
   stopped_at_ = 0;
   if (!seek_to_time_set) {
     seek_to_time_ = seek_to_time;
   }
   paused_ = true;
   decoded_audios_ = std::queue<scoped_refptr<DecodedAudio>>();  // clear it
   decoded_audio_writing_in_progress_ = nullptr;
   decoded_audio_writing_offset_ = 0;
   total_frames_written_on_audio_track_thread_ = 0;
 }

 // This function can be called from *any* threads.
 SbTime AudioRendererPassthrough::GetCurrentMediaTime(bool* is_playing,
                                                      bool* is_eos_played,
                                                      bool* is_underflow,
                                                      double* playback_rate) {
   SB_DCHECK(is_playing);
   SB_DCHECK(is_eos_played);
   SB_DCHECK(is_underflow);
   SB_DCHECK(playback_rate);

   ScopedLock scoped_lock(mutex_);
   *is_playing = !paused_;
   *is_eos_played = end_of_stream_played_.load();
   *is_underflow = false;  // TODO: Support underflow
   *playback_rate = playback_rate_;

   if (!audio_track_bridge_) {
     return seek_to_time_;
   }

   if (stop_called_) {
     // When AudioTrackBridge::Stop() is called, the playback will continue until
     // all the frames written are played, as the AudioTrack in created in
     // MODE_STREAM.
     auto now = SbTimeGetMonotonicNow();
     SB_DCHECK(now >= stopped_at_);
     auto time_elapsed = now - stopped_at_;
     int64_t frames_played =
         time_elapsed * audio_sample_info_.samples_per_second / kSbTimeSecond;
     int64_t total_frames_played =
         frames_played + playback_head_position_when_stopped_;
     total_frames_played = std::min(total_frames_played, total_frames_written_);
     return seek_to_time_ + total_frames_played * kSbTimeSecond /
                                audio_sample_info_.samples_per_second;
   }

   SbTime updated_at;
   auto playback_head_position =
       audio_track_bridge_->GetAudioTimestamp(&updated_at);
   if (playback_head_position <= 0) {
     // The playback is warming up, don't adjust the media time by the monotonic
     // system time.
     return seek_to_time_;
   }

   // TODO: This may cause time regression, because the unadjusted time will be
   //       returned on pause, after an adjusted time has been returned.
   SbTime playback_time =
       seek_to_time_ + playback_head_position * kSbTimeSecond /
                           audio_sample_info_.samples_per_second;
   if (paused_ || playback_rate_ == 0.0) {
     return playback_time;
   }

   // TODO: Cap this to the maximum frames written to the AudioTrack.
   auto now = SbTimeGetMonotonicNow();
   SB_LOG_IF(WARNING, now < updated_at)
       << "now (" << now << ") is not greater than updated_at (" << updated_at
       << ").";
   playback_time += std::max<SbTime>(now - updated_at, 0);

   return playback_time;
 }

 void AudioRendererPassthrough::CreateAudioTrackAndStartProcessing() {
   SB_DCHECK(audio_track_thread_);
   SB_DCHECK(audio_track_thread_->BelongsToCurrentThread());
   SB_DCHECK(error_cb_);

   if (audio_track_bridge_) {
     SB_DCHECK(!update_status_and_write_data_token_.is_valid());
     AudioTrackState initial_state;
     update_status_and_write_data_token_ = audio_track_thread_->Schedule(
         std::bind(&AudioRendererPassthrough::UpdateStatusAndWriteData, this,
                   initial_state));
     SB_LOG(INFO) << "|audio_track_bridge_| already created, start processing.";
     return;
   }

   std::unique_ptr<AudioTrackBridge> audio_track_bridge(new AudioTrackBridge(
       audio_sample_info_.codec == kSbMediaAudioCodecAc3
           ? kSbMediaAudioCodingTypeAc3
           : kSbMediaAudioCodingTypeDolbyDigitalPlus,
       optional<SbMediaAudioSampleType>(),  // Not required in passthrough mode
       audio_sample_info_.number_of_channels,
       audio_sample_info_.samples_per_second, kPreferredBufferSizeInBytes,
       enable_audio_device_callback_, false /* enable_pcm_content_type_movie */,
       kTunnelModeAudioSessionId, false /* is_web_audio */));

   if (!audio_track_bridge->is_valid()) {
     error_cb_(kSbPlayerErrorDecode, "Error creating AudioTrackBridge");
     return;
   }

   {
     ScopedLock scoped_lock(mutex_);
     audio_track_bridge_ = std::move(audio_track_bridge);
   }

   AudioTrackState initial_state;
   update_status_and_write_data_token_ = audio_track_thread_->Schedule(
       std::bind(&AudioRendererPassthrough::UpdateStatusAndWriteData, this,
                 initial_state));
   SB_LOG(INFO) << "|audio_track_bridge_| created, start processing.";
 }

 void AudioRendererPassthrough::FlushAudioTrackAndStopProcessing(
     SbTime seek_to_time) {
   SB_DCHECK(audio_track_thread_);
   SB_DCHECK(audio_track_thread_->BelongsToCurrentThread());

   SB_LOG(INFO) << "Pause audio track and stop processing.";

   // Flushing of |audio_track_bridge_| and updating of |seek_to_time_| have to
   // be done together under lock to avoid |seek_to_time_| being added to a stale
   // playback head or vice versa in GetCurrentMediaTime().
   ScopedLock scoped_lock(mutex_);

   // We have to reuse |audio_track_bridge_| instead of creating a new one, to
   // reduce output mode switching between PCM and e/ac3.  Otherwise a noticeable
   // silence can be observed after seeking on some audio receivers.
   // TODO: Consider reusing audio sink for non-passthrough playbacks, to see if
   //       it reduces latency after seeking.
   audio_track_bridge_->PauseAndFlush();
   seek_to_time_ = seek_to_time;
   paused_ = true;
   if (update_status_and_write_data_token_.is_valid()) {
     audio_track_thread_->RemoveJobByToken(update_status_and_write_data_token_);
     update_status_and_write_data_token_.ResetToInvalid();
   }
 }

 void AudioRendererPassthrough::UpdateStatusAndWriteData(
     const AudioTrackState previous_state) {
   SB_DCHECK(audio_track_thread_);
   SB_DCHECK(audio_track_thread_->BelongsToCurrentThread());
   SB_DCHECK(error_cb_);
   SB_DCHECK(audio_track_bridge_);

   if (enable_audio_device_callback_ &&
       audio_track_bridge_->GetAndResetHasAudioDeviceChanged()) {
     SB_LOG(INFO) << "Audio device changed, raising a capability changed error "
                     "to restart playback.";
     error_cb_(kSbPlayerErrorCapabilityChanged,
               "Audio device capability changed");
     audio_track_bridge_->PauseAndFlush();
     return;
   }

   AudioTrackState current_state;

   {
     ScopedLock scoped_lock(mutex_);
     current_state.volume = volume_;
     current_state.paused = paused_;
     current_state.playback_rate = playback_rate_;

     if (!decoded_audio_writing_in_progress_ && !decoded_audios_.empty()) {
       decoded_audio_writing_in_progress_ = decoded_audios_.front();
       decoded_audios_.pop();
       decoded_audio_writing_offset_ = 0;
     }
   }

   if (previous_state.volume != current_state.volume) {
     audio_track_bridge_->SetVolume(current_state.volume);
   }
   if (previous_state.playing() != current_state.playing()) {
     if (current_state.playing()) {
       audio_track_bridge_->Play();
       SB_LOG(INFO) << "Played on AudioTrack thread.";
       ScopedLock scoped_lock(mutex_);
       stop_called_ = false;
     } else {
       audio_track_bridge_->Pause();
       SB_LOG(INFO) << "Paused on AudioTrack thread.";
     }
   }

   bool fully_written = false;
   if (decoded_audio_writing_in_progress_) {
     if (decoded_audio_writing_in_progress_->is_end_of_stream()) {
       if (!prerolled_.exchange(true)) {
         SB_LOG(INFO) << "Prerolled due to end of stream.";
         prerolled_cb_();
       }
       ScopedLock scoped_lock(mutex_);
       if (current_state.playing() && !stop_called_) {
         // TODO: Check if we can apply the same stop logic to non-passthrough.
         audio_track_bridge_->Stop();
         stop_called_ = true;
         playback_head_position_when_stopped_ =
             audio_track_bridge_->GetAudioTimestamp(&stopped_at_);
         total_frames_written_ = total_frames_written_on_audio_track_thread_;
         decoded_audio_writing_in_progress_ = nullptr;
         SB_LOG(INFO) << "Audio track stopped at " << stopped_at_
                      << ", playback head: "
                      << playback_head_position_when_stopped_;
       }
     } else {
       auto sample_buffer = decoded_audio_writing_in_progress_->buffer() +
                            decoded_audio_writing_offset_;
       auto samples_to_write = (decoded_audio_writing_in_progress_->size() -
                                decoded_audio_writing_offset_);
       // TODO: |sync_time| currently doesn't take partial writes into account.
       //       It is not used in non-tunneled mode so it doesn't matter, but we
       //       should revisit this.
       auto sync_time = decoded_audio_writing_in_progress_->timestamp();
       int samples_written = audio_track_bridge_->WriteSample(
           sample_buffer, samples_to_write, sync_time);
       // Error code returned as negative value, like kAudioTrackErrorDeadObject.
       if (samples_written < 0) {
         if (samples_written == AudioTrackBridge::kAudioTrackErrorDeadObject) {
           // Inform the audio end point change.
           SB_LOG(INFO)
               << "Write error for dead audio track, audio device capability "
                  "has likely changed. Restarting playback.";
           error_cb_(kSbPlayerErrorCapabilityChanged,
                     "Audio device capability changed");
           audio_track_bridge_->PauseAndFlush();
           return;
         }
         // `kSbPlayerErrorDecode` is used for general SbPlayer error, there is
         // no error code corresponding to audio sink.
         error_cb_(
             kSbPlayerErrorDecode,
             FormatString("Error while writing frames: %d", samples_written));
       }
       decoded_audio_writing_offset_ += samples_written;

       if (decoded_audio_writing_offset_ ==
           decoded_audio_writing_in_progress_->size()) {
         total_frames_written_on_audio_track_thread_ += frames_per_input_buffer_;
         decoded_audio_writing_in_progress_ = nullptr;
         decoded_audio_writing_offset_ = 0;
         fully_written = true;
       } else if (!prerolled_.exchange(true)) {
         // The audio sink no longer takes all the samples written to it.  Assume
         // that it has enough samples and preroll is finished.
         SB_LOG(INFO) << "Prerolled.";
         prerolled_cb_();
       }
     }
   }

   // EOS is handled on this thread instead of in GetCurrentMediaTime(), because
   // GetCurrentMediaTime() is not guaranteed to be called.
   if (stop_called_ && !end_of_stream_played_.load()) {
     auto time_elapsed = SbTimeGetMonotonicNow() - stopped_at_;
     auto frames_played =
         time_elapsed * audio_sample_info_.samples_per_second / kSbTimeSecond;
     if (frames_played + playback_head_position_when_stopped_ >=
         total_frames_written_on_audio_track_thread_) {
       end_of_stream_played_.store(true);
       ended_cb_();
       SB_LOG(INFO) << "Audio playback ended, UpdateStatusAndWriteData stopped.";
       return;
     }
   }

   update_status_and_write_data_token_ = audio_track_thread_->Schedule(
       std::bind(&AudioRendererPassthrough::UpdateStatusAndWriteData, this,
                 current_state),
       fully_written ? 0 : kAudioTrackUpdateInternal);
 }

 // This function can be called from *any* threads.
 void AudioRendererPassthrough::OnDecoderConsumed() {
   auto old_value = can_accept_more_data_.exchange(true);
   SB_DCHECK(!old_value);
 }

 // This function can be called from *any* threads.
 void AudioRendererPassthrough::OnDecoderOutput() {
   int decoded_audio_sample_rate;
   auto decoded_audio = decoder_->Read(&decoded_audio_sample_rate);
   SB_DCHECK(decoded_audio);

   ScopedLock scoped_lock(mutex_);
   decoded_audios_.push(decoded_audio);
 }

 }  // namespace shared
 }  // namespace android
 }  // namespace starboard
	// Copyright 2021 The Cobalt Authors. All Rights Reserved.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	#include "starboard/android/shared/audio_renderer_passthrough.h"

	#include <algorithm>
	#include <utility>

	#include "starboard/android/shared/audio_decoder_passthrough.h"
	#include "starboard/android/shared/jni_env_ext.h"
	#include "starboard/android/shared/jni_utils.h"
	#include "starboard/common/string.h"
	#include "starboard/memory.h"

	namespace starboard {
	namespace android {
	namespace shared {
	namespace {

	// Soft limit to ensure that the user of AudioRendererPassthrough won't keep
	// pushing data when there are enough decoded audio buffers.
	constexpr int kMaxDecodedAudios = 64;

	constexpr SbTime kAudioTrackUpdateInternal = kSbTimeMillisecond * 5;

	constexpr int kPreferredBufferSizeInBytes = 16 * 1024;
	// TODO: Enable passthrough with tunnel mode.
	constexpr int kTunnelModeAudioSessionId = -1;

	// C++ rewrite of ExoPlayer function parseAc3SyncframeAudioSampleCount(), it
	// works for AC-3, E-AC-3, and E-AC-3-JOC.
	// The ExoPlayer implementation is based on
	// https://www.etsi.org/deliver/etsi_ts/102300_102399/102366/01.04.01_60/ts_102366v010401p.pdf.
	int ParseAc3SyncframeAudioSampleCount(const uint8_t* buffer, int size) {
	SB_DCHECK(buffer);

	constexpr int kAudioSamplesPerAudioBlock = 256;
	// Each syncframe has 6 blocks that provide 256 new audio samples. See
	// subsection 4.1.
	constexpr int kAc3SyncFrameAudioSampleCount = 6 * kAudioSamplesPerAudioBlock;
	// Number of audio blocks per E-AC-3 syncframe, indexed by numblkscod.
	constexpr int kBlocksPerSyncFrameByNumblkscod[] = {1, 2, 3, 6};

	if (size < 6) {
	SB_LOG(WARNING) << "Invalid e/ac3 input buffer size " << size;
	return kAc3SyncFrameAudioSampleCount;
	}

	// Parse the bitstream ID for AC-3 and E-AC-3 (see subsections 4.3, E.1.2 and
	// E.1.3.1.6).
	const bool is_eac3 = ((buffer[5] & 0xF8) >> 3) > 10;
	if (is_eac3) {
	int fscod = (buffer[4] & 0xC0) >> 6;
	int numblkscod = fscod == 0x03 ? 3 : (buffer[4] & 0x30) >> 4;
	return kBlocksPerSyncFrameByNumblkscod[numblkscod] *
	kAudioSamplesPerAudioBlock;
	} else {
	return kAc3SyncFrameAudioSampleCount;
	}
	}

	} // namespace

	AudioRendererPassthrough::AudioRendererPassthrough(
	const SbMediaAudioSampleInfo& audio_sample_info,
	SbDrmSystem drm_system,
	bool enable_audio_device_callback)
	: audio_sample_info_(audio_sample_info),
	enable_audio_device_callback_(enable_audio_device_callback) {
	SB_DCHECK(audio_sample_info_.codec == kSbMediaAudioCodecAc3 \|\|
	audio_sample_info_.codec == kSbMediaAudioCodecEac3);
	if (SbDrmSystemIsValid(drm_system)) {
	SB_LOG(INFO) << "Creating AudioDecoder as decryptor.";
	scoped_ptr<AudioDecoder> audio_decoder(new AudioDecoder(
	audio_sample_info_.codec, audio_sample_info, drm_system));
	if (audio_decoder->is_valid()) {
	decoder_.reset(audio_decoder.release());
	}
	} else {
	SB_LOG(INFO) << "Creating AudioDecoderPassthrough.";
	decoder_.reset(
	new AudioDecoderPassthrough(audio_sample_info_.samples_per_second));
	}
	}

	AudioRendererPassthrough::~AudioRendererPassthrough() {
	SB_DCHECK(BelongsToCurrentThread());

	if (is_valid()) {
	SB_LOG(INFO) << "Force a seek to 0 to reset all states before destructing.";
	Seek(0);
	}
	}

	void AudioRendererPassthrough::Initialize(const ErrorCB& error_cb,
	const PrerolledCB& prerolled_cb,
	const EndedCB& ended_cb) {
	SB_DCHECK(BelongsToCurrentThread());
	SB_DCHECK(error_cb);
	SB_DCHECK(prerolled_cb);
	SB_DCHECK(ended_cb);
	SB_DCHECK(!error_cb_);
	SB_DCHECK(!prerolled_cb_);
	SB_DCHECK(!ended_cb_);
	SB_DCHECK(decoder_);

	error_cb_ = error_cb;
	prerolled_cb_ = prerolled_cb;
	ended_cb_ = ended_cb;

	decoder_->Initialize(
	std::bind(&AudioRendererPassthrough::OnDecoderOutput, this), error_cb);
	}

	void AudioRendererPassthrough::WriteSample(
	const scoped_refptr<InputBuffer>& input_buffer) {
	SB_DCHECK(BelongsToCurrentThread());
	SB_DCHECK(input_buffer);
	SB_DCHECK(can_accept_more_data_.load());

	if (!audio_track_thread_) {
	audio_track_thread_.reset(
	new JobThread("AudioPassthrough", 0, kSbThreadPriorityHigh));
	audio_track_thread_->Schedule(std::bind(
	&AudioRendererPassthrough::CreateAudioTrackAndStartProcessing, this));
	}

	if (frames_per_input_buffer_ == 0) {
	frames_per_input_buffer_ = ParseAc3SyncframeAudioSampleCount(
	input_buffer->data(), input_buffer->size());
	SB_LOG(INFO) << "Got frames per input buffer " << frames_per_input_buffer_;
	}

	can_accept_more_data_.store(false);

	decoder_->Decode(
	input_buffer,
	std::bind(&AudioRendererPassthrough::OnDecoderConsumed, this));
	}

	void AudioRendererPassthrough::WriteEndOfStream() {
	SB_DCHECK(BelongsToCurrentThread());

	if (end_of_stream_written_) {
	SB_LOG(INFO) << "WriteEndOfStream() ignored as \|end_of_stream_written_\| is"
	<< " true.";
	return;
	}

	SB_LOG(INFO) << "WriteEndOfStream() called.";

	end_of_stream_written_ = true;

	if (audio_track_thread_) {
	decoder_->WriteEndOfStream();
	return;
	}

	SB_LOG(INFO) << "Audio eos reached without any samples written.";
	end_of_stream_played_.store(true);
	ended_cb_();
	}

	void AudioRendererPassthrough::SetVolume(double volume) {
	SB_DCHECK(BelongsToCurrentThread());

	if (volume_ == volume) {
	SB_LOG(INFO) << "Volume already at " << volume;
	return;
	}

	SB_LOG(INFO) << "Set volume to " << volume;

	ScopedLock scoped_lock(mutex_);
	volume_ = volume;
	}

	bool AudioRendererPassthrough::IsEndOfStreamWritten() const {
	SB_DCHECK(BelongsToCurrentThread());

	return end_of_stream_written_;
	}

	bool AudioRendererPassthrough::IsEndOfStreamPlayed() const {
	SB_DCHECK(BelongsToCurrentThread());

	return end_of_stream_played_.load();
	}

	bool AudioRendererPassthrough::CanAcceptMoreData() const {
	SB_DCHECK(BelongsToCurrentThread());

	ScopedLock scoped_lock(mutex_);
	return can_accept_more_data_.load() &&
	decoded_audios_.size() < kMaxDecodedAudios;
	}

	void AudioRendererPassthrough::Play() {
	SB_DCHECK(BelongsToCurrentThread());

	if (!paused_) {
	SB_LOG(INFO) << "Already playing.";
	return;
	}

	SB_LOG(INFO) << "Play.";

	ScopedLock scoped_lock(mutex_);
	paused_ = false;
	}

	void AudioRendererPassthrough::Pause() {
	SB_DCHECK(BelongsToCurrentThread());

	if (paused_) {
	SB_LOG(INFO) << "Already paused.";
	return;
	}

	SB_LOG(INFO) << "Pause.";

	ScopedLock scoped_lock(mutex_);
	paused_ = true;
	}

	void AudioRendererPassthrough::SetPlaybackRate(double playback_rate) {
	SB_DCHECK(BelongsToCurrentThread());

	if (playback_rate > 0.0 && playback_rate != 1.0) {
	// TODO: Report unsupported playback rate as an error.
	SB_LOG(WARNING) << "Playback rate " << playback_rate << " is not supported"
	<< " and is set to 1.0.";
	playback_rate = 1.0;
	}

	if (playback_rate_ == playback_rate) {
	SB_LOG(INFO) << "Playback rate already at " << playback_rate;
	return;
	}

	SB_LOG(INFO) << "Change playback rate from " << playback_rate_ << " to "
	<< playback_rate << ".";

	ScopedLock scoped_lock(mutex_);
	playback_rate_ = playback_rate;
	}

	void AudioRendererPassthrough::Seek(SbTime seek_to_time) {
	SB_DCHECK(BelongsToCurrentThread());

	SB_LOG(INFO) << "Seek to " << seek_to_time;

	decoder_->Reset();

	bool seek_to_time_set = false;
	if (audio_track_thread_) {
	audio_track_thread_->ScheduleAndWait(
	std::bind(&AudioRendererPassthrough::FlushAudioTrackAndStopProcessing,
	this, seek_to_time));
	// \|seek_to_time_\| is updated inside FlushAudioTrackAndStopProcessing(),
	// update the flag so we needn't set it again below.
	seek_to_time_set = true;
	// Destroy the audio track thread, it will be re-created during preroll.
	audio_track_thread_.reset();
	}

	CancelPendingJobs();

	ScopedLock scoped_lock(mutex_);

	can_accept_more_data_.store(true);
	prerolled_.store(false);
	end_of_stream_played_.store(false);
	total_frames_written_ = 0;

	end_of_stream_written_ = false;

	stop_called_ = false;
	playback_head_position_when_stopped_ = 0;
	stopped_at_ = 0;
	if (!seek_to_time_set) {
	seek_to_time_ = seek_to_time;
	}
	paused_ = true;
	decoded_audios_ = std::queue<scoped_refptr<DecodedAudio>>(); // clear it
	decoded_audio_writing_in_progress_ = nullptr;
	decoded_audio_writing_offset_ = 0;
	total_frames_written_on_audio_track_thread_ = 0;
	}

	// This function can be called from any threads.
	SbTime AudioRendererPassthrough::GetCurrentMediaTime(bool* is_playing,
	bool* is_eos_played,
	bool* is_underflow,
	double* playback_rate) {
	SB_DCHECK(is_playing);
	SB_DCHECK(is_eos_played);
	SB_DCHECK(is_underflow);
	SB_DCHECK(playback_rate);

	ScopedLock scoped_lock(mutex_);
	*is_playing = !paused_;
	*is_eos_played = end_of_stream_played_.load();
	*is_underflow = false; // TODO: Support underflow
	*playback_rate = playback_rate_;

	if (!audio_track_bridge_) {
	return seek_to_time_;
	}

	if (stop_called_) {
	// When AudioTrackBridge::Stop() is called, the playback will continue until
	// all the frames written are played, as the AudioTrack in created in
	// MODE_STREAM.
	auto now = SbTimeGetMonotonicNow();
	SB_DCHECK(now >= stopped_at_);
	auto time_elapsed = now - stopped_at_;
	int64_t frames_played =
	time_elapsed * audio_sample_info_.samples_per_second / kSbTimeSecond;
	int64_t total_frames_played =
	frames_played + playback_head_position_when_stopped_;
	total_frames_played = std::min(total_frames_played, total_frames_written_);
	return seek_to_time_ + total_frames_played * kSbTimeSecond /
	audio_sample_info_.samples_per_second;
	}

	SbTime updated_at;
	auto playback_head_position =
	audio_track_bridge_->GetAudioTimestamp(&updated_at);
	if (playback_head_position <= 0) {
	// The playback is warming up, don't adjust the media time by the monotonic
	// system time.
	return seek_to_time_;
	}

	// TODO: This may cause time regression, because the unadjusted time will be
	// returned on pause, after an adjusted time has been returned.
	SbTime playback_time =
	seek_to_time_ + playback_head_position * kSbTimeSecond /
	audio_sample_info_.samples_per_second;
	if (paused_ \|\| playback_rate_ == 0.0) {
	return playback_time;
	}

	// TODO: Cap this to the maximum frames written to the AudioTrack.
	auto now = SbTimeGetMonotonicNow();
	SB_LOG_IF(WARNING, now < updated_at)
	<< "now (" << now << ") is not greater than updated_at (" << updated_at
	<< ").";
	playback_time += std::max<SbTime>(now - updated_at, 0);

	return playback_time;
	}

	void AudioRendererPassthrough::CreateAudioTrackAndStartProcessing() {
	SB_DCHECK(audio_track_thread_);
	SB_DCHECK(audio_track_thread_->BelongsToCurrentThread());
	SB_DCHECK(error_cb_);

	if (audio_track_bridge_) {
	SB_DCHECK(!update_status_and_write_data_token_.is_valid());
	AudioTrackState initial_state;
	update_status_and_write_data_token_ = audio_track_thread_->Schedule(
	std::bind(&AudioRendererPassthrough::UpdateStatusAndWriteData, this,
	initial_state));
	SB_LOG(INFO) << "\|audio_track_bridge_\| already created, start processing.";
	return;
	}

	std::unique_ptr<AudioTrackBridge> audio_track_bridge(new AudioTrackBridge(
	audio_sample_info_.codec == kSbMediaAudioCodecAc3
	? kSbMediaAudioCodingTypeAc3
	: kSbMediaAudioCodingTypeDolbyDigitalPlus,
	optional<SbMediaAudioSampleType>(), // Not required in passthrough mode
	audio_sample_info_.number_of_channels,
	audio_sample_info_.samples_per_second, kPreferredBufferSizeInBytes,
	enable_audio_device_callback_, false /* enable_pcm_content_type_movie */,
	kTunnelModeAudioSessionId, false /* is_web_audio */));

	if (!audio_track_bridge->is_valid()) {
	error_cb_(kSbPlayerErrorDecode, "Error creating AudioTrackBridge");
	return;
	}

	{
	ScopedLock scoped_lock(mutex_);
	audio_track_bridge_ = std::move(audio_track_bridge);
	}

	AudioTrackState initial_state;
	update_status_and_write_data_token_ = audio_track_thread_->Schedule(
	std::bind(&AudioRendererPassthrough::UpdateStatusAndWriteData, this,
	initial_state));
	SB_LOG(INFO) << "\|audio_track_bridge_\| created, start processing.";
	}

	void AudioRendererPassthrough::FlushAudioTrackAndStopProcessing(
	SbTime seek_to_time) {
	SB_DCHECK(audio_track_thread_);
	SB_DCHECK(audio_track_thread_->BelongsToCurrentThread());

	SB_LOG(INFO) << "Pause audio track and stop processing.";

	// Flushing of \|audio_track_bridge_\| and updating of \|seek_to_time_\| have to
	// be done together under lock to avoid \|seek_to_time_\| being added to a stale
	// playback head or vice versa in GetCurrentMediaTime().
	ScopedLock scoped_lock(mutex_);

	// We have to reuse \|audio_track_bridge_\| instead of creating a new one, to
	// reduce output mode switching between PCM and e/ac3. Otherwise a noticeable
	// silence can be observed after seeking on some audio receivers.
	// TODO: Consider reusing audio sink for non-passthrough playbacks, to see if
	// it reduces latency after seeking.
	audio_track_bridge_->PauseAndFlush();
	seek_to_time_ = seek_to_time;
	paused_ = true;
	if (update_status_and_write_data_token_.is_valid()) {
	audio_track_thread_->RemoveJobByToken(update_status_and_write_data_token_);
	update_status_and_write_data_token_.ResetToInvalid();
	}
	}

	void AudioRendererPassthrough::UpdateStatusAndWriteData(
	const AudioTrackState previous_state) {
	SB_DCHECK(audio_track_thread_);
	SB_DCHECK(audio_track_thread_->BelongsToCurrentThread());
	SB_DCHECK(error_cb_);
	SB_DCHECK(audio_track_bridge_);

	if (enable_audio_device_callback_ &&
	audio_track_bridge_->GetAndResetHasAudioDeviceChanged()) {
	SB_LOG(INFO) << "Audio device changed, raising a capability changed error "
	"to restart playback.";
	error_cb_(kSbPlayerErrorCapabilityChanged,
	"Audio device capability changed");
	audio_track_bridge_->PauseAndFlush();
	return;
	}

	AudioTrackState current_state;

	{
	ScopedLock scoped_lock(mutex_);
	current_state.volume = volume_;
	current_state.paused = paused_;
	current_state.playback_rate = playback_rate_;

	if (!decoded_audio_writing_in_progress_ && !decoded_audios_.empty()) {
	decoded_audio_writing_in_progress_ = decoded_audios_.front();
	decoded_audios_.pop();
	decoded_audio_writing_offset_ = 0;
	}
	}

	if (previous_state.volume != current_state.volume) {
	audio_track_bridge_->SetVolume(current_state.volume);
	}
	if (previous_state.playing() != current_state.playing()) {
	if (current_state.playing()) {
	audio_track_bridge_->Play();
	SB_LOG(INFO) << "Played on AudioTrack thread.";
	ScopedLock scoped_lock(mutex_);
	stop_called_ = false;
	} else {
	audio_track_bridge_->Pause();
	SB_LOG(INFO) << "Paused on AudioTrack thread.";
	}
	}

	bool fully_written = false;
	if (decoded_audio_writing_in_progress_) {
	if (decoded_audio_writing_in_progress_->is_end_of_stream()) {
	if (!prerolled_.exchange(true)) {
	SB_LOG(INFO) << "Prerolled due to end of stream.";
	prerolled_cb_();
	}
	ScopedLock scoped_lock(mutex_);
	if (current_state.playing() && !stop_called_) {
	// TODO: Check if we can apply the same stop logic to non-passthrough.
	audio_track_bridge_->Stop();
	stop_called_ = true;
	playback_head_position_when_stopped_ =
	audio_track_bridge_->GetAudioTimestamp(&stopped_at_);
	total_frames_written_ = total_frames_written_on_audio_track_thread_;
	decoded_audio_writing_in_progress_ = nullptr;
	SB_LOG(INFO) << "Audio track stopped at " << stopped_at_
	<< ", playback head: "
	<< playback_head_position_when_stopped_;
	}
	} else {
	auto sample_buffer = decoded_audio_writing_in_progress_->buffer() +
	decoded_audio_writing_offset_;
	auto samples_to_write = (decoded_audio_writing_in_progress_->size() -
	decoded_audio_writing_offset_);
	// TODO: \|sync_time\| currently doesn't take partial writes into account.
	// It is not used in non-tunneled mode so it doesn't matter, but we
	// should revisit this.
	auto sync_time = decoded_audio_writing_in_progress_->timestamp();
	int samples_written = audio_track_bridge_->WriteSample(
	sample_buffer, samples_to_write, sync_time);
	// Error code returned as negative value, like kAudioTrackErrorDeadObject.
	if (samples_written < 0) {
	if (samples_written == AudioTrackBridge::kAudioTrackErrorDeadObject) {
	// Inform the audio end point change.
	SB_LOG(INFO)
	<< "Write error for dead audio track, audio device capability "
	"has likely changed. Restarting playback.";
	error_cb_(kSbPlayerErrorCapabilityChanged,
	"Audio device capability changed");
	audio_track_bridge_->PauseAndFlush();
	return;
	}
	// `kSbPlayerErrorDecode` is used for general SbPlayer error, there is
	// no error code corresponding to audio sink.
	error_cb_(
	kSbPlayerErrorDecode,
	FormatString("Error while writing frames: %d", samples_written));
	}
	decoded_audio_writing_offset_ += samples_written;

	if (decoded_audio_writing_offset_ ==
	decoded_audio_writing_in_progress_->size()) {
	total_frames_written_on_audio_track_thread_ += frames_per_input_buffer_;
	decoded_audio_writing_in_progress_ = nullptr;
	decoded_audio_writing_offset_ = 0;
	fully_written = true;
	} else if (!prerolled_.exchange(true)) {
	// The audio sink no longer takes all the samples written to it. Assume
	// that it has enough samples and preroll is finished.
	SB_LOG(INFO) << "Prerolled.";
	prerolled_cb_();
	}
	}
	}

	// EOS is handled on this thread instead of in GetCurrentMediaTime(), because
	// GetCurrentMediaTime() is not guaranteed to be called.
	if (stop_called_ && !end_of_stream_played_.load()) {
	auto time_elapsed = SbTimeGetMonotonicNow() - stopped_at_;
	auto frames_played =
	time_elapsed * audio_sample_info_.samples_per_second / kSbTimeSecond;
	if (frames_played + playback_head_position_when_stopped_ >=
	total_frames_written_on_audio_track_thread_) {
	end_of_stream_played_.store(true);
	ended_cb_();
	SB_LOG(INFO) << "Audio playback ended, UpdateStatusAndWriteData stopped.";
	return;
	}
	}

	update_status_and_write_data_token_ = audio_track_thread_->Schedule(
	std::bind(&AudioRendererPassthrough::UpdateStatusAndWriteData, this,
	current_state),
	fully_written ? 0 : kAudioTrackUpdateInternal);
	}

	// This function can be called from any threads.
	void AudioRendererPassthrough::OnDecoderConsumed() {
	auto old_value = can_accept_more_data_.exchange(true);
	SB_DCHECK(!old_value);
	}

	// This function can be called from any threads.
	void AudioRendererPassthrough::OnDecoderOutput() {
	int decoded_audio_sample_rate;
	auto decoded_audio = decoder_->Read(&decoded_audio_sample_rate);
	SB_DCHECK(decoded_audio);

	ScopedLock scoped_lock(mutex_);
	decoded_audios_.push(decoded_audio);
	}

	} // namespace shared
	} // namespace android
	} // namespace starboard