[PPAPI] Pepper MediaStream API audio track implementation and example.

content/renderer/pepper/pepper_media_stream_audio_track_host.cc

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/renderer/pepper/pepper_media_stream_audio_track_host.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/c/ppb_audio_frame.h"
+#include "ppapi/shared_impl/media_stream_frame.h"
+
+using media::AudioParameters;
+
+namespace {
+
+// Max audio buffer duration in milliseconds.
+const uint32_t kMaxDuration = 10;
+
+// TODO(penghuang): make this configurable.
+const int32_t kNumberOfFrames = 4;
+
+}  // namespace
+
+namespace content {
+
+PepperMediaStreamAudioTrackHost::AudioSink::AudioSink(
+    PepperMediaStreamAudioTrackHost* host)
+    : host_(host),
+      frame_data_size_(0),
+      main_message_loop_proxy_(base::MessageLoopProxy::current()),
+      weak_factory_(this) {
+}
+
+PepperMediaStreamAudioTrackHost::AudioSink::~AudioSink() {
+  DCHECK_EQ(main_message_loop_proxy_, base::MessageLoopProxy::current());
+}
+
+void PepperMediaStreamAudioTrackHost::AudioSink::EnqueueFrame(int32_t index) {
+  DCHECK_EQ(main_message_loop_proxy_, base::MessageLoopProxy::current());
+  DCHECK_GE(index, 0);
+  DCHECK_LT(index, host_->frame_buffer()->number_of_frames());
+  base::AutoLock lock(lock_);
+  frames_.push_back(index);
+}
+
+void PepperMediaStreamAudioTrackHost::AudioSink::InitFramesOnMainThread(
+    int32_t number_of_frames, int32_t frame_size) {
+  DCHECK_EQ(main_message_loop_proxy_, base::MessageLoopProxy::current());
+  bool result = host_->InitFrames(number_of_frames, frame_size);
+  DCHECK(result);
+  DCHECK_GE(host_->frame_buffer()->frame_size(), frame_size);

[yzshen1, 2014/02/04 18:26:13]

DCHECK is probably not sufficient: if somehow InitFrames() fails in release
builds, the code may continue running while frame_buffer()->frame_size() <
frame_size, and then we have buffer overflow on line 100.

As I said, we should either fail gracefully or die directly.

[Peng, 2014/02/04 19:57:31]

Sorry. I misunderstood your comment. I changed DCHECK to CHECK and added a TODO.

+  base::AutoLock lock(lock_);
+  for (int32_t i = 0; i < number_of_frames; ++i) {
+    int32_t index = host_->frame_buffer()->DequeueFrame();
+    DCHECK_GE(index, 0);
+    frames_.push_back(index);
+  }
+}
+
+void
+PepperMediaStreamAudioTrackHost::AudioSink::SendEnqueueFrameMessageOnMainThread(
+    int32_t index) {
+  DCHECK_EQ(main_message_loop_proxy_, base::MessageLoopProxy::current());
+  host_->SendEnqueueFrameMessageToPlugin(index);
+}
+
+void PepperMediaStreamAudioTrackHost::AudioSink::OnData(const int16* audio_data,
+                                                        int sample_rate,
+                                                        int number_of_channels,
+                                                        int number_of_frames) {
+  DCHECK(audio_thread_checker_.CalledOnValidThread());
+  DCHECK(audio_data);
+  DCHECK_EQ(sample_rate, audio_params_.sample_rate());
+  DCHECK_EQ(number_of_channels, audio_params_.channels());
+  DCHECK_EQ(number_of_frames, audio_params_.frames_per_buffer());
+  int32_t index = -1;
+  {
+    base::AutoLock lock(lock_);
+    if (!frames_.empty()) {
+      index = frames_.front();
+      frames_.pop_front();
+    }
+  }
+
+  if (index != -1) {
+    // TODO(penghuang): support re-sampling, etc.
+    ppapi::MediaStreamFrame::Audio* frame =
+        &(host_->frame_buffer()->GetFramePointer(index)->audio);
+    frame->header.size = host_->frame_buffer()->frame_size();
+    frame->header.type = ppapi::MediaStreamFrame::TYPE_AUDIO;
+    frame->timestamp = timestamp_.InMillisecondsF();
+    frame->sample_rate = static_cast<PP_AudioFrame_SampleRate>(sample_rate);
+    frame->number_of_channels = number_of_channels;
+    frame->number_of_samples = number_of_channels * number_of_frames;
+    frame->data_size = frame_data_size_;
+    memcpy(frame->data, audio_data, frame_data_size_);
+
+    main_message_loop_proxy_->PostTask(
+        FROM_HERE,
+        base::Bind(&AudioSink::SendEnqueueFrameMessageOnMainThread,
+                   weak_factory_.GetWeakPtr(), index));
+  }
+  timestamp_ += frame_duration_;
+}
+
+void PepperMediaStreamAudioTrackHost::AudioSink::OnSetFormat(
+    const AudioParameters& params) {
+  DCHECK(params.IsValid());
+  DCHECK_LE(params.GetBufferDuration().InMilliseconds(), kMaxDuration);
+  DCHECK_EQ(params.bits_per_sample(), 16);
+  DCHECK((params.sample_rate() == AudioParameters::kTelephoneSampleRate) ||
+         (params.sample_rate() == AudioParameters::kAudioCDSampleRate));
+
+  COMPILE_ASSERT(AudioParameters::kTelephoneSampleRate ==
+                 static_cast<int32_t>(PP_AUDIOFRAME_SAMPLERATE_8000),
+                 audio_sample_rate_does_not_match);
+  COMPILE_ASSERT(AudioParameters::kAudioCDSampleRate ==
+                 static_cast<int32_t>(PP_AUDIOFRAME_SAMPLERATE_44100),
+                 audio_sample_rate_does_not_match);
+  audio_params_ = params;
+
+  // TODO(penghuang): support setting format more than once.
+  frame_duration_ = params.GetBufferDuration();
+  frame_data_size_ = params.GetBytesPerBuffer();
+
+  if (original_audio_params_.IsValid()) {
+    DCHECK_EQ(params.sample_rate(), original_audio_params_.sample_rate());
+    DCHECK_EQ(params.bits_per_sample(),
+              original_audio_params_.bits_per_sample());
+    DCHECK_EQ(params.channels(), original_audio_params_.channels());
+  } else {
+    audio_thread_checker_.DetachFromThread();
+    original_audio_params_ = params;
+    // The size is slightly bigger than necessary, because 8 extra bytes are
+    // added into the struct. Also see |MediaStreamFrame|.
+    size_t max_frame_size =
+        params.sample_rate() * params.bits_per_sample() / 8 *
+        params.channels() * kMaxDuration / 1000;
+    size_t size = sizeof(ppapi::MediaStreamFrame::Audio) + max_frame_size;
+
+    main_message_loop_proxy_->PostTask(
+        FROM_HERE,
+        base::Bind(&AudioSink::InitFramesOnMainThread,
+                   weak_factory_.GetWeakPtr(),
+                   kNumberOfFrames,
+                   static_cast<int32_t>(size)));
+  }
+}
+
+PepperMediaStreamAudioTrackHost::PepperMediaStreamAudioTrackHost(
+    RendererPpapiHost* host,
+    PP_Instance instance,
+    PP_Resource resource,
+    const blink::WebMediaStreamTrack& track)
+    : PepperMediaStreamTrackHostBase(host, instance, resource),
+      track_(track),
+      connected_(false),
+      audio_sink_(this) {
+  DCHECK(!track_.isNull());
+}
+
+PepperMediaStreamAudioTrackHost::~PepperMediaStreamAudioTrackHost() {
+  OnClose();
+}
+
+void PepperMediaStreamAudioTrackHost::OnClose() {
+  if (connected_) {
+    MediaStreamAudioSink::RemoveFromAudioTrack(&audio_sink_, track_);
+    connected_ = false;
+  }
+}
+
+void PepperMediaStreamAudioTrackHost::OnNewFrameEnqueued() {
+  int32_t index = frame_buffer()->DequeueFrame();
+  DCHECK_GE(index, 0);
+  audio_sink_.EnqueueFrame(index);
+}
+
+void PepperMediaStreamAudioTrackHost::DidConnectPendingHostToResource() {
+  if (!connected_) {
+    MediaStreamAudioSink::AddToAudioTrack(&audio_sink_, track_);
+    connected_ = true;
+  }
+}
+
+}  // namespace content