Introduce AudioOutputResampler for browser side resampling.

media/audio/audio_output_resampler.cc

+// Copyright (c) 2012 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 "media/audio/audio_output_resampler.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/stringprintf.h"
+#include "base/compiler_specific.h"

[scherkus (not reviewing), 2012/09/07 13:30:16]

a->z ordering

[DaleCurtis, 2012/09/10 12:06:24]

Removed.

+#include "base/message_loop.h"
+#include "base/time.h"
+#include "media/audio/audio_io.h"
+#include "media/audio/audio_output_dispatcher_impl.h"
+#include "media/audio/audio_output_proxy.h"
+#include "media/audio/audio_util.h"
+#include "media/base/audio_fifo.h"
+#include "media/base/multi_channel_resampler.h"
+
+
+namespace media {
+
+AudioOutputResampler::AudioOutputResampler(AudioManager* audio_manager,
+                                           const AudioParameters& input_params,
+                                           const base::TimeDelta& close_delay)
+    : AudioOutputDispatcher(audio_manager, input_params),
+      source_callback_(NULL),
+      outstanding_audio_bytes_(0),
+      io_ratio_(0),
+      output_bytes_per_frame_(0),
+      input_bytes_per_frame_(0) {
+  AudioParameters output_params = input_params;
+  int hardware_sample_rate = GetAudioHardwareSampleRate();
+  int hardware_buffer_size = GetAudioHardwareBufferSize();
+
+  // Only resample if necessary since it's expensive.
+  // TODO(dalecurtis): Restrict to PCM low latency before landing.  Right now it
+  // converts all non-low latency calls as well for testing.
+  if (input_params.sample_rate() != hardware_sample_rate ||
+      input_params.frames_per_buffer() != hardware_buffer_size) {
+    // Create output parameters based on the audio hardware configuration.
+    // TODO(dalecurtis): This should include channel count and bit depth.
+    output_params = AudioParameters(
+        AudioParameters::AUDIO_PCM_LOW_LATENCY, input_params.channel_layout(),
+        hardware_sample_rate, 16, GetAudioHardwareBufferSize());
+    input_bytes_per_frame_ = input_params.GetBytesPerFrame();
+    output_bytes_per_frame_ = output_params.GetBytesPerFrame();
+
+    // Calculate the first part of the I/O ratio for the resampler.
+    io_ratio_ =
+        input_params.sample_rate() / static_cast<double>(hardware_sample_rate);
+    resampler_.reset(new MultiChannelResampler(
+        output_params.channels(),
+        io_ratio_,
+        base::Bind(
+            &AudioOutputResampler::ProvideInput, base::Unretained(this))));
+
+    // Include the difference in output bits per sample.
+    io_ratio_ *= static_cast<double>(input_params.bits_per_sample()) /
+        output_params.bits_per_sample();
+
+    // TODO(dalecurtis): Initialize AudioPullFIFO(input_params.buffer_frames()).
+    temp_bus_ = AudioBus::Create(input_params);
+    audio_fifo_.reset(new AudioFifo(

[Chris Rogers, 2012/09/06 19:18:25]

Even if we're not doing sample-rate conversion, we still might need the FIFO to
match the client buffer size vs. the hardware buffer size.

[DaleCurtis, 2012/09/07 14:17:35]

Good point, I'll rework it so buffer size differences bypass the resampler.

[DaleCurtis, 2012/09/10 12:06:24]

Done.

+        input_params.channels(), input_params.frames_per_buffer()));
+  }
+
+  // TODO(dalecurtis): All this code should be merged into AudioOutputMixer once
+  // we've stabilized the issues there.
+  dispatcher_ = new AudioOutputDispatcherImpl(
+      audio_manager, output_params, close_delay);
+}
+
+AudioOutputResampler::~AudioOutputResampler() {}
+
+bool AudioOutputResampler::OpenStream() {
+  return dispatcher_->OpenStream();
+}
+
+bool AudioOutputResampler::StartStream(
+    AudioOutputStream::AudioSourceCallback* callback,
+    AudioOutputProxy* stream_proxy) {
+  {
+    base::AutoLock auto_lock(source_lock_);
+    source_callback_ = callback;
+  }
+  return dispatcher_->StartStream(this, stream_proxy);

[scherkus (not reviewing), 2012/09/07 13:30:16]

which thread is calling these methods?

is dispatcher_ also thread safe?

[DaleCurtis, 2012/09/07 14:17:35]

Called by the audio thread, AudioOutputDispatcherImpl has,  
DCHECK_EQ(MessageLoop::current(), message_loop_); everywhere so it's fine. I can
duplicate those checks here if we want.

|dispatcher_| itself is initialized during the constructor, so it's fine.

+}
+
+void AudioOutputResampler::StopStream(AudioOutputProxy* stream_proxy) {
+  {
+    base::AutoLock auto_lock(source_lock_);
+    source_callback_ = NULL;
+    outstanding_audio_bytes_ = 0;
+    audio_fifo_->Clear();
+    resampler_->Flush();
+  }
+  dispatcher_->StopStream(stream_proxy);
+}
+
+void AudioOutputResampler::StreamVolumeSet(AudioOutputProxy* stream_proxy,
+                                           double volume) {
+  dispatcher_->StreamVolumeSet(stream_proxy, volume);
+}
+
+void AudioOutputResampler::CloseStream(AudioOutputProxy* stream_proxy) {
+  {
+    base::AutoLock auto_lock(source_lock_);
+    source_callback_ = NULL;
+    outstanding_audio_bytes_ = 0;
+    audio_fifo_->Clear();
+    resampler_->Flush();
+  }
+  dispatcher_->CloseStream(stream_proxy);
+}
+
+void AudioOutputResampler::Shutdown() {
+  {
+    base::AutoLock auto_lock(source_lock_);
+    source_callback_ = NULL;
+    outstanding_audio_bytes_ = 0;
+    audio_fifo_->Clear();
+    resampler_->Flush();
+  }
+  dispatcher_->Shutdown();
+}
+
+int AudioOutputResampler::OnMoreData(AudioBus* audio_bus,
+                                     AudioBuffersState buffers_state) {
+  if (!resampler_.get()) {
+    // TODO(dalecurtis): Copy ASB to local variable, release lock prior to call?

[scherkus (not reviewing), 2012/09/07 13:30:16]

what's ASB?

[DaleCurtis, 2012/09/07 14:17:35]

A typo :) Should be ASCB.. Essentially instead of holding the lock for
source_callback_, copy it to a local variable and then call it, so the
OnMoreData() call isn't blocked by any callers.

+    base::AutoLock auto_lock(source_lock_);
+    return source_callback_->OnMoreData(audio_bus, buffers_state);

[Chris Rogers, 2012/09/06 19:18:25]

We need to have a conditional here to check if we need to use the FIFO (when
client buffer size does not match hardware buffer size).

[DaleCurtis, 2012/09/07 14:17:35]

Will investigate, shouldn't be too hard.

[DaleCurtis, 2012/09/10 12:06:24]

Done.

+  }
+
+  current_buffers_state_ = buffers_state;
+  resampler_->Resample(audio_bus, audio_bus->frames());
+
+  // Calculate how much data is left in the internal FIFO and resampler buffers.
+  outstanding_audio_bytes_ -= audio_bus->frames() * output_bytes_per_frame_;
+  CHECK_GE(outstanding_audio_bytes_, 0);
+
+  // Always return the full number of frames requested, ProvideInput() will pad
+  // with silence if it wasn't able to acquire enough data.
+  // NOTE: This will not work with the current non-low latency <audio> pipeline.
+  return audio_bus->frames();
+}
+
+void AudioOutputResampler::ProvideInput(AudioBus* audio_bus) {
+  // TODO(dalecurtis): Copy ASB to local variable, release lock prior to call?
+  base::AutoLock auto_lock(source_lock_);
+  // We may have waited for |source_lock_| while a call cleared the callback.
+  if (!source_callback_)
+    return;
+
+  // Serve frames out of the FIFO if they're available.
+  int frames_to_write = audio_bus->frames();
+  if (audio_fifo_->frames_in_fifo() > 0) {
+    int frames = std::min(audio_bus->frames(), audio_fifo_->frames_in_fifo());
+    CHECK(audio_fifo_->Consume(audio_bus, 0, frames));

[scherkus (not reviewing), 2012/09/07 13:30:17]

:)

+    frames_to_write -= frames;
+  }
+
+  // If we were able to fulfill the request from the FIFO, we're done.
+  if (frames_to_write == 0)
+    return;
+
+  // Adjust playback delay to include the state of the internal buffers used by
+  // the resampler and the FIFO.  Since the sample rate and bits per channel
+  // may be different, we need to scale this value appropriately
+  // TODO(dalecurtis): Move to the FIFO side callback once the FIFO is added.
+  AudioBuffersState new_buffers_state;
+  new_buffers_state.pending_bytes = io_ratio_ *
+      (current_buffers_state_.total_bytes() + outstanding_audio_bytes_);
+
+  // Retrieve data from the original callback.
+  int frames = source_callback_->OnMoreData(temp_bus_.get(), new_buffers_state);
+
+  // TODO(dalecurtis): Technically only <audio> returns fewer frames than
+  // requested and it won't use this path... but since I tested with <audio> on
+  // the high latency path it was necessary.  Remove later.
+
+  // Scale the number of frames we got back in terms of input bytes to output
+  // bytes accordingly.
+  outstanding_audio_bytes_ += (frames * input_bytes_per_frame_) / io_ratio_;
+
+  // Put everything into the FIFO and fulfill the rest of the request.
+  CHECK(audio_fifo_->Push(temp_bus_.get(), frames));
+  CHECK(audio_fifo_->Consume(
+      audio_bus, audio_bus->frames() - frames_to_write, frames_to_write));
+}
+
+void AudioOutputResampler::OnError(AudioOutputStream* stream, int code) {
+  // TODO(dalecurtis): Copy ASB to local variable, release lock prior to call?
+  base::AutoLock auto_lock(source_lock_);
+  if (source_callback_)
+    source_callback_->OnError(stream, code);
+}
+
+void AudioOutputResampler::WaitTillDataReady() {
+  // TODO(dalecurtis): Copy ASB to local variable, release lock prior to call?
+  base::AutoLock auto_lock(source_lock_);
+  if (source_callback_ && !outstanding_audio_bytes_)
+    source_callback_->WaitTillDataReady();
+}
+
+}  // namespace media