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// Copyright 2016 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/base/silent_sink_suspender.h"
#include "base/single_thread_task_runner.h"
#include "base/threading/thread_task_runner_handle.h"
namespace media {
SilentSinkSuspender::SilentSinkSuspender(
AudioRendererSink::RenderCallback* callback,
base::TimeDelta silence_timeout,
const AudioParameters& params,
const scoped_refptr<AudioRendererSink>& sink,
const scoped_refptr<base::SingleThreadTaskRunner>& worker)
: callback_(callback),
params_(params),
sink_(sink),
task_runner_(base::ThreadTaskRunnerHandle::Get()),
silence_timeout_(silence_timeout),
fake_sink_(worker, params_),
sink_transition_callback_(
base::Bind(&SilentSinkSuspender::TransitionSinks,
base::Unretained(this))) {
DCHECK(params_.IsValid());
DCHECK(sink_);
DCHECK(callback_);
DCHECK(task_runner_->BelongsToCurrentThread());
}
SilentSinkSuspender::~SilentSinkSuspender() {
DCHECK(task_runner_->BelongsToCurrentThread());
fake_sink_.Stop();
}
int SilentSinkSuspender::Render(base::TimeDelta delay,
base::TimeTicks delay_timestamp,
int prior_frames_skipped,
AudioBus* dest) {
// Lock required since AudioRendererSink::Pause() is not synchronous, we need
// to discard these calls during the transition to the fake sink.
base::AutoLock al(transition_lock_);
if (is_using_fake_sink_ && dest) {
// Audio should be silent at this point, if not, it will be handled once the
// transition to the fake sink is complete.
dest->Zero();
return dest->frames();
}
// When we're using the |fake_sink_| a null destination will be sent; we store
// the audio data for a future transition out of silence.
if (!dest) {
DCHECK(is_using_fake_sink_);
DCHECK_EQ(prior_frames_skipped, 0);
// |delay_timestamp| contains the value cached at
// |latest_output_delay_timestamp_|
// so we simulate the real sink output, promoting |delay_timestamp| with
// |elapsedTime|.
DCHECK_EQ(delay_timestamp, latest_output_delay_timestamp_);
base::TimeDelta elapsedTime =
base::TimeTicks::Now() - fake_sink_transition_time_;
delay_timestamp += elapsedTime;
// If we have no buffers or a transition is pending, one or more extra
// Render() calls have occurred in before TransitionSinks() can run, so we
// store this data for the eventual transition.
if (buffers_after_silence_.empty() || is_transition_pending_)
buffers_after_silence_.push_back(AudioBus::Create(params_));
dest = buffers_after_silence_.back().get();
} else if (!buffers_after_silence_.empty()) {
// Drain any non-silent transitional buffers before queuing more audio data.
// Note: These do not skew clocks derived from frame count since we don't
// issue Render() to the client when returning these buffers.
DCHECK(!is_using_fake_sink_);
buffers_after_silence_.front()->CopyTo(dest);
buffers_after_silence_.pop_front();
return dest->frames();
}
// Pass-through to client and request rendering.
callback_->Render(delay, delay_timestamp, prior_frames_skipped, dest);
// Check for silence or real audio data and transition if necessary.
if (!dest->AreFramesZero()) {
first_silence_time_ = base::TimeTicks();
if (is_using_fake_sink_) {
is_transition_pending_ = true;
task_runner_->PostTask(
FROM_HERE,
base::BindOnce(sink_transition_callback_.callback(), false));
return dest->frames();
}
} else if (!is_using_fake_sink_) {
const base::TimeTicks now = base::TimeTicks::Now();
if (first_silence_time_.is_null())
first_silence_time_ = now;
if (now - first_silence_time_ > silence_timeout_) {
is_transition_pending_ = true;
latest_output_delay_ = delay;
latest_output_delay_timestamp_ = delay_timestamp;
fake_sink_transition_time_ = now;
task_runner_->PostTask(
FROM_HERE,
base::BindOnce(sink_transition_callback_.callback(), true));
}
}
return dest->frames();
}
void SilentSinkSuspender::OnRenderError() {
callback_->OnRenderError();
}
bool SilentSinkSuspender::IsUsingFakeSinkForTesting() {
base::AutoLock al(transition_lock_);
return is_using_fake_sink_;
}
void SilentSinkSuspender::TransitionSinks(bool use_fake_sink) {
DCHECK(task_runner_->BelongsToCurrentThread());
// Ignore duplicate requests which can occur if the transition takes too long
// and multiple Render() events occur.
{
base::AutoLock al(transition_lock_);
if (use_fake_sink == is_using_fake_sink_)
return;
}
if (use_fake_sink) {
sink_->Pause();
// |sink_| may still be executing Render() at this point or even sometime
// after this point, so we must acquire the lock to make sure we don't have
// concurrent Render() execution. Once |is_using_fake_sink_| is set to true,
// calls from |sink_| will be dropped.
{
base::AutoLock al(transition_lock_);
is_transition_pending_ = false;
is_using_fake_sink_ = true;
}
fake_sink_.Start(
base::Bind(base::IgnoreResult(&SilentSinkSuspender::Render),
base::Unretained(this), latest_output_delay_,
latest_output_delay_timestamp_, 0, nullptr));
} else {
fake_sink_.Stop();
// Despite the fake sink having a synchronous Stop(), if this transition
// occurs too soon after pausing the real sink, we may have pending Render()
// calls from before the transition to the fake sink. As such, we need to
// hold the lock here to avoid any races.
{
base::AutoLock al(transition_lock_);
is_transition_pending_ = false;
is_using_fake_sink_ = false;
}
sink_->Play();
}
}
} // namespace content
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