Caching AudioOutputDevice instances in mixer manager

media/renderers/audio_renderer_impl.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/renderers/audio_renderer_impl.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <algorithm>
 #include <utility>
@@ skipping 18 matching lines @@
 #include "media/base/timestamp_constants.h"
 #include "media/filters/audio_clock.h"
 #include "media/filters/decrypting_demuxer_stream.h"
 
 namespace media {
 
 AudioRendererImpl::AudioRendererImpl(
     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
     media::AudioRendererSink* sink,
     ScopedVector<AudioDecoder> decoders,
-    const AudioHardwareConfig& hardware_config,
     const scoped_refptr<MediaLog>& media_log)
     : task_runner_(task_runner),
       expecting_config_changes_(false),
       sink_(sink),
       audio_buffer_stream_(
           new AudioBufferStream(task_runner, std::move(decoders), media_log)),
-      hardware_config_(hardware_config),
       media_log_(media_log),
       client_(nullptr),
       tick_clock_(new base::DefaultTickClock()),
       last_audio_memory_usage_(0),
       last_decoded_sample_rate_(0),
       playback_rate_(0.0),
       state_(kUninitialized),
       buffering_state_(BUFFERING_HAVE_NOTHING),
       rendering_(false),
       sink_playing_(false),
@@ skipping 269 matching lines @@
   DCHECK_EQ(kUninitialized, state_);
   DCHECK(sink_.get());
 
   state_ = kInitializing;
   client_ = client;
 
   // Always post |init_cb_| because |this| could be destroyed if initialization
   // failed.
   init_cb_ = BindToCurrentLoop(init_cb);
 
-  const AudioParameters& hw_params = hardware_config_.GetOutputConfig();
+  const AudioParameters& hw_params =

[DaleCurtis, 2016/05/26 19:18:09]

Do you know what this returns when the element is attached to WebAudio? If it
returns invalid parameters, that's actually good since we'll try to output at
input parameters which is best for WebAudio.

[o1ka, 2016/05/27 13:48:52]

This is a good question.

Here
https://code.google.com/p/chromium/codesearch#chromium/src/media/blink/webaud...

it returns device info with OUTPUT_DEVICE_STATUS_ERROR_INTERNAL and
UnavailableDeviceParams(defined here
https://code.google.com/p/chromium/codesearch#chromium/src/media/base/audio_p...)
which are valid, but AUDIO_FAKE, so we do fail back to input parameters here.

But in fact I'm not sure if it's correct. As far as I understand,
WebAudioSourceProviderImpl client can be reset by HTMLMediaElement to nullptr
later, which means rendering will switch to the real sink (ARMI). But pipeline
will continue to output at input parameters, which is a new behavior, and I'm
not sure that it's desired.
So, in order to keep the things as they are, I modified
WebAudioSourceProviderImpl to always return actual sink parameters no matter if
the client is set or not.

I can change that in a follow-up CL if you confirm that the new behavior is
valid.

(Note that if WebAudioSourceProvider is initialized with NullAudioSink  we do
output on input params here, because NullAudioSink params are AUDIO_FAKE)

+      sink_->GetOutputDeviceInfo().output_params();
   expecting_config_changes_ = stream->SupportsConfigChanges();
   if (!expecting_config_changes_ || !hw_params.IsValid() ||
       hw_params.format() == AudioParameters::AUDIO_FAKE) {
     // The actual buffer size is controlled via the size of the AudioBus
     // provided to Render(), so just choose something reasonable here for looks.
     int buffer_size = stream->audio_decoder_config().samples_per_second() / 100;
     audio_parameters_.Reset(
         AudioParameters::AUDIO_PCM_LOW_LATENCY,
         stream->audio_decoder_config().channel_layout(),
         stream->audio_decoder_config().samples_per_second(),
@@ skipping 579 matching lines @@
   DCHECK_NE(buffering_state_, buffering_state);
   lock_.AssertAcquired();
   buffering_state_ = buffering_state;
 
   task_runner_->PostTask(
       FROM_HERE, base::Bind(&AudioRendererImpl::OnBufferingStateChange,
                             weak_factory_.GetWeakPtr(), buffering_state_));
 }
 
 }  // namespace media