[chromecast] Slew stream volume changes in StreamMixerAlsa.

chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc

 // Copyright 2015 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 "chromecast/media/cma/backend/alsa/stream_mixer_alsa.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <utility>
 
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "chromecast/base/chromecast_switches.h"
 #include "chromecast/media/cma/backend/alsa/alsa_wrapper.h"
 #include "chromecast/media/cma/backend/alsa/audio_filter_factory.h"
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h"
 #include "media/base/audio_bus.h"
 #include "media/base/media_switches.h"
-#include "media/base/vector_math.h"
 
 #define RETURN_REPORT_ERROR(snd_func, ...)                        \
   do {                                                            \
     int err = alsa_->snd_func(__VA_ARGS__);                       \
     if (err < 0) {                                                \
       LOG(ERROR) << #snd_func " error: " << alsa_->StrError(err); \
       SignalError();                                              \
       return;                                                     \
     }                                                             \
   } while (0)
@@ skipping 786 matching lines @@
   if (!temp_ || temp_->frames() < chunk_size) {
     temp_ = ::media::AudioBus::Create(kNumOutputChannels, chunk_size);
   }
 
   mixed_->ZeroFramesPartial(0, chunk_size);
 
   // Loop through active inputs, polling them for data, and mixing them.
   for (InputQueue* input : active_inputs) {
     input->GetResampledData(temp_.get(), chunk_size);
     for (int c = 0; c < kNumOutputChannels; ++c) {
-      float volume_scalar = input->volume_multiplier();
-      DCHECK(volume_scalar >= 0.0 && volume_scalar <= 1.0) << volume_scalar;
-      ::media::vector_math::FMAC(temp_->channel(c), volume_scalar, chunk_size,
-                                 mixed_->channel(c));
+      input->VolumeScaleAccumulate(temp_->channel(c), chunk_size,

[kmackay, 2016/09/15 01:51:36]

does this work properly? seems like it will slew one channel, and then continue
slewing the next channel, and so on (so channel 0 will slew from eg. 0.0 ->
0.05, and channel 1 will slew from 0.05 -> 0.1).

[jyw, 2016/09/15 22:16:23]

Done.

+                                   mixed_->channel(c));
     }
   }
 
   WriteMixedPcm(*mixed_, chunk_size, false /* is_silence */);
   return true;
 }
 
 ssize_t StreamMixerAlsa::BytesPerOutputFormatSample() {
   return alsa_->PcmFormatSize(pcm_format_, 1);
 }
@@ skipping 96 matching lines @@
   DCHECK(std::find(loopback_observers_.begin(), loopback_observers_.end(),
                    observer) != loopback_observers_.end());
   loopback_observers_.erase(std::remove(loopback_observers_.begin(),
                                         loopback_observers_.end(), observer),
                             loopback_observers_.end());
   observer->OnRemoved();
 }
 
 }  // namespace media
 }  // namespace chromecast