media/base/audio_pull_fifo.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/base/audio_pull_fifo.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "media/base/audio_bus.h"
  11
  12 namespace media {
  13
  14 AudioPullFifo::AudioPullFifo(int channels, int frames, const ReadCB& read_cb)
  15     : read_cb_(read_cb),
  16       fifo_(AudioBus::Create(channels, frames)),
  17       fifo_index_(frames) {}
  18
  19 AudioPullFifo::~AudioPullFifo() {}
  20
  21 void AudioPullFifo::Consume(AudioBus* destination, int frames_to_consume) {
  22   DCHECK_LE(frames_to_consume, destination->frames());
  23
  24   int remaining_frames_to_provide = frames_to_consume;
  25
  26   // Try to fulfill the request using what's available in the FIFO.
  27   int frames_read = ReadFromFifo(destination, remaining_frames_to_provide, 0);
  28   int write_pos = frames_read;
  29   remaining_frames_to_provide -= frames_read;
  30
  31   // Get the remaining audio frames from the producer using the callback.
  32   while (remaining_frames_to_provide > 0) {
  33     DCHECK_EQ(fifo_index_, fifo_->frames());
  34     fifo_index_ = 0;
  35
  36     // Fill up the FIFO by acquiring audio data from the producer.
  37     read_cb_.Run(write_pos, fifo_.get());
  38
  39     // Try to fulfill the request using what's available in the FIFO.
  40     frames_read =
  41         ReadFromFifo(destination, remaining_frames_to_provide, write_pos);
  42     write_pos += frames_read;
  43     remaining_frames_to_provide -= frames_read;
  44   }
  45 }
  46
  47 void AudioPullFifo::Clear() { fifo_index_ = fifo_->frames(); }
  48
  49 int AudioPullFifo::ReadFromFifo(AudioBus* destination,
  50                                 int frames_to_provide,
  51                                 int write_pos) {
  52   int frames = std::min(frames_to_provide, fifo_->frames() - fifo_index_);
  53   if (frames <= 0)
  54     return 0;
  55
  56   for (int ch = 0; ch < fifo_->channels(); ++ch) {
  57     const float* src = fifo_->channel(ch) + fifo_index_;
  58     float* dest = destination->channel(ch) + write_pos;
  59     memcpy(dest, src, frames * sizeof(*src));
  60   }
  61
  62   fifo_index_ += frames;
  63   return frames;
  64 }
  65
  66 }  // namespace media