content/renderer/media/audio_decoder.cc

   1 // Copyright 2013 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 "content/renderer/media/audio_decoder.h"
   6
   7 #include <vector>
   8
   9 #include "base/basictypes.h"
  10 #include "base/strings/string_util.h"
  11 #include "base/time/time.h"
  12 #include "media/base/audio_bus.h"
  13 #include "media/base/limits.h"
  14 #include "media/filters/audio_file_reader.h"
  15 #include "media/filters/in_memory_url_protocol.h"
  16 #include "third_party/WebKit/public/platform/WebAudioBus.h"
  17
  18 using media::AudioBus;
  19 using media::AudioFileReader;
  20 using media::InMemoryUrlProtocol;
  21 using std::vector;
  22 using blink::WebAudioBus;
  23
  24 namespace content {
  25
  26 // Decode in-memory audio file data.
  27 bool DecodeAudioFileData(
  28     blink::WebAudioBus* destination_bus,
  29     const char* data, size_t data_size) {
  30   DCHECK(destination_bus);
  31   if (!destination_bus)
  32     return false;
  33
  34   // Uses the FFmpeg library for audio file reading.
  35   InMemoryUrlProtocol url_protocol(reinterpret_cast<const uint8*>(data),
  36                                    data_size, false);
  37   AudioFileReader reader(&url_protocol);
  38
  39   if (!reader.Open())
  40     return false;
  41
  42   size_t number_of_channels = reader.channels();
  43   double file_sample_rate = reader.sample_rate();
  44   size_t number_of_frames = static_cast<size_t>(reader.GetNumberOfFrames());
  45
  46   // Apply sanity checks to make sure crazy values aren't coming out of
  47   // FFmpeg.
  48   if (!number_of_channels ||
  49       number_of_channels > static_cast<size_t>(media::limits::kMaxChannels) ||
  50       file_sample_rate < media::limits::kMinSampleRate ||
  51       file_sample_rate > media::limits::kMaxSampleRate)
  52     return false;
  53
  54   // Allocate and configure the output audio channel data.
  55   destination_bus->initialize(number_of_channels,
  56                               number_of_frames,
  57                               file_sample_rate);
  58
  59   // Wrap the channel pointers which will receive the decoded PCM audio.
  60   vector<float*> audio_data;
  61   audio_data.reserve(number_of_channels);
  62   for (size_t i = 0; i < number_of_channels; ++i) {
  63     audio_data.push_back(destination_bus->channelData(i));
  64   }
  65
  66   scoped_ptr<AudioBus> audio_bus = AudioBus::WrapVector(
  67       number_of_frames, audio_data);
  68
  69   // Decode the audio file data.
  70   // TODO(crogers): If our estimate was low, then we still may fail to read
  71   // all of the data from the file.
  72   size_t actual_frames = reader.Read(audio_bus.get());
  73
  74   // Adjust WebKit's bus to account for the actual file length
  75   // and valid data read.
  76   if (actual_frames != number_of_frames) {
  77     DCHECK_LE(actual_frames, number_of_frames);
  78     destination_bus->resizeSmaller(actual_frames);
  79   }
  80
  81   double duration = actual_frames / file_sample_rate;
  82
  83   DVLOG(1) << "Decoded file data -"
  84            << " data: " << data
  85            << " data size: " << data_size
  86            << " duration: " << duration
  87            << " number of frames: " << actual_frames
  88            << " sample rate: " << file_sample_rate
  89            << " number of channels: " << number_of_channels;
  90
  91   return actual_frames > 0;
  92 }
  93
  94 }  // namespace content