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