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      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
     95