media/cast/receiver/audio_decoder.cc

   1 // Copyright 2014 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/cast/receiver/audio_decoder.h"
   6
   7 #include "base/bind.h"
   8 #include "base/bind_helpers.h"
   9 #include "base/location.h"
  10 #include "base/logging.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "base/sys_byteorder.h"
  13 #include "media/cast/cast_defines.h"
  14 #include "third_party/opus/src/include/opus.h"
  15
  16 namespace media {
  17 namespace cast {
  18
  19 // Base class that handles the common problem of detecting dropped frames, and
  20 // then invoking the Decode() method implemented by the subclasses to convert
  21 // the encoded payload data into usable audio data.
  22 class AudioDecoder::ImplBase
  23     : public base::RefCountedThreadSafe<AudioDecoder::ImplBase> {
  24  public:
  25   ImplBase(const scoped_refptr<CastEnvironment>& cast_environment,
  26            Codec codec,
  27            int num_channels,
  28            int sampling_rate)
  29       : cast_environment_(cast_environment),
  30         codec_(codec),
  31         num_channels_(num_channels),
  32         cast_initialization_status_(STATUS_AUDIO_UNINITIALIZED),
  33         seen_first_frame_(false) {
  34     if (num_channels_ <= 0 || sampling_rate <= 0 || sampling_rate % 100 != 0)
  35       cast_initialization_status_ = STATUS_INVALID_AUDIO_CONFIGURATION;
  36   }
  37
  38   CastInitializationStatus InitializationResult() const {
  39     return cast_initialization_status_;
  40   }
  41
  42   void DecodeFrame(scoped_ptr<EncodedFrame> encoded_frame,
  43                    const DecodeFrameCallback& callback) {
  44     DCHECK_EQ(cast_initialization_status_, STATUS_AUDIO_INITIALIZED);
  45
  46     static_assert(sizeof(encoded_frame->frame_id) == sizeof(last_frame_id_),
  47                   "size of frame_id types do not match");
  48     bool is_continuous = true;
  49     if (seen_first_frame_) {
  50       const uint32 frames_ahead = encoded_frame->frame_id - last_frame_id_;
  51       if (frames_ahead > 1) {
  52         RecoverBecauseFramesWereDropped();
  53         is_continuous = false;
  54       }
  55     } else {
  56       seen_first_frame_ = true;
  57     }
  58     last_frame_id_ = encoded_frame->frame_id;
  59
  60     scoped_ptr<AudioBus> decoded_audio = Decode(
  61         encoded_frame->mutable_bytes(),
  62         static_cast<int>(encoded_frame->data.size()));
  63     cast_environment_->PostTask(CastEnvironment::MAIN,
  64                                 FROM_HERE,
  65                                 base::Bind(callback,
  66                                            base::Passed(&decoded_audio),
  67                                            is_continuous));
  68   }
  69
  70  protected:
  71   friend class base::RefCountedThreadSafe<ImplBase>;
  72   virtual ~ImplBase() {}
  73
  74   virtual void RecoverBecauseFramesWereDropped() {}
  75
  76   // Note: Implementation of Decode() is allowed to mutate |data|.
  77   virtual scoped_ptr<AudioBus> Decode(uint8* data, int len) = 0;
  78
  79   const scoped_refptr<CastEnvironment> cast_environment_;
  80   const Codec codec_;
  81   const int num_channels_;
  82
  83   // Subclass' ctor is expected to set this to STATUS_AUDIO_INITIALIZED.
  84   CastInitializationStatus cast_initialization_status_;
  85
  86  private:
  87   bool seen_first_frame_;
  88   uint32 last_frame_id_;
  89
  90   DISALLOW_COPY_AND_ASSIGN(ImplBase);
  91 };
  92
  93 class AudioDecoder::OpusImpl : public AudioDecoder::ImplBase {
  94  public:
  95   OpusImpl(const scoped_refptr<CastEnvironment>& cast_environment,
  96            int num_channels,
  97            int sampling_rate)
  98       : ImplBase(cast_environment,
  99                  CODEC_AUDIO_OPUS,
 100                  num_channels,
 101                  sampling_rate),
 102         decoder_memory_(new uint8[opus_decoder_get_size(num_channels)]),
 103         opus_decoder_(reinterpret_cast<OpusDecoder*>(decoder_memory_.get())),
 104         max_samples_per_frame_(
 105             kOpusMaxFrameDurationMillis * sampling_rate / 1000),
 106         buffer_(new float[max_samples_per_frame_ * num_channels]) {
 107     if (ImplBase::cast_initialization_status_ != STATUS_AUDIO_UNINITIALIZED)
 108       return;
 109     if (opus_decoder_init(opus_decoder_, sampling_rate, num_channels) !=
 110             OPUS_OK) {
 111       ImplBase::cast_initialization_status_ =
 112           STATUS_INVALID_AUDIO_CONFIGURATION;
 113       return;
 114     }
 115     ImplBase::cast_initialization_status_ = STATUS_AUDIO_INITIALIZED;
 116   }
 117
 118  private:
 119   ~OpusImpl() override {}
 120
 121   void RecoverBecauseFramesWereDropped() override {
 122     // Passing NULL for the input data notifies the decoder of frame loss.
 123     const opus_int32 result =
 124         opus_decode_float(
 125             opus_decoder_, NULL, 0, buffer_.get(), max_samples_per_frame_, 0);
 126     DCHECK_GE(result, 0);
 127   }
 128
 129   scoped_ptr<AudioBus> Decode(uint8* data, int len) override {
 130     scoped_ptr<AudioBus> audio_bus;
 131     const opus_int32 num_samples_decoded = opus_decode_float(
 132         opus_decoder_, data, len, buffer_.get(), max_samples_per_frame_, 0);
 133     if (num_samples_decoded <= 0)
 134       return audio_bus.Pass();  // Decode error.
 135
 136     // Copy interleaved samples from |buffer_| into a new AudioBus (where
 137     // samples are stored in planar format, for each channel).
 138     audio_bus = AudioBus::Create(num_channels_, num_samples_decoded).Pass();
 139     // TODO(miu): This should be moved into AudioBus::FromInterleaved().
 140     for (int ch = 0; ch < num_channels_; ++ch) {
 141       const float* src = buffer_.get() + ch;
 142       const float* const src_end = src + num_samples_decoded * num_channels_;
 143       float* dest = audio_bus->channel(ch);
 144       for (; src < src_end; src += num_channels_, ++dest)
 145         *dest = *src;
 146     }
 147     return audio_bus.Pass();
 148   }
 149
 150   const scoped_ptr<uint8[]> decoder_memory_;
 151   OpusDecoder* const opus_decoder_;
 152   const int max_samples_per_frame_;
 153   const scoped_ptr<float[]> buffer_;
 154
 155   // According to documentation in third_party/opus/src/include/opus.h, we must
 156   // provide enough space in |buffer_| to contain 120ms of samples.  At 48 kHz,
 157   // then, that means 5760 samples times the number of channels.
 158   static const int kOpusMaxFrameDurationMillis = 120;
 159
 160   DISALLOW_COPY_AND_ASSIGN(OpusImpl);
 161 };
 162
 163 class AudioDecoder::Pcm16Impl : public AudioDecoder::ImplBase {
 164  public:
 165   Pcm16Impl(const scoped_refptr<CastEnvironment>& cast_environment,
 166             int num_channels,
 167             int sampling_rate)
 168       : ImplBase(cast_environment,
 169                  CODEC_AUDIO_PCM16,
 170                  num_channels,
 171                  sampling_rate) {
 172     if (ImplBase::cast_initialization_status_ != STATUS_AUDIO_UNINITIALIZED)
 173       return;
 174     ImplBase::cast_initialization_status_ = STATUS_AUDIO_INITIALIZED;
 175   }
 176
 177  private:
 178   ~Pcm16Impl() override {}
 179
 180   scoped_ptr<AudioBus> Decode(uint8* data, int len) override {
 181     scoped_ptr<AudioBus> audio_bus;
 182     const int num_samples = len / sizeof(int16) / num_channels_;
 183     if (num_samples <= 0)
 184       return audio_bus.Pass();
 185
 186     int16* const pcm_data = reinterpret_cast<int16*>(data);
 187 #if defined(ARCH_CPU_LITTLE_ENDIAN)
 188     // Convert endianness.
 189     const int num_elements = num_samples * num_channels_;
 190     for (int i = 0; i < num_elements; ++i)
 191       pcm_data[i] = static_cast<int16>(base::NetToHost16(pcm_data[i]));
 192 #endif
 193     audio_bus = AudioBus::Create(num_channels_, num_samples).Pass();
 194     audio_bus->FromInterleaved(pcm_data, num_samples, sizeof(int16));
 195     return audio_bus.Pass();
 196   }
 197
 198   DISALLOW_COPY_AND_ASSIGN(Pcm16Impl);
 199 };
 200
 201 AudioDecoder::AudioDecoder(
 202     const scoped_refptr<CastEnvironment>& cast_environment,
 203     int channels,
 204     int sampling_rate,
 205     Codec codec)
 206     : cast_environment_(cast_environment) {
 207   switch (codec) {
 208     case CODEC_AUDIO_OPUS:
 209       impl_ = new OpusImpl(cast_environment, channels, sampling_rate);
 210       break;
 211     case CODEC_AUDIO_PCM16:
 212       impl_ = new Pcm16Impl(cast_environment, channels, sampling_rate);
 213       break;
 214     default:
 215       NOTREACHED() << "Unknown or unspecified codec.";
 216       break;
 217   }
 218 }
 219
 220 AudioDecoder::~AudioDecoder() {}
 221
 222 CastInitializationStatus AudioDecoder::InitializationResult() const {
 223   if (impl_.get())
 224     return impl_->InitializationResult();
 225   return STATUS_UNSUPPORTED_AUDIO_CODEC;
 226 }
 227
 228 void AudioDecoder::DecodeFrame(
 229     scoped_ptr<EncodedFrame> encoded_frame,
 230     const DecodeFrameCallback& callback) {
 231   DCHECK(encoded_frame.get());
 232   DCHECK(!callback.is_null());
 233   if (!impl_.get() ||
 234       impl_->InitializationResult() != STATUS_AUDIO_INITIALIZED) {
 235     callback.Run(make_scoped_ptr<AudioBus>(NULL), false);
 236     return;
 237   }
 238   cast_environment_->PostTask(CastEnvironment::AUDIO,
 239                               FROM_HERE,
 240                               base::Bind(&AudioDecoder::ImplBase::DecodeFrame,
 241                                          impl_,
 242                                          base::Passed(&encoded_frame),
 243                                          callback));
 244 }
 245
 246 }  // namespace cast
 247 }  // namespace media