modules/audio_coding/codecs/g722/audio_encoder_g722.cc

/*
 *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "webrtc/modules/audio_coding/codecs/g722/include/audio_encoder_g722.h"

#include <limits>
#include "webrtc/base/checks.h"
#include "webrtc/common_types.h"
#include "webrtc/modules/audio_coding/codecs/g722/include/g722_interface.h"

namespace webrtc {

namespace {

const size_t kSampleRateHz = 16000;

AudioEncoderG722::Config CreateConfig(const CodecInst& codec_inst) {
  AudioEncoderG722::Config config;
  config.num_channels = codec_inst.channels;
  config.frame_size_ms = codec_inst.pacsize / 16;
  config.payload_type = codec_inst.pltype;
  return config;
}

}  // namespace

bool AudioEncoderG722::Config::IsOk() const {
  return (frame_size_ms > 0) && (frame_size_ms % 10 == 0) &&
      (num_channels >= 1);
}

AudioEncoderG722::AudioEncoderG722(const Config& config)
    : num_channels_(config.num_channels),
      payload_type_(config.payload_type),
      num_10ms_frames_per_packet_(
          static_cast<size_t>(config.frame_size_ms / 10)),
      num_10ms_frames_buffered_(0),
      first_timestamp_in_buffer_(0),
      encoders_(new EncoderState[num_channels_]),
      interleave_buffer_(2 * num_channels_) {
  RTC_CHECK(config.IsOk());
  const size_t samples_per_channel =
      kSampleRateHz / 100 * num_10ms_frames_per_packet_;
  for (int i = 0; i < num_channels_; ++i) {
    encoders_[i].speech_buffer.reset(new int16_t[samples_per_channel]);
    encoders_[i].encoded_buffer.SetSize(samples_per_channel / 2);
  }
  Reset();
}

AudioEncoderG722::AudioEncoderG722(const CodecInst& codec_inst)
    : AudioEncoderG722(CreateConfig(codec_inst)) {}

AudioEncoderG722::~AudioEncoderG722() = default;

size_t AudioEncoderG722::MaxEncodedBytes() const {
  return SamplesPerChannel() / 2 * num_channels_;
}

int AudioEncoderG722::SampleRateHz() const {
  return kSampleRateHz;
}

int AudioEncoderG722::NumChannels() const {
  return num_channels_;
}

int AudioEncoderG722::RtpTimestampRateHz() const {
  // The RTP timestamp rate for G.722 is 8000 Hz, even though it is a 16 kHz
  // codec.
  return kSampleRateHz / 2;
}

size_t AudioEncoderG722::Num10MsFramesInNextPacket() const {
  return num_10ms_frames_per_packet_;
}

size_t AudioEncoderG722::Max10MsFramesInAPacket() const {
  return num_10ms_frames_per_packet_;
}

int AudioEncoderG722::GetTargetBitrate() const {
  // 4 bits/sample, 16000 samples/s/channel.
  return 64000 * NumChannels();
}

AudioEncoder::EncodedInfo AudioEncoderG722::EncodeInternal(
    uint32_t rtp_timestamp,
    const int16_t* audio,
    size_t max_encoded_bytes,
    uint8_t* encoded) {
  RTC_CHECK_GE(max_encoded_bytes, MaxEncodedBytes());

  if (num_10ms_frames_buffered_ == 0)
    first_timestamp_in_buffer_ = rtp_timestamp;

  // Deinterleave samples and save them in each channel's buffer.
  const size_t start = kSampleRateHz / 100 * num_10ms_frames_buffered_;
  for (size_t i = 0; i < kSampleRateHz / 100; ++i)
    for (int j = 0; j < num_channels_; ++j)
      encoders_[j].speech_buffer[start + i] = audio[i * num_channels_ + j];

  // If we don't yet have enough samples for a packet, we're done for now.
  if (++num_10ms_frames_buffered_ < num_10ms_frames_per_packet_) {
    return EncodedInfo();
  }

  // Encode each channel separately.
  RTC_CHECK_EQ(num_10ms_frames_buffered_, num_10ms_frames_per_packet_);
  num_10ms_frames_buffered_ = 0;
  const size_t samples_per_channel = SamplesPerChannel();
  for (int i = 0; i < num_channels_; ++i) {
    const size_t encoded = WebRtcG722_Encode(
        encoders_[i].encoder, encoders_[i].speech_buffer.get(),
        samples_per_channel, encoders_[i].encoded_buffer.data());
    RTC_CHECK_EQ(encoded, samples_per_channel / 2);
  }

  // Interleave the encoded bytes of the different channels. Each separate
  // channel and the interleaved stream encodes two samples per byte, most
  // significant half first.
  for (size_t i = 0; i < samples_per_channel / 2; ++i) {
    for (int j = 0; j < num_channels_; ++j) {
      uint8_t two_samples = encoders_[j].encoded_buffer.data()[i];
      interleave_buffer_.data()[j] = two_samples >> 4;
      interleave_buffer_.data()[num_channels_ + j] = two_samples & 0xf;
    }
    for (int j = 0; j < num_channels_; ++j)
      encoded[i * num_channels_ + j] = interleave_buffer_.data()[2 * j] << 4 |
                                       interleave_buffer_.data()[2 * j + 1];
  }
  EncodedInfo info;
  info.encoded_bytes = samples_per_channel / 2 * num_channels_;
  info.encoded_timestamp = first_timestamp_in_buffer_;
  info.payload_type = payload_type_;
  return info;
}

void AudioEncoderG722::Reset() {
  num_10ms_frames_buffered_ = 0;
  for (int i = 0; i < num_channels_; ++i)
    RTC_CHECK_EQ(0, WebRtcG722_EncoderInit(encoders_[i].encoder));
}

AudioEncoderG722::EncoderState::EncoderState() {
  RTC_CHECK_EQ(0, WebRtcG722_CreateEncoder(&encoder));
}

AudioEncoderG722::EncoderState::~EncoderState() {
  RTC_CHECK_EQ(0, WebRtcG722_FreeEncoder(encoder));
}

size_t AudioEncoderG722::SamplesPerChannel() const {
  return kSampleRateHz / 100 * num_10ms_frames_per_packet_;
}

}  // namespace webrtc