Adts.cpp

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "Adts.h"
#include "MediaData.h"
#include "mozilla/Array.h"
#include "mozilla/ArrayUtils.h"

namespace mozilla {

static const int kADTSHeaderSize = 7;

int8_t Adts::GetFrequencyIndex(uint32_t aSamplesPerSecond) {
  static const uint32_t freq_lookup[] = {96000, 88200, 64000, 48000, 44100,
                                         32000, 24000, 22050, 16000, 12000,
                                         11025, 8000,  7350,  0};

  int8_t i = 0;
  while (freq_lookup[i] && aSamplesPerSecond < freq_lookup[i]) {
    i++;
  }

  if (!freq_lookup[i]) {
    return -1;
  }

  return i;
}

bool Adts::ConvertSample(uint16_t aChannelCount, int8_t aFrequencyIndex,
                         int8_t aProfile, MediaRawData* aSample) {
  size_t newSize = aSample->Size() + kADTSHeaderSize;

  // ADTS header uses 13 bits for packet size.
  if (newSize >= (1 << 13) || aChannelCount > 15 || aFrequencyIndex < 0 ||
      aProfile < 1 || aProfile > 4) {
    return false;
  }

  Array<uint8_t, kADTSHeaderSize> header;
  header[0] = 0xff;
  header[1] = 0xf1;
  header[2] =
      ((aProfile - 1) << 6) + (aFrequencyIndex << 2) + (aChannelCount >> 2);
  header[3] = ((aChannelCount & 0x3) << 6) + (newSize >> 11);
  header[4] = (newSize & 0x7ff) >> 3;
  header[5] = ((newSize & 7) << 5) + 0x1f;
  header[6] = 0xfc;

  UniquePtr<MediaRawDataWriter> writer(aSample->CreateWriter());
  if (!writer->Prepend(&header[0], ArrayLength(header))) {
    return false;
  }

  if (aSample->mCrypto.IsEncrypted()) {
    if (aSample->mCrypto.mPlainSizes.Length() == 0) {
      writer->mCrypto.mPlainSizes.AppendElement(kADTSHeaderSize);
      writer->mCrypto.mEncryptedSizes.AppendElement(aSample->Size() -
                                                    kADTSHeaderSize);
    } else {
      writer->mCrypto.mPlainSizes[0] += kADTSHeaderSize;
    }
  }

  return true;
}

bool Adts::RevertSample(MediaRawData* aSample) {
  if (aSample->Size() < kADTSHeaderSize) {
    return false;
  }

  {
    const uint8_t* header = aSample->Data();
    if (header[0] != 0xff || header[1] != 0xf1 || header[6] != 0xfc) {
      // Not ADTS.
      return false;
    }
  }

  UniquePtr<MediaRawDataWriter> writer(aSample->CreateWriter());
  writer->PopFront(kADTSHeaderSize);

  if (aSample->mCrypto.IsEncrypted()) {
    if (aSample->mCrypto.mPlainSizes.Length() > 0 &&
        writer->mCrypto.mPlainSizes[0] >= kADTSHeaderSize) {
      writer->mCrypto.mPlainSizes[0] -= kADTSHeaderSize;
    }
  }

  return true;
}
}  // namespace mozilla