AAC音频文件添加ADTS头

/**
 * 添加ADTS头
 * 一帧AAC+7 = packetLen
 * @param packet
 * @param packetLen
 */
private void addADTStoPacket(byte[] packet, int packetLen) {
    int profile = 2; // AAC LC
    int freqIdx = 8; // 16KHz
    int chanCfg = 1; // CPE

    // fill in ADTS data
    packet[0] = (byte) 0xFF;
    packet[1] = (byte) 0xF1;
    packet[2] = (byte) (((profile - 1) << 6) + (freqIdx << 2) + (chanCfg >> 2));
    packet[3] = (byte) (((chanCfg & 3) << 6) + (packetLen >> 11));
    packet[4] = (byte) ((packetLen & 0x7FF) >> 3);
    packet[5] = (byte) (((packetLen & 7) << 5) + 0x1F);
    packet[6] = (byte) 0xFC;

}

• profile：表示使用哪个级别的AAC，如01 Low Complexity(LC) -- AAC LC
  profile的值等于 Audio Object Type的值减1.
  profile = MPEG-4 Audio Object Type - 1

sampling_frequency_index：采样率的下标

• channel_configuration：声道数，比如2表示立体声双声道