实现：

    public static void addADTStoPacket(byte[] packet, int packetLen, int chancfg) {
        int profile = 2;  //AAC LC，MediaCodecInfo.CodecProfileLevel.AACObjectLC;
        int freqIdx = 4;  //见后面注释avpriv_mpeg4audio_sample_rates中441000对应的数组下标，来自ffmpeg源码
//        int chanCfg = 1;  //见后面注释channel_configuration，AudioFormat.CHANNEL_IN_MONO 单声道(声道数量)
        int chanCfg = chancfg;  //见后面注释channel_configuration，AudioFormat.CHANNEL_IN_MONO 单声道(声道数量)

        /*int avpriv_mpeg4audio_sample_rates[] = {96000, 88200, 64000, 48000, 44100, 32000,24000, 22050, 16000, 12000, 11025, 8000, 7350};
        channel_configuration: 表示声道数chanCfg
        0: Defined in AOT Specifc Config
        1: 1 channel: front-center
        2: 2 channels: front-left, front-right
        3: 3 channels: front-center, front-left, front-right
        4: 4 channels: front-center, front-left, front-right, back-center
        5: 5 channels: front-center, front-left, front-right, back-left, back-right
        6: 6 channels: front-center, front-left, front-right, back-left, back-right, LFE-channel
        7: 8 channels: front-center, front-left, front-right, side-left, side-right, back-left, back-right, LFE-channel
        8-15: Reserved
        */

        // fill in ADTS data
        packet[0] = (byte)0xFF;
//        packet[1] = (byte)0xF9;
        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;

    }