static int dv_extract_audio(uint8_t* frame, uint8_t* ppcm[4],
                            const DVprofile *sys)
{
    int size, chan, i, j, d, of, smpls, freq, quant, half_ch;
    uint16_t lc, rc;
    const uint8_t* as_pack;
    uint8_t *pcm, ipcm;
    as_pack = dv_extract_pack(frame, dv_audio_source);
    if (!as_pack)    /* No audio ? */
        return 0;
    smpls =  as_pack[1] & 0x3f;       /* samples in this frame - min. samples */
    freq  = (as_pack[4] >> 3) & 0x07; /* 0 - 48kHz, 1 - 44,1kHz, 2 - 32kHz */
    quant =  as_pack[4] & 0x07;       /* 0 - 16bit linear, 1 - 12bit nonlinear */
    if (quant > 1)
        return -1; /* unsupported quantization */
    if (freq >= FF_ARRAY_ELEMS(dv_audio_frequency))
    size = (sys->audio_min_samples[freq] + smpls) * 4; /* 2ch, 2bytes */
    half_ch = sys->difseg_size / 2;
    /* We work with 720p frames split in half, thus even frames have
     * channels 0,1 and odd 2,3. */
    ipcm = (sys->height == 720 && !(frame[1] & 0x0C)) ? 2 : 0;
    /* for each DIF channel */
    for (chan = 0; chan < sys->n_difchan; chan++) {
        av_assert0(ipcm<4);
        pcm = ppcm[ipcm++];
        if (!pcm)
            break;
        /* for each DIF segment */
        for (i = 0; i < sys->difseg_size; i++) {
            frame += 6 * 80; /* skip DIF segment header */
            if (quant == 1 && i == half_ch) {
                /* next stereo channel (12bit mode only) */
                av_assert0(ipcm<4);
                pcm = ppcm[ipcm++];
                if (!pcm)
                    break;
            /* for each AV sequence */
            for (j = 0; j < 9; j++) {
                for (d = 8; d < 80; d += 2) {
                    if (quant == 0) {  /* 16bit quantization */
                        of = sys->audio_shuffle[i][j] + (d - 8) / 2 * sys->audio_stride;
                        if (of*2 >= size)
                            continue;
                        pcm[of*2]   = frame[d+1]; // FIXME: maybe we have to admit
                        pcm[of*2+1] = frame[d];   //        that DV is a big-endian PCM
                        if (pcm[of*2+1] == 0x80 && pcm[of*2] == 0x00)
                            pcm[of*2+1] = 0;
                    } else {           /* 12bit quantization */
                        lc = ((uint16_t)frame[d]   << 4) |
                             ((uint16_t)frame[d+2] >> 4);
                        rc = ((uint16_t)frame[d+1] << 4) |
                             ((uint16_t)frame[d+2] & 0x0f);
                        lc = (lc == 0x800 ? 0 : dv_audio_12to16(lc));
                        rc = (rc == 0x800 ? 0 : dv_audio_12to16(rc));
                        of = sys->audio_shuffle[i%half_ch][j] + (d - 8) / 3 * sys->audio_stride;
                        if (of*2 >= size)
                            continue;
                        pcm[of*2]   = lc & 0xff; // FIXME: maybe we have to admit
                        pcm[of*2+1] = lc >> 8;   //        that DV is a big-endian PCM
                        of = sys->audio_shuffle[i%half_ch+half_ch][j] +
                            (d - 8) / 3 * sys->audio_stride;
                        pcm[of*2]   = rc & 0xff; // FIXME: maybe we have to admit
                        pcm[of*2+1] = rc >> 8;   //        that DV is a big-endian PCM
                        ++d;
                frame += 16 * 80; /* 15 Video DIFs + 1 Audio DIF */
    return size;