static int decode_subframe_lpc(ShortenContext *s, int command, int channel,
                               int residual_size, int32_t coffset)
{
    int pred_order, sum, qshift, init_sum, i, j;
    const int *coeffs;

    if (command == FN_QLPC) {
        /* read/validate prediction order */
        pred_order = get_ur_golomb_shorten(&s->gb, LPCQSIZE);
        if (pred_order > s->nwrap) {
            av_log(s->avctx, AV_LOG_ERROR, "invalid pred_order %d\n",
                   pred_order);
            return AVERROR(EINVAL);
        }
        /* read LPC coefficients */
        for (i = 0; i < pred_order; i++)
            s->coeffs[i] = get_sr_golomb_shorten(&s->gb, LPCQUANT);
        coeffs = s->coeffs;

        qshift = LPCQUANT;
    } else {
        /* fixed LPC coeffs */
        pred_order = command;
        if (pred_order >= FF_ARRAY_ELEMS(fixed_coeffs)) {
            av_log(s->avctx, AV_LOG_ERROR, "invalid pred_order %d\n",
                   pred_order);
            return AVERROR_INVALIDDATA;
        }
        coeffs     = fixed_coeffs[pred_order];
        qshift     = 0;
    }

    /* subtract offset from previous samples to use in prediction */
    if (command == FN_QLPC && coffset)
        for (i = -pred_order; i < 0; i++)
            s->decoded[channel][i] -= coffset;

    /* decode residual and do LPC prediction */
    init_sum = pred_order ? (command == FN_QLPC ? s->lpcqoffset : 0) : coffset;
    for (i = 0; i < s->blocksize; i++) {
        sum = init_sum;
        for (j = 0; j < pred_order; j++)
            sum += coeffs[j] * s->decoded[channel][i - j - 1];
        s->decoded[channel][i] = get_sr_golomb_shorten(&s->gb, residual_size) +
                                 (sum >> qshift);
    }

    /* add offset to current samples */
    if (command == FN_QLPC && coffset)
        for (i = 0; i < s->blocksize; i++)
            s->decoded[channel][i] += coffset;

    return 0;
}
Unknown