Function decode_coeffs

libavcodec/wmaprodec.c:919–1018

*@brief Extract the coefficients from the bitstream. *@param s codec context *@param c current channel number *@return 0 on success, < 0 in case of bitstream errors */

 *@return 0 on success, < 0 in case of bitstream errors
 */
static int decode_coeffs(WMAProDecodeCtx *s, int c)
{
    /* Integers 0..15 as single-precision floats.  The table saves a
       costly int to float conversion, and storing the values as
       integers allows fast sign-flipping. */
    static const uint32_t fval_tab[16] = {
        0x00000000, 0x3f800000, 0x40000000, 0x40400000,
        0x40800000, 0x40a00000, 0x40c00000, 0x40e00000,
        0x41000000, 0x41100000, 0x41200000, 0x41300000,
        0x41400000, 0x41500000, 0x41600000, 0x41700000,
    };
    int vlctable;
    const VLCElem *vlc;
    WMAProChannelCtx* ci = &s->channel[c];
    int rl_mode = 0;
    int cur_coeff = 0;
    int num_zeros = 0;
    const uint16_t* run;
    const float* level;

    ff_dlog(s->avctx, "decode coefficients for channel %i\n", c);

    vlctable = get_bits1(&s->gb);
    vlc = coef_vlc[vlctable];

    if (vlctable) {
        run = coef1_run;
        level = coef1_level;
    } else {
        run = coef0_run;
        level = coef0_level;
    }

    /** decode vector coefficients (consumes up to 167 bits per iteration for
      4 vector coded large values) */
    while ((s->transmit_num_vec_coeffs || !rl_mode) &&
           (cur_coeff + 3 < ci->num_vec_coeffs)) {
        uint32_t vals[4];
        int i;
        unsigned int idx;

        idx = get_vlc2(&s->gb, vec4_vlc, VLCBITS, VEC4MAXDEPTH);

        if ((int)idx < 0) {
            for (i = 0; i < 4; i += 2) {
                idx = get_vlc2(&s->gb, vec2_vlc, VLCBITS, VEC2MAXDEPTH);
                if ((int)idx < 0) {
                    uint32_t v0, v1;
                    v0 = get_vlc2(&s->gb, vec1_vlc, VLCBITS, VEC1MAXDEPTH);
                    if (v0 == HUFF_VEC1_SIZE - 1)
                        v0 += ff_wma_get_large_val(&s->gb);
                    v1 = get_vlc2(&s->gb, vec1_vlc, VLCBITS, VEC1MAXDEPTH);
                    if (v1 == HUFF_VEC1_SIZE - 1)
                        v1 += ff_wma_get_large_val(&s->gb);
                    vals[i  ] = av_float2int(v0);
                    vals[i+1] = av_float2int(v1);
                } else {
                    vals[i]   = fval_tab[idx >> 4 ];