DequantBlock()

static int fl::third_party::DequantBlock ( int32_t * inbuf, int32_t * outbuf, int num, int scale )

static

Definition at line 140 of file dqchan.hpp.

{
    int tab4[4];
    int32_t scalef, scalei, shift;
    int32_t sx, x, y;
    int32_t mask = 0;
    const int32_t *tab16, *coef;
 
    tab16 = pow43_14[scale & 0x3];
    scalef = pow14[scale & 0x3];
    scalei = MIN(scale >> 2, 31);   /* smallest input scale = -47, so smallest scalei = -12 */
 
    /* cache first 4 values */
    shift = MIN(scalei + 3, 31);
    shift = MAX(shift, 0);
    tab4[0] = 0;
    tab4[1] = tab16[1] >> shift;
    tab4[2] = tab16[2] >> shift;
    tab4[3] = tab16[3] >> shift;
 
    do {
 
        sx = *inbuf++;
        x = sx & 0x7fffffff;   /* sx = sign|mag */
 
        if (x < 4) {
 
            y = tab4[x];
 
        } else if (x < 16) {
 
            y = tab16[x];
            y = (scalei < 0) ? y << -scalei : y >> scalei;
 
        } else {
 
            if (x < 64) {
 
                y = pow43[x-16];
 
                /* fractional scale */
                y = MULSHIFT32(y, scalef);
                shift = scalei - 3;
 
            } else {
 
                /* normalize to [0x40000000, 0x7fffffff] */
                x <<= 17;
                shift = 0;
                if (x < 0x08000000)
                    x <<= 4, shift += 4;
                if (x < 0x20000000)
                    x <<= 2, shift += 2;
                if (x < 0x40000000)
                    x <<= 1, shift += 1;
 
                coef = (x < SQRTHALF) ? poly43lo : poly43hi;
 
                /* polynomial */
                y = coef[0];
                y = MULSHIFT32(y, x) + coef[1];
                y = MULSHIFT32(y, x) + coef[2];
                y = MULSHIFT32(y, x) + coef[3];
                y = MULSHIFT32(y, x) + coef[4];
                y = MULSHIFT32(y, pow2frac[shift]) << 3;
 
                /* fractional scale */
                y = MULSHIFT32(y, scalef);
                shift = scalei - pow2exp[shift];
            }
 
            /* integer scale */
            if (shift < 0) {
                shift = -shift;
                if (y > ((int32_t)0x7fffffff >> shift))
                    y = (int32_t)0x7fffffff;        /* clip */
                else
                    y <<= shift;
            } else {
                y >>= shift;
            }
        }
 
        /* sign and store */
        mask |= y;
        *outbuf++ = (sx < 0) ? -y : y;
 
    } while (--num);
 
    return mask;
}

References FL_NOEXCEPT, MAX, MIN, MULSHIFT32(), poly43hi, poly43lo, pow14, pow2exp, pow2frac, pow43, pow43_14, scale, SQRTHALF, fl::x, and fl::y.

Referenced by DequantChannel().

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