vdec_idct.c

vlc stand 0.1.99 ist sehr einfach

         * With typical images and quantization tables, half or more of the
         * row DCT calculations can be simplified this way.
         */

        register int * idataptr = (int*)dataptr;
        d0 = dataptr[0];
        d1 = dataptr[1];
        if ( (d1 == 0) && ((idataptr[1] | idataptr[2] | idataptr[3]) == 0) )
        {
      /* AC terms all zero */
            if (d0)
            {
      /* Compute a 32 bit value to assign. */
                dctelem_t dcval = (dctelem_t) (d0 << PASS1_BITS);
                register int v = (dcval & 0xffff) | (dcval << 16);

                idataptr[0] = v;
                idataptr[1] = v;
                idataptr[2] = v;
                idataptr[3] = v;
            }

            dataptr += DCTSIZE; /* advance pointer to next row */
            continue;
        }
        d2 = dataptr[2];
        d3 = dataptr[3];
        d4 = dataptr[4];
        d5 = dataptr[5];
        d6 = dataptr[6];
        d7 = dataptr[7];

    /* Even part: reverse the even part of the forward DCT. */
    /* The rotator is sqrt(2)*c(-6). */
        if (d6)
        {
            if (d4)
            {
                if (d2)
                {
                    if (d0)
                    {
            /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */
                        z1 = MULTIPLY(d2 + d6, FIX(0.541196100));
                        tmp2 = z1 + MULTIPLY(d6, - FIX(1.847759065));
                        tmp3 = z1 + MULTIPLY(d2, FIX(0.765366865));

                        tmp0 = (d0 + d4) << CONST_BITS;
                        tmp1 = (d0 - d4) << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp1 + tmp2;
                        tmp12 = tmp1 - tmp2;
                    }
                    else
                    {
                    /* d0 == 0, d2 != 0, d4 != 0, d6 != 0 */
                        z1 = MULTIPLY(d2 + d6, FIX(0.541196100));
                        tmp2 = z1 + MULTIPLY(d6, - FIX(1.847759065));
                        tmp3 = z1 + MULTIPLY(d2, FIX(0.765366865));

                        tmp0 = d4 << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp2 - tmp0;
                        tmp12 = -(tmp0 + tmp2);
                        }
                }
                else
                {
                    if (d0)
                    {
            /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */
                        tmp2 = MULTIPLY(d6, - FIX2(1.306562965));
                        tmp3 = MULTIPLY(d6, FIX(0.541196100));

                        tmp0 = (d0 + d4) << CONST_BITS;
                        tmp1 = (d0 - d4) << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp1 + tmp2;
                        tmp12 = tmp1 - tmp2;
                        }
                    else
                    {
                    /* d0 == 0, d2 == 0, d4 != 0, d6 != 0 */
                        tmp2 = MULTIPLY(d6, - FIX2(1.306562965));
                        tmp3 = MULTIPLY(d6, FIX(0.541196100));

                        tmp0 = d4 << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp2 - tmp0;
                        tmp12 = -(tmp0 + tmp2);
                        }
                }
            }
            else
            {
                if (d2)
                {
                    if (d0)
                    {
            /* d0 != 0, d2 != 0, d4 == 0, d6 != 0 */
                        z1 = MULTIPLY(d2 + d6, FIX(0.541196100));
                        tmp2 = z1 + MULTIPLY(d6, - FIX(1.847759065));
                        tmp3 = z1 + MULTIPLY(d2, FIX(0.765366865));

                        tmp0 = d0 << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp0 + tmp2;
                        tmp12 = tmp0 - tmp2;
                    }
                    else
                    {
                    /* d0 == 0, d2 != 0, d4 == 0, d6 != 0 */
                        z1 = MULTIPLY(d2 + d6, FIX(0.541196100));
                        tmp2 = z1 + MULTIPLY(d6, - FIX(1.847759065));
                        tmp3 = z1 + MULTIPLY(d2, FIX(0.765366865));

                        tmp10 = tmp3;
                        tmp13 = -tmp3;
                        tmp11 = tmp2;
                        tmp12 = -tmp2;
                            }
                }
                else
                {
                    if (d0)
                    {
            /* d0 != 0, d2 == 0, d4 == 0, d6 != 0 */
                        tmp2 = MULTIPLY(d6, - FIX2(1.306562965));
                        tmp3 = MULTIPLY(d6, FIX(0.541196100));

                        tmp0 = d0 << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp0 + tmp2;
                        tmp12 = tmp0 - tmp2;
                    }
                    else
                    {
            /* d0 == 0, d2 == 0, d4 == 0, d6 != 0 */
                        tmp2 = MULTIPLY(d6, - FIX2(1.306562965));
                        tmp3 = MULTIPLY(d6, FIX(0.541196100));

                        tmp10 = tmp3;
                        tmp13 = -tmp3;
                        tmp11 = tmp2;
                        tmp12 = -tmp2;
                    }
                }
            }
        }
        else
        {
            if (d4)
            {
                if (d2)
                {
                    if (d0)
                    {
                    /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */
                        tmp2 = MULTIPLY(d2, FIX(0.541196100));
                        tmp3 = MULTIPLY(d2, (FIX(1.306562965) + .5));

                        tmp0 = (d0 + d4) << CONST_BITS;
                        tmp1 = (d0 - d4) << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp1 + tmp2;
                        tmp12 = tmp1 - tmp2;
                    }
                    else
                    {
            /* d0 == 0, d2 != 0, d4 != 0, d6 == 0 */
                        tmp2 = MULTIPLY(d2, FIX(0.541196100));
                        tmp3 = MULTIPLY(d2, (FIX(1.306562965) + .5));

                        tmp0 = d4 << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp2 - tmp0;
                        tmp12 = -(tmp0 + tmp2);
                    }
                }
                else
                {
                    if (d0)
                    {
            /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
                        tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
                        tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
                    }
                    else
                    {
            /* d0 == 0, d2 == 0, d4 != 0, d6 == 0 */
                        tmp10 = tmp13 = d4 << CONST_BITS;
                        tmp11 = tmp12 = -tmp10;
                    }
                }
            }
            else
            {
                if (d2)
                {
                    if (d0)
                    {
            /* d0 != 0, d2 != 0, d4 == 0, d6 == 0 */
                        tmp2 = MULTIPLY(d2, FIX(0.541196100));
                        tmp3 = MULTIPLY(d2, (FIX(1.306562965) + .5));

                        tmp0 = d0 << CONST_BITS;

                        tmp10 = tmp0 + tmp3;
                        tmp13 = tmp0 - tmp3;
                        tmp11 = tmp0 + tmp2;
                        tmp12 = tmp0 - tmp2;
                    }
                    else
                    {
            /* d0 == 0, d2 != 0, d4 == 0, d6 == 0 */
                        tmp2 = MULTIPLY(d2, FIX(0.541196100));
                        tmp3 = MULTIPLY(d2, (FIX(1.306562965) + .5));

                        tmp10 = tmp3;
                        tmp13 = -tmp3;
                        tmp11 = tmp2;
                        tmp12 = -tmp2;
                    }
                }
                else
                {
                    if (d0)
                    {
            /* d0 != 0, d2 == 0, d4 == 0, d6 == 0 */
                        tmp10 = tmp13 = tmp11 = tmp12 = d0 << CONST_BITS;
                    }
                    else
                    {
            /* d0 == 0, d2 == 0, d4 == 0, d6 == 0 */
                        tmp10 = tmp13 = tmp11 = tmp12 = 0;
                    }
                }
            }
        }


    /* Odd part per figure 8; the matrix is unitary and hence its
     * transpose is its inverse.  i0..i3 are y7,y5,y3,y1 respectively.
     */

        if (d7)
            {
            if (d5)
            {
                if (d3)
                {
                    if (d1)
                    {
            /* d1 != 0, d3 != 0, d5 != 0, d7 != 0 */
                        z1 = d7 + d1;
                        z2 = d5 + d3;
                        z3 = d7 + d3;
                        z4 = d5 + d1;
                        z5 = MULTIPLY(z3 + z4, FIX(1.175875602));

                        tmp0 = MULTIPLY(d7, FIX(0.298631336));
                        tmp1 = MULTIPLY(d5, FIX(2.053119869));
                        tmp2 = MULTIPLY(d3, FIX(3.072711026));
                        tmp3 = MULTIPLY(d1, FIX(1.501321110));
                        z1 = MULTIPLY(z1, - FIX(0.899976223));
                        z2 = MULTIPLY(z2, - FIX(2.562915447));
                        z3 = MULTIPLY(z3, - FIX(1.961570560));
                        z4 = MULTIPLY(z4, - FIX(0.390180644));

                        z3 += z5;
                        z4 += z5;

                        tmp0 += z1 + z3;
                        tmp1 += z2 + z4;
                        tmp2 += z2 + z3;
                        tmp3 += z1 + z4;
                    }
                    else
                    {
            /* d1 == 0, d3 != 0, d5 != 0, d7 != 0 */
                        z2 = d5 + d3;
                        z3 = d7 + d3;
                        z5 = MULTIPLY(z3 + d5, FIX(1.175875602));

                        tmp0 = MULTIPLY(d7, FIX(0.298631336));
                        tmp1 = MULTIPLY(d5, FIX(2.053119869));
                        tmp2 = MULTIPLY(d3, FIX(3.072711026));
                        z1 = MULTIPLY(d7, - FIX(0.899976223));
                        z2 = MULTIPLY(z2, - FIX(2.562915447));
                        z3 = MULTIPLY(z3, - FIX(1.961570560));
                        z4 = MULTIPLY(d5, - FIX(0.390180644));

                        z3 += z5;
                        z4 += z5;

                        tmp0 += z1 + z3;
                        tmp1 += z2 + z4;
                        tmp2 += z2 + z3;
                        tmp3 = z1 + z4;
                        }
                    }
                else
                {
                    if (d1)
                    {
            /* d1 != 0, d3 == 0, d5 != 0, d7 != 0 */
                        z1 = d7 + d1;
                        z4 = d5 + d1;
                        z5 = MULTIPLY(d7 + z4, FIX(1.175875602));

                        tmp0 = MULTIPLY(d7, FIX(0.298631336));
                        tmp1 = MULTIPLY(d5, FIX(2.053119869));
                        tmp3 = MULTIPLY(d1, FIX(1.501321110));
                        z1 = MULTIPLY(z1, - FIX(0.899976223));
                        z2 = MULTIPLY(d5, - FIX(2.562915447));
                        z3 = MULTIPLY(d7, - FIX(1.961570560));
                        z4 = MULTIPLY(z4, - FIX(0.390180644));

                        z3 += z5;
                        z4 += z5;

                        tmp0 += z1 + z3;
                        tmp1 += z2 + z4;
                        tmp2 = z2 + z3;
                        tmp3 += z1 + z4;
                    }
                    else
                    {
            /* d1 == 0, d3 == 0, d5 != 0, d7 != 0 */
                        z5 = MULTIPLY(d7 + d5, FIX(1.175875602));

                        tmp0 = MULTIPLY(d7, - FIX2(0.601344887));
                        tmp1 = MULTIPLY(d5, - FIX2(0.509795578));
                        z1 = MULTIPLY(d7, - FIX(0.899976223));
                        z3 = MULTIPLY(d7, - FIX(1.961570560));
                        z2 = MULTIPLY(d5, - FIX(2.562915447));
                        z4 = MULTIPLY(d5, - FIX(0.390180644));

                        z3 += z5;
                        z4 += z5;

                        tmp0 += z3;
                        tmp1 += z4;
                        tmp2 = z2 + z3;
                        tmp3 = z1 + z4;
                    }
                }
            }
            else
            {
                if (d3)
                {
                    if (d1)
                    {
            /* d1 != 0, d3 != 0, d5 == 0, d7 != 0 */
                        z1 = d7 + d1;
                        z3 = d7 + d3;
                        z5 = MULTIPLY(z3 + d1, FIX(1.175875602));

                        tmp0 = MULTIPLY(d7, FIX(0.298631336));
                        tmp2 = MULTIPLY(d3, FIX(3.072711026));
                        tmp3 = MULTIPLY(d1, FIX(1.501321110));
                        z1 = MULTIPLY(z1, - FIX(0.899976223));
                        z2 = MULTIPLY(d3, - FIX(2.562915447));
                        z3 = MULTIPLY(z3, - FIX(1.961570560));
                        z4 = MULTIPLY(d1, - FIX(0.390180644));

                        z3 += z5;
                        z4 += z5;