swscale.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

            {
                double d= FFABS(xx - xDstInSrc)/filterSizeInSrc*sizeFactor;
                double coeff;
                if (flags & SWS_BICUBIC)
                {
                    double B= param[0] != SWS_PARAM_DEFAULT ? param[0] : 0.0;
                    double C= param[1] != SWS_PARAM_DEFAULT ? param[1] : 0.6;

                    if (d<1.0)
                        coeff = (12-9*B-6*C)*d*d*d + (-18+12*B+6*C)*d*d + 6-2*B;
                    else if (d<2.0)
                        coeff = (-B-6*C)*d*d*d + (6*B+30*C)*d*d + (-12*B-48*C)*d +8*B+24*C;
                    else
                        coeff=0.0;
                }
/*                else if (flags & SWS_X)
                {
                    double p= param ? param*0.01 : 0.3;
                    coeff = d ? sin(d*PI)/(d*PI) : 1.0;
                    coeff*= pow(2.0, - p*d*d);
                }*/
                else if (flags & SWS_X)
                {
                    double A= param[0] != SWS_PARAM_DEFAULT ? param[0] : 1.0;

                    if (d<1.0)
                        coeff = cos(d*PI);
                    else
                        coeff=-1.0;
                    if (coeff<0.0)      coeff= -pow(-coeff, A);
                    else                coeff=  pow( coeff, A);
                    coeff= coeff*0.5 + 0.5;
                }
                else if (flags & SWS_AREA)
                {
                    double srcPixelSize= 1.0/xInc1;
                    if      (d + srcPixelSize/2 < 0.5) coeff= 1.0;
                    else if (d - srcPixelSize/2 < 0.5) coeff= (0.5-d)/srcPixelSize + 0.5;
                    else coeff=0.0;
                }
                else if (flags & SWS_GAUSS)
                {
                    double p= param[0] != SWS_PARAM_DEFAULT ? param[0] : 3.0;
                    coeff = pow(2.0, - p*d*d);
                }
                else if (flags & SWS_SINC)
                {
                    coeff = d ? sin(d*PI)/(d*PI) : 1.0;
                }
                else if (flags & SWS_LANCZOS)
                {
                    double p= param[0] != SWS_PARAM_DEFAULT ? param[0] : 3.0;
                    coeff = d ? sin(d*PI)*sin(d*PI/p)/(d*d*PI*PI/p) : 1.0;
                    if (d>p) coeff=0;
                }
                else if (flags & SWS_BILINEAR)
                {
                    coeff= 1.0 - d;
                    if (coeff<0) coeff=0;
                }
                else if (flags & SWS_SPLINE)
                {
                    double p=-2.196152422706632;
                    coeff = getSplineCoeff(1.0, 0.0, p, -p-1.0, d);
                }
                else {
                    coeff= 0.0; //GCC warning killer
                    ASSERT(0)
                }

                filter[i*filterSize + j]= coeff;
                xx++;
            }
            xDstInSrc+= xInc1;
        }
    }

    /* apply src & dst Filter to filter -> filter2
       av_free(filter);
    */
    ASSERT(filterSize>0)
    filter2Size= filterSize;
    if (srcFilter) filter2Size+= srcFilter->length - 1;
    if (dstFilter) filter2Size+= dstFilter->length - 1;
    ASSERT(filter2Size>0)
    filter2= av_malloc(filter2Size*dstW*sizeof(double));

    for (i=0; i<dstW; i++)
    {
        int j;
        SwsVector scaleFilter;
        SwsVector *outVec;

        scaleFilter.coeff= filter + i*filterSize;
        scaleFilter.length= filterSize;

        if (srcFilter) outVec= sws_getConvVec(srcFilter, &scaleFilter);
        else           outVec= &scaleFilter;

        ASSERT(outVec->length == filter2Size)
        //FIXME dstFilter

        for (j=0; j<outVec->length; j++)
        {
            filter2[i*filter2Size + j]= outVec->coeff[j];
        }

        (*filterPos)[i]+= (filterSize-1)/2 - (filter2Size-1)/2;

        if (outVec != &scaleFilter) sws_freeVec(outVec);
    }
    av_free(filter); filter=NULL;

    /* try to reduce the filter-size (step1 find size and shift left) */
    // Assume it is near normalized (*0.5 or *2.0 is OK but * 0.001 is not).
    minFilterSize= 0;
    for (i=dstW-1; i>=0; i--)
    {
        int min= filter2Size;
        int j;
        double cutOff=0.0;

        /* get rid off near zero elements on the left by shifting left */
        for (j=0; j<filter2Size; j++)
        {
            int k;
            cutOff += FFABS(filter2[i*filter2Size]);

            if (cutOff > SWS_MAX_REDUCE_CUTOFF) break;

            /* preserve monotonicity because the core can't handle the filter otherwise */
            if (i<dstW-1 && (*filterPos)[i] >= (*filterPos)[i+1]) break;

            // Move filter coeffs left
            for (k=1; k<filter2Size; k++)
                filter2[i*filter2Size + k - 1]= filter2[i*filter2Size + k];
            filter2[i*filter2Size + k - 1]= 0.0;
            (*filterPos)[i]++;
        }

        cutOff=0.0;
        /* count near zeros on the right */
        for (j=filter2Size-1; j>0; j--)
        {
            cutOff += FFABS(filter2[i*filter2Size + j]);

            if (cutOff > SWS_MAX_REDUCE_CUTOFF) break;
            min--;
        }

        if (min>minFilterSize) minFilterSize= min;
    }

    if (flags & SWS_CPU_CAPS_ALTIVEC) {
        // we can handle the special case 4,
        // so we don't want to go to the full 8
        if (minFilterSize < 5)
            filterAlign = 4;

        // we really don't want to waste our time
        // doing useless computation, so fall-back on
        // the scalar C code for very small filter.
        // vectorizing is worth it only if you have
        // decent-sized vector.
        if (minFilterSize < 3)
            filterAlign = 1;
    }

    if (flags & SWS_CPU_CAPS_MMX) {
        // special case for unscaled vertical filtering
        if (minFilterSize == 1 && filterAlign == 2)
            filterAlign= 1;
    }

    ASSERT(minFilterSize > 0)
    filterSize= (minFilterSize +(filterAlign-1)) & (~(filterAlign-1));
    ASSERT(filterSize > 0)
    filter= av_malloc(filterSize*dstW*sizeof(double));
    if (filterSize >= MAX_FILTER_SIZE)
        return -1;
    *outFilterSize= filterSize;

    if (flags&SWS_PRINT_INFO)
        av_log(NULL, AV_LOG_VERBOSE, "SwScaler: reducing / aligning filtersize %d -> %d\n", filter2Size, filterSize);
    /* try to reduce the filter-size (step2 reduce it) */
    for (i=0; i<dstW; i++)
    {
        int j;

        for (j=0; j<filterSize; j++)
        {
            if (j>=filter2Size) filter[i*filterSize + j]= 0.0;
            else               filter[i*filterSize + j]= filter2[i*filter2Size + j];
        }
    }
    av_free(filter2); filter2=NULL;


    //FIXME try to align filterpos if possible

    //fix borders
    for (i=0; i<dstW; i++)
    {
        int j;
        if ((*filterPos)[i] < 0)
        {
            // Move filter coeffs left to compensate for filterPos
            for (j=1; j<filterSize; j++)
            {
                int left= FFMAX(j + (*filterPos)[i], 0);
                filter[i*filterSize + left] += filter[i*filterSize + j];
                filter[i*filterSize + j]=0;
            }
            (*filterPos)[i]= 0;
        }

        if ((*filterPos)[i] + filterSize > srcW)
        {
            int shift= (*filterPos)[i] + filterSize - srcW;
            // Move filter coeffs right to compensate for filterPos
            for (j=filterSize-2; j>=0; j--)
            {
                int right= FFMIN(j + shift, filterSize-1);
                filter[i*filterSize +right] += filter[i*filterSize +j];
                filter[i*filterSize +j]=0;
            }
            (*filterPos)[i]= srcW - filterSize;
        }
    }

    // Note the +1 is for the MMXscaler which reads over the end
    /* align at 16 for AltiVec (needed by hScale_altivec_real) */
    *outFilter= av_mallocz(*outFilterSize*(dstW+1)*sizeof(int16_t));

    /* Normalize & Store in outFilter */
    for (i=0; i<dstW; i++)
    {
        int j;
        double error=0;
        double sum=0;
        double scale= one;

        for (j=0; j<filterSize; j++)
        {
            sum+= filter[i*filterSize + j];
        }
        scale/= sum;
        for (j=0; j<*outFilterSize; j++)
        {
            double v= filter[i*filterSize + j]*scale + error;
            int intV= floor(v + 0.5);
            (*outFilter)[i*(*outFilterSize) + j]= intV;
            error = v - intV;
        }
    }

    (*filterPos)[dstW]= (*filterPos)[dstW-1]; // the MMX scaler will read over the end
    for (i=0; i<*outFilterSize; i++)
    {
        int j= dstW*(*outFilterSize);
        (*outFilter)[j + i]= (*outFilter)[j + i - (*outFilterSize)];
    }

    av_free(filter);
    return 0;
}

#ifdef COMPILE_MMX2
static void initMMX2HScaler(int dstW, int xInc, uint8_t *funnyCode, int16_t *filter, int32_t *filterPos, int numSplits)
{
    uint8_t *fragmentA;
    long imm8OfPShufW1A;
    long imm8OfPShufW2A;
    long fragmentLengthA;
    uint8_t *fragmentB;
    long imm8OfPShufW1B;
    long imm8OfPShufW2B;
    long fragmentLengthB;
    int fragmentPos;

    int xpos, i;

    // create an optimized horizontal scaling routine

    //code fragment

    asm volatile(
        "jmp                         9f                 \n\t"
    // Begin
        "0:                                             \n\t"
        "movq    (%%"REG_d", %%"REG_a"), %%mm3          \n\t"
        "movd    (%%"REG_c", %%"REG_S"), %%mm0          \n\t"
        "movd   1(%%"REG_c", %%"REG_S"), %%mm1          \n\t"
        "punpcklbw                %%mm7, %%mm1          \n\t"
        "punpcklbw                %%mm7, %%mm0          \n\t"
        "pshufw                   $0xFF, %%mm1, %%mm1   \n\t"
        "1:                                             \n\t"
        "pshufw                   $0xFF, %%mm0, %%mm0   \n\t"
        "2:                                             \n\t"
        "psubw                    %%mm1, %%mm0          \n\t"
        "movl   8(%%"REG_b", %%"REG_a"), %%esi          \n\t"
        "pmullw                   %%mm3, %%mm0          \n\t"
        "psllw                       $7, %%mm1          \n\t"
        "paddw                    %%mm1, %%mm0          \n\t"

        "movq                     %%mm0, (%%"REG_D", %%"REG_a") \n\t"

        "add                         $8, %%"REG_a"      \n\t"
    // End
        "9:                                             \n\t"
//        "int $3                                         \n\t"
        "lea                         0b, %0             \n\t"
        "lea                         1b, %1             \n\t"
        "lea                         2b, %2             \n\t"
        "dec                         %1                 \n\t"
        "dec                         %2                 \n\t"
        "sub                         %0, %1             \n\t"
        "sub                         %0, %2             \n\t"
        "lea                         9b, %3             \n\t"
        "sub                         %0, %3             \n\t"


        :"=r" (fragmentA), "=r" (imm8OfPShufW1A), "=r" (imm8OfPShufW2A),
        "=r" (fragmentLengthA)
    );

    asm volatile(
        "jmp                         9f                 \n\t"
    // Begin
        "0:                                             \n\t"
        "movq    (%%"REG_d", %%"REG_a"), %%mm3          \n\t"
        "movd    (%%"REG_c", %%"REG_S"), %%mm0          \n\t"
        "punpcklbw                %%mm7, %%mm0          \n\t"
        "pshufw                   $0xFF, %%mm0, %%mm1   \n\t"
        "1:                                             \n\t"
        "pshufw                   $0xFF, %%mm0, %%mm0   \n\t"
        "2:                                             \n\t"
        "psubw                    %%mm1, %%mm0          \n\t"
        "movl   8(%%"REG_b", %%"REG_a"), %%esi          \n\t"
        "pmullw                   %%mm3, %%mm0          \n\t"
        "psllw                       $7, %%mm1          \n\t"
        "paddw                    %%mm1, %%mm0          \n\t"

        "movq                     %%mm0, (%%"REG_D", %%"REG_a") \n\t"

        "add                         $8, %%"REG_a"      \n\t"
    // End
        "9:                                             \n\t"
//        "int                       $3                   \n\t"
        "lea                         0b, %0             \n\t"
        "lea                         1b, %1             \n\t"
        "lea                         2b, %2             \n\t"
        "dec                         %1                 \n\t"
        "dec                         %2                 \n\t"
        "sub                         %0, %1             \n\t"
        "sub                         %0, %2             \n\t"
        "lea                         9b, %3             \n\t"
        "sub                         %0, %3             \n\t"


        :"=r" (fragmentB), "=r" (imm8OfPShufW1B), "=r" (imm8OfPShufW2B),
        "=r" (fragmentLengthB)
    );