xref: /utopia/UTPA2-700.0.x/modules/ojpd_vdec_v1/api/jpeg/cmodel/src/jidctint.c (revision 53ee8cc121a030b8d368113ac3e966b4705770ef)

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/*
 * jidctint.c
 *
 * Copyright (C) 1991-1998, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains a slow-but-accurate integer implementation of the
 * inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
 * must also perform dequantization of the input coefficients.
 *
 * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
 * on each row (or vice versa, but it's more convenient to emit a row at
 * a time).  Direct algorithms are also available, but they are much more
 * complex and seem not to be any faster when reduced to code.
 *
 * This implementation is based on an algorithm described in
 *   C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
 *   Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
 *   Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
 * The primary algorithm described there uses 11 multiplies and 29 adds.
 * We use their alternate method with 12 multiplies and 32 adds.
 * The advantage of this method is that no data path contains more than one
 * multiplication; this allows a very simple and accurate implementation in
 * scaled fixed-point arithmetic, with a minimal number of shifts.
 */

#include "jpegmain.h"
#include "apiJPEG.h"
///#define JPEG_INTERNALS
///#include "jinclude.h"
///#include "jpeglib.h"
///#include "jdct.h"        /* Private declarations for DCT subsystem */

#if 1///def DCT_ISLOW_SUPPORTED


/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#define DCTSIZE 8
#define BITS_IN_JSAMPLE 8


#if DCTSIZE != 8
Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
#endif


/*
 * The poop on this scaling stuff is as follows:
 *
 * Each 1-D IDCT step produces outputs which are a factor of sqrt(N)
 * larger than the true IDCT outputs.  The final outputs are therefore
 * a factor of N larger than desired; since N=8 this can be cured by
 * a simple right shift at the end of the algorithm.  The advantage of
 * this arrangement is that we save two multiplications per 1-D IDCT,
 * because the y0 and y4 inputs need not be divided by sqrt(N).
 *
 * We have to do addition and subtraction of the integer inputs, which
 * is no problem, and multiplication by fractional constants, which is
 * a problem to do in integer arithmetic.  We multiply all the constants
 * by CONST_SCALE and convert them to integer constants (thus retaining
 * CONST_BITS bits of precision in the constants).  After doing a
 * multiplication we have to divide the product by CONST_SCALE, with proper
 * rounding, to produce the correct output.  This division can be done
 * cheaply as a right shift of CONST_BITS bits.  We postpone shifting
 * as long as possible so that partial sums can be added together with
 * full fractional precision.
 *
 * The outputs of the first pass are scaled up by PASS1_BITS bits so that
 * they are represented to better-than-integral precision.  These outputs
 * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
 * with the recommended scaling.  (To scale up 12-bit sample data further, an
 * intermediate INT32 array would be needed.)
 *
 * To avoid overflow of the 32-bit intermediate results in pass 2, we must
 * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26.  Error analysis
 * shows that the values given below are the most effective.
 */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  13
#define PASS1_BITS  2
#else
#define CONST_BITS  13
#define PASS1_BITS  1       /* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 13
#define FIX_0_298631336  ((INT32)  2446)    /* FIX(0.298631336) */
#define FIX_0_390180644  ((INT32)  3196)    /* FIX(0.390180644) */
#define FIX_0_541196100  ((INT32)  4433)    /* FIX(0.541196100) */
#define FIX_0_765366865  ((INT32)  6270)    /* FIX(0.765366865) */
#define FIX_0_899976223  ((INT32)  7373)    /* FIX(0.899976223) */
#define FIX_1_175875602  ((INT32)  9633)    /* FIX(1.175875602) */
#define FIX_1_501321110  ((INT32)  12299)   /* FIX(1.501321110) */
#define FIX_1_847759065  ((INT32)  15137)   /* FIX(1.847759065) */
#define FIX_1_961570560  ((INT32)  16069)   /* FIX(1.961570560) */
#define FIX_2_053119869  ((INT32)  16819)   /* FIX(2.053119869) */
#define FIX_2_562915447  ((INT32)  20995)   /* FIX(2.562915447) */
#define FIX_3_072711026  ((INT32)  25172)   /* FIX(3.072711026) */
#else
#define FIX_0_298631336  FIX(0.298631336)
#define FIX_0_390180644  FIX(0.390180644)
#define FIX_0_541196100  FIX(0.541196100)
#define FIX_0_765366865  FIX(0.765366865)
#define FIX_0_899976223  FIX(0.899976223)
#define FIX_1_175875602  FIX(1.175875602)
#define FIX_1_501321110  FIX(1.501321110)
#define FIX_1_847759065  FIX(1.847759065)
#define FIX_1_961570560  FIX(1.961570560)
#define FIX_2_053119869  FIX(2.053119869)
#define FIX_2_562915447  FIX(2.562915447)
#define FIX_3_072711026  FIX(3.072711026)
#endif


/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */

/*
#if 0 ///BITS_IN_JSAMPLE == 8
#define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
#else
#define MULTIPLY(var,const)  ((var) * (const))
#endif
*/
#define MULTIPLY(var,cnst)  ((var) * (cnst))

/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */

#define ISLOW_MULT_TYPE int
#define DEQUANTIZE(coef,quantval)  (coef) //(((ISLOW_MULT_TYPE) (coef)) )  ///(((ISLOW_MULT_TYPE) (coef)) * (quantval))

//#define DESCALE(x,n)  ( ( (x) + (1 << ((n)-1)) ) >> n)
#define SCALEDONE ((int32) 1)
#define DESCALE(x,n)  (((x) + (SCALEDONE << ((n)-1))) >> (n))

/*
 * Perform dequantization and inverse DCT on one block of coefficients.
 */

///GLOBAL(void)
///jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info * compptr,
///      JCOEFPTR coef_block,
///      JSAMPARRAY output_buf, JDIMENSION output_col)
#define clamp(i) if (i & 0xFF00) i = (((~i) >> 15) & 0xFF);
void jpeg_idct_islow( JPEG_BLOCK_TYPE *data, U8 *Pdst_ptr )
{
    #define INT32   S32
    #define DCTSIZE2 64
    #define DCTSIZE 8

    INT32 tmp0, tmp1, tmp2, tmp3;
    INT32 tmp10, tmp11, tmp12, tmp13;
    INT32 z1, z2, z3, z4, z5;
    ///JCOEFPTR inptr;
    register JPEG_BLOCK_TYPE *inptr;
    ///ISLOW_MULT_TYPE *quantptr;
    U8 *outptr = Pdst_ptr;
    ///JSAMPLE *range_limit = IDCT_range_limit(cinfo);
    int ctr;
    JPEG_BLOCK_TYPE workspace[DCTSIZE2]; /* buffers data between passes */
    JPEG_BLOCK_TYPE *wsptr;
    ///SHIFT_TEMPS
    S16 i;
//printf("Jidctint::jpeg_idct_islow\n");
    /* Pass 1: process columns from input, store into work array. */
    /* Note results are scaled up by sqrt(8) compared to a true IDCT; */
    /* furthermore, we scale the results by 2**PASS1_BITS. */

    inptr = data;
    ///quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
    wsptr = workspace;
    for ( ctr = DCTSIZE; ctr > 0; ctr-- )
    {
        /* Due to quantization, we will usually find that many of the input
         * coefficients are zero, especially the AC terms.  We can exploit this
         * by short-circuiting the IDCT calculation for any column in which all
         * the AC terms are zero.  In that case each output is equal to the
         * DC coefficient (with scale factor as needed).
         * With typical images and quantization tables, half or more of the
         * column DCT calculations can be simplified this way.
         */

        if ( ( inptr[DCTSIZE * 1] | inptr[DCTSIZE * 2] | inptr[DCTSIZE * 3] | inptr[DCTSIZE * 4] | inptr[DCTSIZE * 5] | inptr[DCTSIZE * 6] | inptr[DCTSIZE * 7] ) == 0 )
        {
            /* AC terms all zero */
            int dcval = DEQUANTIZE( inptr[DCTSIZE*0], quantptr[DCTSIZE*0] ) << PASS1_BITS;

            wsptr[DCTSIZE * 0] = dcval;
            wsptr[DCTSIZE * 1] = dcval;
            wsptr[DCTSIZE * 2] = dcval;
            wsptr[DCTSIZE * 3] = dcval;
            wsptr[DCTSIZE * 4] = dcval;
            wsptr[DCTSIZE * 5] = dcval;
            wsptr[DCTSIZE * 6] = dcval;
            wsptr[DCTSIZE * 7] = dcval;

            inptr++;            /* advance pointers to next column */
            //quantptr++;
            wsptr++;
            continue;
        }

        /* Even part: reverse the even part of the forward DCT. */
        /* The rotator is sqrt(2)*c(-6). */

        z2 = DEQUANTIZE( inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2] );
        z3 = DEQUANTIZE( inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6] );

        z1 = MULTIPLY( z2 + z3, FIX_0_541196100 );
        tmp2 = z1 + MULTIPLY( z3, -FIX_1_847759065 );
        tmp3 = z1 + MULTIPLY( z2, FIX_0_765366865 );

        z2 = DEQUANTIZE( inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0] );
        z3 = DEQUANTIZE( inptr[DCTSIZE * 4], quantptr[DCTSIZE * 4] );

        tmp0 = ( z2 + z3 ) << CONST_BITS;
        tmp1 = ( z2 - z3 ) << CONST_BITS;

        tmp10 = tmp0 + tmp3;
        tmp13 = tmp0 - tmp3;
        tmp11 = tmp1 + tmp2;
        tmp12 = tmp1 - tmp2;

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

        tmp0 = DEQUANTIZE( inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7] );
        tmp1 = DEQUANTIZE( inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5] );
        tmp2 = DEQUANTIZE( inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3] );
        tmp3 = DEQUANTIZE( inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1] );

        z1 = tmp0 + tmp3;
        z2 = tmp1 + tmp2;
        z3 = tmp0 + tmp2;
        z4 = tmp1 + tmp3;
        z5 = MULTIPLY( z3 + z4, FIX_1_175875602 ); /* sqrt(2) * c3 */

        tmp0 = MULTIPLY( tmp0, FIX_0_298631336 ); /* sqrt(2) * (-c1+c3+c5-c7) */
        tmp1 = MULTIPLY( tmp1, FIX_2_053119869 ); /* sqrt(2) * ( c1+c3-c5+c7) */
        tmp2 = MULTIPLY( tmp2, FIX_3_072711026 ); /* sqrt(2) * ( c1+c3+c5-c7) */
        tmp3 = MULTIPLY( tmp3, FIX_1_501321110 ); /* sqrt(2) * ( c1+c3-c5-c7) */
        z1 = MULTIPLY( z1, -FIX_0_899976223 ); /* sqrt(2) * (c7-c3) */
        z2 = MULTIPLY( z2, -FIX_2_562915447 ); /* sqrt(2) * (-c1-c3) */
        z3 = MULTIPLY( z3, -FIX_1_961570560 ); /* sqrt(2) * (-c3-c5) */
        z4 = MULTIPLY( z4, -FIX_0_390180644 ); /* sqrt(2) * (c5-c3) */

        z3 += z5;
        z4 += z5;

        tmp0 += z1 + z3;
        tmp1 += z2 + z4;
        tmp2 += z2 + z3;
        tmp3 += z1 + z4;

        /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */

        wsptr[DCTSIZE * 0] = ( int )DESCALE( tmp10 + tmp3, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 7] = ( int )DESCALE( tmp10 - tmp3, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 1] = ( int )DESCALE( tmp11 + tmp2, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 6] = ( int )DESCALE( tmp11 - tmp2, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 2] = ( int )DESCALE( tmp12 + tmp1, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 5] = ( int )DESCALE( tmp12 - tmp1, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 3] = ( int )DESCALE( tmp13 + tmp0, CONST_BITS - PASS1_BITS );
        wsptr[DCTSIZE * 4] = ( int )DESCALE( tmp13 - tmp0, CONST_BITS - PASS1_BITS );

        inptr++;            /* advance pointers to next column */
        //quantptr++;
        wsptr++;
    }

    /* Pass 2: process rows from work array, store into output array. */
    /* Note that we must descale the results by a factor of 8 == 2**3, */
    /* and also undo the PASS1_BITS scaling. */

    wsptr = workspace;
    for ( ctr = 0; ctr < DCTSIZE; ctr++ )
    {
        ///outptr = output_buf[ctr] + output_col;
        /* Rows of zeroes can be exploited in the same way as we did with columns.
         * However, the column calculation has created many nonzero AC terms, so
         * the simplification applies less often (typically 5% to 10% of the time).
         * On machines with very fast multiplication, it's possible that the
         * test takes more time than it's worth.  In that case this section
         * may be commented out.
         */

        #if 1///ndef NO_ZERO_ROW_TEST
        if ( ( wsptr[1] | wsptr[2] | wsptr[3] | wsptr[4] | wsptr[5] | wsptr[6] | wsptr[7] ) == 0 )
        {
            /* AC terms all zero */
            int dcval = ( int )DESCALE( ( INT32 )wsptr[DCTSIZE*0], PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3) & RANGE_MASK];
            clamp( dcval )
            outptr[0] = dcval;
            outptr[1] = dcval;
            outptr[2] = dcval;
            outptr[3] = dcval;
            outptr[4] = dcval;
            outptr[5] = dcval;
            outptr[6] = dcval;
            outptr[7] = dcval;

            wsptr += DCTSIZE;       /* advance pointer to next row */
            outptr += DCTSIZE;
            continue;
        }
        #endif

        /* Even part: reverse the even part of the forward DCT. */
        /* The rotator is sqrt(2)*c(-6). */

        z2 = ( INT32 )wsptr[2];
        z3 = ( INT32 )wsptr[6];

        z1 = MULTIPLY( z2 + z3, FIX_0_541196100 );
        tmp2 = z1 + MULTIPLY( z3, -FIX_1_847759065 );
        tmp3 = z1 + MULTIPLY( z2, FIX_0_765366865 );

        tmp0 = ( ( INT32 )wsptr[0] + ( INT32 )wsptr[4] ) << CONST_BITS;
        tmp1 = ( ( INT32 )wsptr[0] - ( INT32 )wsptr[4] ) << CONST_BITS;

        tmp10 = tmp0 + tmp3;
        tmp13 = tmp0 - tmp3;
        tmp11 = tmp1 + tmp2;
        tmp12 = tmp1 - tmp2;

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

        tmp0 = ( INT32 )wsptr[7];
        tmp1 = ( INT32 )wsptr[5];
        tmp2 = ( INT32 )wsptr[3];
        tmp3 = ( INT32 )wsptr[1];

        z1 = tmp0 + tmp3;
        z2 = tmp1 + tmp2;
        z3 = tmp0 + tmp2;
        z4 = tmp1 + tmp3;
        z5 = MULTIPLY( z3 + z4, FIX_1_175875602 ); /* sqrt(2) * c3 */

        tmp0 = MULTIPLY( tmp0, FIX_0_298631336 ); /* sqrt(2) * (-c1+c3+c5-c7) */
        tmp1 = MULTIPLY( tmp1, FIX_2_053119869 ); /* sqrt(2) * ( c1+c3-c5+c7) */
        tmp2 = MULTIPLY( tmp2, FIX_3_072711026 ); /* sqrt(2) * ( c1+c3+c5-c7) */
        tmp3 = MULTIPLY( tmp3, FIX_1_501321110 ); /* sqrt(2) * ( c1+c3-c5-c7) */
        z1 = MULTIPLY( z1, -FIX_0_899976223 ); /* sqrt(2) * (c7-c3) */
        z2 = MULTIPLY( z2, -FIX_2_562915447 ); /* sqrt(2) * (-c1-c3) */
        z3 = MULTIPLY( z3, -FIX_1_961570560 ); /* sqrt(2) * (-c3-c5) */
        z4 = MULTIPLY( z4, -FIX_0_390180644 ); /* sqrt(2) * (c5-c3) */

        z3 += z5;
        z4 += z5;

        tmp0 += z1 + z3;
        tmp1 += z2 + z4;
        tmp2 += z2 + z3;
        tmp3 += z1 + z4;

        /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
        i = ( int )DESCALE( tmp10 + tmp3, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp10 + tmp3, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[0] = ( U8 )i;

        i = ( int )DESCALE( tmp10 - tmp3, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp10 - tmp3, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[7] = ( U8 )i;
        i = ( int )DESCALE( tmp11 + tmp2, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp11 + tmp2, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[1] = ( U8 )i;
        i = ( int )DESCALE( tmp11 - tmp2, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp11 - tmp2, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[6] = ( U8 )i;
        i = ( int )DESCALE( tmp12 + tmp1, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp12 + tmp1, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[2] = ( U8 )i;
        i = ( int )DESCALE( tmp12 - tmp1, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp12 - tmp1, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[5] = ( U8 )i;
        i = ( int )DESCALE( tmp13 + tmp0, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp13 + tmp0, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[3] = ( U8 )i;
        i = ( int )DESCALE( tmp13 - tmp0, CONST_BITS + PASS1_BITS + 3 ) + 128; ///range_limit[(int) DESCALE(tmp13 - tmp0, CONST_BITS+PASS1_BITS+3) & RANGE_MASK];
        clamp( i )
        outptr[4] = ( U8 )i;

        wsptr += DCTSIZE;       /* advance pointer to next row */
        outptr += DCTSIZE;
    }
}


#endif /* DCT_ISLOW_SUPPORTED */