1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/libs/libjpeg/jidctred.c	Sun Nov 01 00:36:56 2015 +0200
     1.3 @@ -0,0 +1,398 @@
     1.4 +/*
     1.5 + * jidctred.c
     1.6 + *
     1.7 + * Copyright (C) 1994-1998, Thomas G. Lane.
     1.8 + * This file is part of the Independent JPEG Group's software.
     1.9 + * For conditions of distribution and use, see the accompanying README file.
    1.10 + *
    1.11 + * This file contains inverse-DCT routines that produce reduced-size output:
    1.12 + * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
    1.13 + *
    1.14 + * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
    1.15 + * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
    1.16 + * with an 8-to-4 step that produces the four averages of two adjacent outputs
    1.17 + * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
    1.18 + * These steps were derived by computing the corresponding values at the end
    1.19 + * of the normal LL&M code, then simplifying as much as possible.
    1.20 + *
    1.21 + * 1x1 is trivial: just take the DC coefficient divided by 8.
    1.22 + *
    1.23 + * See jidctint.c for additional comments.
    1.24 + */
    1.25 +
    1.26 +#define JPEG_INTERNALS
    1.27 +#include "jinclude.h"
    1.28 +#include "jpeglib.h"
    1.29 +#include "jdct.h"		/* Private declarations for DCT subsystem */
    1.30 +
    1.31 +#ifdef IDCT_SCALING_SUPPORTED
    1.32 +
    1.33 +
    1.34 +/*
    1.35 + * This module is specialized to the case DCTSIZE = 8.
    1.36 + */
    1.37 +
    1.38 +#if DCTSIZE != 8
    1.39 +  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
    1.40 +#endif
    1.41 +
    1.42 +
    1.43 +/* Scaling is the same as in jidctint.c. */
    1.44 +
    1.45 +#if BITS_IN_JSAMPLE == 8
    1.46 +#define CONST_BITS  13
    1.47 +#define PASS1_BITS  2
    1.48 +#else
    1.49 +#define CONST_BITS  13
    1.50 +#define PASS1_BITS  1		/* lose a little precision to avoid overflow */
    1.51 +#endif
    1.52 +
    1.53 +/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
    1.54 + * causing a lot of useless floating-point operations at run time.
    1.55 + * To get around this we use the following pre-calculated constants.
    1.56 + * If you change CONST_BITS you may want to add appropriate values.
    1.57 + * (With a reasonable C compiler, you can just rely on the FIX() macro...)
    1.58 + */
    1.59 +
    1.60 +#if CONST_BITS == 13
    1.61 +#define FIX_0_211164243  ((INT32)  1730)	/* FIX(0.211164243) */
    1.62 +#define FIX_0_509795579  ((INT32)  4176)	/* FIX(0.509795579) */
    1.63 +#define FIX_0_601344887  ((INT32)  4926)	/* FIX(0.601344887) */
    1.64 +#define FIX_0_720959822  ((INT32)  5906)	/* FIX(0.720959822) */
    1.65 +#define FIX_0_765366865  ((INT32)  6270)	/* FIX(0.765366865) */
    1.66 +#define FIX_0_850430095  ((INT32)  6967)	/* FIX(0.850430095) */
    1.67 +#define FIX_0_899976223  ((INT32)  7373)	/* FIX(0.899976223) */
    1.68 +#define FIX_1_061594337  ((INT32)  8697)	/* FIX(1.061594337) */
    1.69 +#define FIX_1_272758580  ((INT32)  10426)	/* FIX(1.272758580) */
    1.70 +#define FIX_1_451774981  ((INT32)  11893)	/* FIX(1.451774981) */
    1.71 +#define FIX_1_847759065  ((INT32)  15137)	/* FIX(1.847759065) */
    1.72 +#define FIX_2_172734803  ((INT32)  17799)	/* FIX(2.172734803) */
    1.73 +#define FIX_2_562915447  ((INT32)  20995)	/* FIX(2.562915447) */
    1.74 +#define FIX_3_624509785  ((INT32)  29692)	/* FIX(3.624509785) */
    1.75 +#else
    1.76 +#define FIX_0_211164243  FIX(0.211164243)
    1.77 +#define FIX_0_509795579  FIX(0.509795579)
    1.78 +#define FIX_0_601344887  FIX(0.601344887)
    1.79 +#define FIX_0_720959822  FIX(0.720959822)
    1.80 +#define FIX_0_765366865  FIX(0.765366865)
    1.81 +#define FIX_0_850430095  FIX(0.850430095)
    1.82 +#define FIX_0_899976223  FIX(0.899976223)
    1.83 +#define FIX_1_061594337  FIX(1.061594337)
    1.84 +#define FIX_1_272758580  FIX(1.272758580)
    1.85 +#define FIX_1_451774981  FIX(1.451774981)
    1.86 +#define FIX_1_847759065  FIX(1.847759065)
    1.87 +#define FIX_2_172734803  FIX(2.172734803)
    1.88 +#define FIX_2_562915447  FIX(2.562915447)
    1.89 +#define FIX_3_624509785  FIX(3.624509785)
    1.90 +#endif
    1.91 +
    1.92 +
    1.93 +/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
    1.94 + * For 8-bit samples with the recommended scaling, all the variable
    1.95 + * and constant values involved are no more than 16 bits wide, so a
    1.96 + * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
    1.97 + * For 12-bit samples, a full 32-bit multiplication will be needed.
    1.98 + */
    1.99 +
   1.100 +#if BITS_IN_JSAMPLE == 8
   1.101 +#define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
   1.102 +#else
   1.103 +#define MULTIPLY(var,const)  ((var) * (const))
   1.104 +#endif
   1.105 +
   1.106 +
   1.107 +/* Dequantize a coefficient by multiplying it by the multiplier-table
   1.108 + * entry; produce an int result.  In this module, both inputs and result
   1.109 + * are 16 bits or less, so either int or short multiply will work.
   1.110 + */
   1.111 +
   1.112 +#define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))
   1.113 +
   1.114 +
   1.115 +/*
   1.116 + * Perform dequantization and inverse DCT on one block of coefficients,
   1.117 + * producing a reduced-size 4x4 output block.
   1.118 + */
   1.119 +
   1.120 +GLOBAL(void)
   1.121 +jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
   1.122 +	       JCOEFPTR coef_block,
   1.123 +	       JSAMPARRAY output_buf, JDIMENSION output_col)
   1.124 +{
   1.125 +  INT32 tmp0, tmp2, tmp10, tmp12;
   1.126 +  INT32 z1, z2, z3, z4;
   1.127 +  JCOEFPTR inptr;
   1.128 +  ISLOW_MULT_TYPE * quantptr;
   1.129 +  int * wsptr;
   1.130 +  JSAMPROW outptr;
   1.131 +  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   1.132 +  int ctr;
   1.133 +  int workspace[DCTSIZE*4];	/* buffers data between passes */
   1.134 +  SHIFT_TEMPS
   1.135 +
   1.136 +  /* Pass 1: process columns from input, store into work array. */
   1.137 +
   1.138 +  inptr = coef_block;
   1.139 +  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   1.140 +  wsptr = workspace;
   1.141 +  for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
   1.142 +    /* Don't bother to process column 4, because second pass won't use it */
   1.143 +    if (ctr == DCTSIZE-4)
   1.144 +      continue;
   1.145 +    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
   1.146 +	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
   1.147 +	inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
   1.148 +      /* AC terms all zero; we need not examine term 4 for 4x4 output */
   1.149 +      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
   1.150 +      
   1.151 +      wsptr[DCTSIZE*0] = dcval;
   1.152 +      wsptr[DCTSIZE*1] = dcval;
   1.153 +      wsptr[DCTSIZE*2] = dcval;
   1.154 +      wsptr[DCTSIZE*3] = dcval;
   1.155 +      
   1.156 +      continue;
   1.157 +    }
   1.158 +    
   1.159 +    /* Even part */
   1.160 +    
   1.161 +    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
   1.162 +    tmp0 <<= (CONST_BITS+1);
   1.163 +    
   1.164 +    z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
   1.165 +    z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
   1.166 +
   1.167 +    tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
   1.168 +    
   1.169 +    tmp10 = tmp0 + tmp2;
   1.170 +    tmp12 = tmp0 - tmp2;
   1.171 +    
   1.172 +    /* Odd part */
   1.173 +    
   1.174 +    z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
   1.175 +    z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
   1.176 +    z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
   1.177 +    z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
   1.178 +    
   1.179 +    tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
   1.180 +	 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
   1.181 +	 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
   1.182 +	 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
   1.183 +    
   1.184 +    tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
   1.185 +	 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
   1.186 +	 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
   1.187 +	 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
   1.188 +
   1.189 +    /* Final output stage */
   1.190 +    
   1.191 +    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
   1.192 +    wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
   1.193 +    wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
   1.194 +    wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
   1.195 +  }
   1.196 +  
   1.197 +  /* Pass 2: process 4 rows from work array, store into output array. */
   1.198 +
   1.199 +  wsptr = workspace;
   1.200 +  for (ctr = 0; ctr < 4; ctr++) {
   1.201 +    outptr = output_buf[ctr] + output_col;
   1.202 +    /* It's not clear whether a zero row test is worthwhile here ... */
   1.203 +
   1.204 +#ifndef NO_ZERO_ROW_TEST
   1.205 +    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
   1.206 +	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
   1.207 +      /* AC terms all zero */
   1.208 +      JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
   1.209 +				  & RANGE_MASK];
   1.210 +      
   1.211 +      outptr[0] = dcval;
   1.212 +      outptr[1] = dcval;
   1.213 +      outptr[2] = dcval;
   1.214 +      outptr[3] = dcval;
   1.215 +      
   1.216 +      wsptr += DCTSIZE;		/* advance pointer to next row */
   1.217 +      continue;
   1.218 +    }
   1.219 +#endif
   1.220 +    
   1.221 +    /* Even part */
   1.222 +    
   1.223 +    tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1);
   1.224 +    
   1.225 +    tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065)
   1.226 +	 + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865);
   1.227 +    
   1.228 +    tmp10 = tmp0 + tmp2;
   1.229 +    tmp12 = tmp0 - tmp2;
   1.230 +    
   1.231 +    /* Odd part */
   1.232 +    
   1.233 +    z1 = (INT32) wsptr[7];
   1.234 +    z2 = (INT32) wsptr[5];
   1.235 +    z3 = (INT32) wsptr[3];
   1.236 +    z4 = (INT32) wsptr[1];
   1.237 +    
   1.238 +    tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
   1.239 +	 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
   1.240 +	 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
   1.241 +	 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
   1.242 +    
   1.243 +    tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
   1.244 +	 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
   1.245 +	 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
   1.246 +	 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
   1.247 +
   1.248 +    /* Final output stage */
   1.249 +    
   1.250 +    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
   1.251 +					  CONST_BITS+PASS1_BITS+3+1)
   1.252 +			    & RANGE_MASK];
   1.253 +    outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
   1.254 +					  CONST_BITS+PASS1_BITS+3+1)
   1.255 +			    & RANGE_MASK];
   1.256 +    outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
   1.257 +					  CONST_BITS+PASS1_BITS+3+1)
   1.258 +			    & RANGE_MASK];
   1.259 +    outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
   1.260 +					  CONST_BITS+PASS1_BITS+3+1)
   1.261 +			    & RANGE_MASK];
   1.262 +    
   1.263 +    wsptr += DCTSIZE;		/* advance pointer to next row */
   1.264 +  }
   1.265 +}
   1.266 +
   1.267 +
   1.268 +/*
   1.269 + * Perform dequantization and inverse DCT on one block of coefficients,
   1.270 + * producing a reduced-size 2x2 output block.
   1.271 + */
   1.272 +
   1.273 +GLOBAL(void)
   1.274 +jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
   1.275 +	       JCOEFPTR coef_block,
   1.276 +	       JSAMPARRAY output_buf, JDIMENSION output_col)
   1.277 +{
   1.278 +  INT32 tmp0, tmp10, z1;
   1.279 +  JCOEFPTR inptr;
   1.280 +  ISLOW_MULT_TYPE * quantptr;
   1.281 +  int * wsptr;
   1.282 +  JSAMPROW outptr;
   1.283 +  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   1.284 +  int ctr;
   1.285 +  int workspace[DCTSIZE*2];	/* buffers data between passes */
   1.286 +  SHIFT_TEMPS
   1.287 +
   1.288 +  /* Pass 1: process columns from input, store into work array. */
   1.289 +
   1.290 +  inptr = coef_block;
   1.291 +  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   1.292 +  wsptr = workspace;
   1.293 +  for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
   1.294 +    /* Don't bother to process columns 2,4,6 */
   1.295 +    if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
   1.296 +      continue;
   1.297 +    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
   1.298 +	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
   1.299 +      /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
   1.300 +      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
   1.301 +      
   1.302 +      wsptr[DCTSIZE*0] = dcval;
   1.303 +      wsptr[DCTSIZE*1] = dcval;
   1.304 +      
   1.305 +      continue;
   1.306 +    }
   1.307 +    
   1.308 +    /* Even part */
   1.309 +    
   1.310 +    z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
   1.311 +    tmp10 = z1 << (CONST_BITS+2);
   1.312 +    
   1.313 +    /* Odd part */
   1.314 +
   1.315 +    z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
   1.316 +    tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
   1.317 +    z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
   1.318 +    tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
   1.319 +    z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
   1.320 +    tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
   1.321 +    z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
   1.322 +    tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
   1.323 +
   1.324 +    /* Final output stage */
   1.325 +    
   1.326 +    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
   1.327 +    wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
   1.328 +  }
   1.329 +  
   1.330 +  /* Pass 2: process 2 rows from work array, store into output array. */
   1.331 +
   1.332 +  wsptr = workspace;
   1.333 +  for (ctr = 0; ctr < 2; ctr++) {
   1.334 +    outptr = output_buf[ctr] + output_col;
   1.335 +    /* It's not clear whether a zero row test is worthwhile here ... */
   1.336 +
   1.337 +#ifndef NO_ZERO_ROW_TEST
   1.338 +    if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
   1.339 +      /* AC terms all zero */
   1.340 +      JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
   1.341 +				  & RANGE_MASK];
   1.342 +      
   1.343 +      outptr[0] = dcval;
   1.344 +      outptr[1] = dcval;
   1.345 +      
   1.346 +      wsptr += DCTSIZE;		/* advance pointer to next row */
   1.347 +      continue;
   1.348 +    }
   1.349 +#endif
   1.350 +    
   1.351 +    /* Even part */
   1.352 +    
   1.353 +    tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2);
   1.354 +    
   1.355 +    /* Odd part */
   1.356 +
   1.357 +    tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
   1.358 +	 + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
   1.359 +	 + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
   1.360 +	 + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
   1.361 +
   1.362 +    /* Final output stage */
   1.363 +    
   1.364 +    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
   1.365 +					  CONST_BITS+PASS1_BITS+3+2)
   1.366 +			    & RANGE_MASK];
   1.367 +    outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
   1.368 +					  CONST_BITS+PASS1_BITS+3+2)
   1.369 +			    & RANGE_MASK];
   1.370 +    
   1.371 +    wsptr += DCTSIZE;		/* advance pointer to next row */
   1.372 +  }
   1.373 +}
   1.374 +
   1.375 +
   1.376 +/*
   1.377 + * Perform dequantization and inverse DCT on one block of coefficients,
   1.378 + * producing a reduced-size 1x1 output block.
   1.379 + */
   1.380 +
   1.381 +GLOBAL(void)
   1.382 +jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
   1.383 +	       JCOEFPTR coef_block,
   1.384 +	       JSAMPARRAY output_buf, JDIMENSION output_col)
   1.385 +{
   1.386 +  int dcval;
   1.387 +  ISLOW_MULT_TYPE * quantptr;
   1.388 +  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   1.389 +  SHIFT_TEMPS
   1.390 +
   1.391 +  /* We hardly need an inverse DCT routine for this: just take the
   1.392 +   * average pixel value, which is one-eighth of the DC coefficient.
   1.393 +   */
   1.394 +  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   1.395 +  dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
   1.396 +  dcval = (int) DESCALE((INT32) dcval, 3);
   1.397 +
   1.398 +  output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
   1.399 +}
   1.400 +
   1.401 +#endif /* IDCT_SCALING_SUPPORTED */