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Diffstat (limited to 'v4l2-apps/libv4l/libv4lconvert/jidctflt.c')
| -rw-r--r-- | v4l2-apps/libv4l/libv4lconvert/jidctflt.c | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/v4l2-apps/libv4l/libv4lconvert/jidctflt.c b/v4l2-apps/libv4l/libv4lconvert/jidctflt.c new file mode 100644 index 000000000..532abc7ea --- /dev/null +++ b/v4l2-apps/libv4l/libv4lconvert/jidctflt.c @@ -0,0 +1,286 @@ +/* + * jidctflt.c + * + * Copyright (C) 1994-1998, Thomas G. Lane. + * This file is part of the Independent JPEG Group's software. + * + * The authors make NO WARRANTY or representation, either express or implied, + * with respect to this software, its quality, accuracy, merchantability, or + * fitness for a particular purpose. This software is provided "AS IS", and you, + * its user, assume the entire risk as to its quality and accuracy. + * + * This software is copyright (C) 1991-1998, Thomas G. Lane. + * All Rights Reserved except as specified below. + * + * Permission is hereby granted to use, copy, modify, and distribute this + * software (or portions thereof) for any purpose, without fee, subject to these + * conditions: + * (1) If any part of the source code for this software is distributed, then this + * README file must be included, with this copyright and no-warranty notice + * unaltered; and any additions, deletions, or changes to the original files + * must be clearly indicated in accompanying documentation. + * (2) If only executable code is distributed, then the accompanying + * documentation must state that "this software is based in part on the work of + * the Independent JPEG Group". + * (3) Permission for use of this software is granted only if the user accepts + * full responsibility for any undesirable consequences; the authors accept + * NO LIABILITY for damages of any kind. + * + * These conditions apply to any software derived from or based on the IJG code, + * not just to the unmodified library. If you use our work, you ought to + * acknowledge us. + * + * Permission is NOT granted for the use of any IJG author's name or company name + * in advertising or publicity relating to this software or products derived from + * it. This software may be referred to only as "the Independent JPEG Group's + * software". + * + * We specifically permit and encourage the use of this software as the basis of + * commercial products, provided that all warranty or liability claims are + * assumed by the product vendor. + * + * + * This file contains a floating-point implementation of the + * inverse DCT (Discrete Cosine Transform). In the IJG code, this routine + * must also perform dequantization of the input coefficients. + * + * This implementation should be more accurate than either of the integer + * IDCT implementations. However, it may not give the same results on all + * machines because of differences in roundoff behavior. Speed will depend + * on the hardware's floating point capacity. + * + * 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 Arai, Agui, and Nakajima's algorithm for + * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in + * Japanese, but the algorithm is described in the Pennebaker & Mitchell + * JPEG textbook (see REFERENCES section in file README). The following code + * is based directly on figure 4-8 in P&M. + * While an 8-point DCT cannot be done in less than 11 multiplies, it is + * possible to arrange the computation so that many of the multiplies are + * simple scalings of the final outputs. These multiplies can then be + * folded into the multiplications or divisions by the JPEG quantization + * table entries. The AA&N method leaves only 5 multiplies and 29 adds + * to be done in the DCT itself. + * The primary disadvantage of this method is that with a fixed-point + * implementation, accuracy is lost due to imprecise representation of the + * scaled quantization values. However, that problem does not arise if + * we use floating point arithmetic. + */ + +#include <stdint.h> +#include "tinyjpeg-internal.h" + +#define FAST_FLOAT float +#define DCTSIZE 8 +#define DCTSIZE2 (DCTSIZE*DCTSIZE) + +#define DEQUANTIZE(coef,quantval) (((FAST_FLOAT) (coef)) * (quantval)) + +#if defined(__GNUC__) && (defined(__i686__) || defined(__x86_64__)) + +static inline unsigned char descale_and_clamp(int x, int shift) +{ + __asm__ ( + "add %3,%1\n" + "\tsar %2,%1\n" + "\tsub $-128,%1\n" + "\tcmovl %5,%1\n" /* Use the sub to compare to 0 */ + "\tcmpl %4,%1\n" + "\tcmovg %4,%1\n" + : "=r"(x) + : "0"(x), "Ic"((unsigned char)shift), "ir"(1U<<(shift-1)), "r" (0xff), "r" (0) + ); + return x; +} + +#else +static inline unsigned char descale_and_clamp(int x, int shift) +{ + x += (1UL<<(shift-1)); + if (x<0) + x = (x >> shift) | ((~(0UL)) << (32-(shift))); + else + x >>= shift; + x += 128; + if (x>255) + return 255; + else if (x<0) + return 0; + else + return x; +} +#endif + +/* + * Perform dequantization and inverse DCT on one block of coefficients. + */ + +void +tinyjpeg_idct_float (struct component *compptr, uint8_t *output_buf, int stride) +{ + FAST_FLOAT tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; + FAST_FLOAT tmp10, tmp11, tmp12, tmp13; + FAST_FLOAT z5, z10, z11, z12, z13; + int16_t *inptr; + FAST_FLOAT *quantptr; + FAST_FLOAT *wsptr; + uint8_t *outptr; + int ctr; + FAST_FLOAT workspace[DCTSIZE2]; /* buffers data between passes */ + + /* Pass 1: process columns from input, store into work array. */ + + inptr = compptr->DCT; + quantptr = compptr->Q_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] == 0 && inptr[DCTSIZE*2] == 0 && + inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 && + inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 && + inptr[DCTSIZE*7] == 0) { + /* AC terms all zero */ + FAST_FLOAT dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); + + 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 */ + + tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); + tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); + tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]); + tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); + + tmp10 = tmp0 + tmp2; /* phase 3 */ + tmp11 = tmp0 - tmp2; + + tmp13 = tmp1 + tmp3; /* phases 5-3 */ + tmp12 = (tmp1 - tmp3) * ((FAST_FLOAT) 1.414213562) - tmp13; /* 2*c4 */ + + tmp0 = tmp10 + tmp13; /* phase 2 */ + tmp3 = tmp10 - tmp13; + tmp1 = tmp11 + tmp12; + tmp2 = tmp11 - tmp12; + + /* Odd part */ + + tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); + tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); + tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); + tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); + + z13 = tmp6 + tmp5; /* phase 6 */ + z10 = tmp6 - tmp5; + z11 = tmp4 + tmp7; + z12 = tmp4 - tmp7; + + tmp7 = z11 + z13; /* phase 5 */ + tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); /* 2*c4 */ + + z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */ + tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */ + tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */ + + tmp6 = tmp12 - tmp7; /* phase 2 */ + tmp5 = tmp11 - tmp6; + tmp4 = tmp10 + tmp5; + + wsptr[DCTSIZE*0] = tmp0 + tmp7; + wsptr[DCTSIZE*7] = tmp0 - tmp7; + wsptr[DCTSIZE*1] = tmp1 + tmp6; + wsptr[DCTSIZE*6] = tmp1 - tmp6; + wsptr[DCTSIZE*2] = tmp2 + tmp5; + wsptr[DCTSIZE*5] = tmp2 - tmp5; + wsptr[DCTSIZE*4] = tmp3 + tmp4; + wsptr[DCTSIZE*3] = tmp3 - tmp4; + + 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. */ + + wsptr = workspace; + outptr = output_buf; + for (ctr = 0; ctr < DCTSIZE; ctr++) { + /* 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). + * And testing floats for zero is relatively expensive, so we don't bother. + */ + + /* Even part */ + + tmp10 = wsptr[0] + wsptr[4]; + tmp11 = wsptr[0] - wsptr[4]; + + tmp13 = wsptr[2] + wsptr[6]; + tmp12 = (wsptr[2] - wsptr[6]) * ((FAST_FLOAT) 1.414213562) - tmp13; + + tmp0 = tmp10 + tmp13; + tmp3 = tmp10 - tmp13; + tmp1 = tmp11 + tmp12; + tmp2 = tmp11 - tmp12; + + /* Odd part */ + + z13 = wsptr[5] + wsptr[3]; + z10 = wsptr[5] - wsptr[3]; + z11 = wsptr[1] + wsptr[7]; + z12 = wsptr[1] - wsptr[7]; + + tmp7 = z11 + z13; + tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); + + z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */ + tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */ + tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */ + + tmp6 = tmp12 - tmp7; + tmp5 = tmp11 - tmp6; + tmp4 = tmp10 + tmp5; + + /* Final output stage: scale down by a factor of 8 and range-limit */ + + outptr[0] = descale_and_clamp((int)(tmp0 + tmp7), 3); + outptr[7] = descale_and_clamp((int)(tmp0 - tmp7), 3); + outptr[1] = descale_and_clamp((int)(tmp1 + tmp6), 3); + outptr[6] = descale_and_clamp((int)(tmp1 - tmp6), 3); + outptr[2] = descale_and_clamp((int)(tmp2 + tmp5), 3); + outptr[5] = descale_and_clamp((int)(tmp2 - tmp5), 3); + outptr[4] = descale_and_clamp((int)(tmp3 + tmp4), 3); + outptr[3] = descale_and_clamp((int)(tmp3 - tmp4), 3); + + + wsptr += DCTSIZE; /* advance pointer to next row */ + outptr += stride; + } +} + |