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Split up the forward DCT routine into three stages

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Divide it into sample conversion, DCT and quantization in order to
easily provide alternative implementations of each stage.
This commit is contained in:
Pierre Ossman
2009-03-09 10:37:20 +00:00
parent d7bacc0721
commit a4f55b50c9
2 changed files with 201 additions and 113 deletions
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311
jcdctmgr.c
View File

@@ -19,11 +19,30 @@
/* Private subobject for this module */
typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));
typedef JMETHOD(void, convsamp_method_ptr,
(JSAMPARRAY sample_data, JDIMENSION start_col,
DCTELEM * workspace));
typedef JMETHOD(void, float_convsamp_method_ptr,
(JSAMPARRAY sample_data, JDIMENSION start_col,
FAST_FLOAT *workspace));
typedef JMETHOD(void, quantize_method_ptr,
(JCOEFPTR coef_block, DCTELEM * divisors,
DCTELEM * workspace));
typedef JMETHOD(void, float_quantize_method_ptr,
(JCOEFPTR coef_block, FAST_FLOAT * divisors,
FAST_FLOAT * workspace));
typedef struct {
struct jpeg_forward_dct pub; /* public fields */
/* Pointer to the DCT routine actually in use */
forward_DCT_method_ptr do_dct;
forward_DCT_method_ptr dct;
convsamp_method_ptr convsamp;
quantize_method_ptr quantize;
/* The actual post-DCT divisors --- not identical to the quant table
* entries, because of scaling (especially for an unnormalized DCT).
@@ -33,7 +52,9 @@ typedef struct {
#ifdef DCT_FLOAT_SUPPORTED
/* Same as above for the floating-point case. */
float_DCT_method_ptr do_float_dct;
float_DCT_method_ptr float_dct;
float_convsamp_method_ptr float_convsamp;
float_quantize_method_ptr float_quantize;
FAST_FLOAT * float_divisors[NUM_QUANT_TBLS];
#endif
} my_fdct_controller;
@@ -168,6 +189,88 @@ start_pass_fdctmgr (j_compress_ptr cinfo)
}
/*
* Load data into workspace, applying unsigned->signed conversion.
*/
METHODDEF(void)
convsamp (JSAMPARRAY sample_data, JDIMENSION start_col, DCTELEM * workspace)
{
register DCTELEM *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
#else
{
register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--)
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
}
#endif
}
}
/*
* Quantize/descale the coefficients, and store into coef_blocks[].
*/
METHODDEF(void)
quantize (JCOEFPTR coef_block, DCTELEM * divisors, DCTELEM * workspace)
{
register DCTELEM temp, qval;
register int i;
register JCOEFPTR output_ptr = coef_block;
for (i = 0; i < DCTSIZE2; i++) {
qval = divisors[i];
temp = workspace[i];
/* Divide the coefficient value by qval, ensuring proper rounding.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
*
* In most files, at least half of the output values will be zero
* (at default quantization settings, more like three-quarters...)
* so we should ensure that this case is fast. On many machines,
* a comparison is enough cheaper than a divide to make a special test
* a win. Since both inputs will be nonnegative, we need only test
* for a < b to discover whether a/b is 0.
* If your machine's division is fast enough, define FAST_DIVIDE.
*/
#ifdef FAST_DIVIDE
#define DIVIDE_BY(a,b) a /= b
#else
#define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0
#endif
if (temp < 0) {
temp = -temp;
temp += qval>>1; /* for rounding */
DIVIDE_BY(temp, qval);
temp = -temp;
} else {
temp += qval>>1; /* for rounding */
DIVIDE_BY(temp, qval);
}
output_ptr[i] = (JCOEF) temp;
}
}
/*
* Perform forward DCT on one or more blocks of a component.
*
@@ -185,87 +288,86 @@ forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr,
{
/* This routine is heavily used, so it's worth coding it tightly. */
my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
forward_DCT_method_ptr do_dct = fdct->do_dct;
DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
DCTELEM workspace[DCTSIZE2]; /* work area for FDCT subroutine */
JDIMENSION bi;
/* Make sure the compiler doesn't look up these every pass */
forward_DCT_method_ptr do_dct = fdct->dct;
convsamp_method_ptr do_convsamp = fdct->convsamp;
quantize_method_ptr do_quantize = fdct->quantize;
sample_data += start_row; /* fold in the vertical offset once */
for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
/* Load data into workspace, applying unsigned->signed conversion */
{ register DCTELEM *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
#else
{ register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--) {
*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
}
}
#endif
}
}
(*do_convsamp) (sample_data, start_col, workspace);
/* Perform the DCT */
(*do_dct) (workspace);
/* Quantize/descale the coefficients, and store into coef_blocks[] */
{ register DCTELEM temp, qval;
register int i;
register JCOEFPTR output_ptr = coef_blocks[bi];
for (i = 0; i < DCTSIZE2; i++) {
qval = divisors[i];
temp = workspace[i];
/* Divide the coefficient value by qval, ensuring proper rounding.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
*
* In most files, at least half of the output values will be zero
* (at default quantization settings, more like three-quarters...)
* so we should ensure that this case is fast. On many machines,
* a comparison is enough cheaper than a divide to make a special test
* a win. Since both inputs will be nonnegative, we need only test
* for a < b to discover whether a/b is 0.
* If your machine's division is fast enough, define FAST_DIVIDE.
*/
#ifdef FAST_DIVIDE
#define DIVIDE_BY(a,b) a /= b
#else
#define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0
#endif
if (temp < 0) {
temp = -temp;
temp += qval>>1; /* for rounding */
DIVIDE_BY(temp, qval);
temp = -temp;
} else {
temp += qval>>1; /* for rounding */
DIVIDE_BY(temp, qval);
}
output_ptr[i] = (JCOEF) temp;
}
}
(*do_quantize) (coef_blocks[bi], divisors, workspace);
}
}
#ifdef DCT_FLOAT_SUPPORTED
METHODDEF(void)
convsamp_float (JSAMPARRAY sample_data, JDIMENSION start_col, FAST_FLOAT * workspace)
{
register FAST_FLOAT *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
#else
{
register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--)
*workspaceptr++ = (FAST_FLOAT)
(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
}
#endif
}
}
METHODDEF(void)
quantize_float (JCOEFPTR coef_block, FAST_FLOAT * divisors, FAST_FLOAT * workspace)
{
register FAST_FLOAT temp;
register int i;
register JCOEFPTR output_ptr = coef_block;
for (i = 0; i < DCTSIZE2; i++) {
/* Apply the quantization and scaling factor */
temp = workspace[i] * divisors[i];
/* Round to nearest integer.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
* The maximum coefficient size is +-16K (for 12-bit data), so this
* code should work for either 16-bit or 32-bit ints.
*/
output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384);
}
}
METHODDEF(void)
forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr,
JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
@@ -275,62 +377,26 @@ forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr,
{
/* This routine is heavily used, so it's worth coding it tightly. */
my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
float_DCT_method_ptr do_dct = fdct->do_float_dct;
FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */
JDIMENSION bi;
/* Make sure the compiler doesn't look up these every pass */
float_DCT_method_ptr do_dct = fdct->float_dct;
float_convsamp_method_ptr do_convsamp = fdct->float_convsamp;
float_quantize_method_ptr do_quantize = fdct->float_quantize;
sample_data += start_row; /* fold in the vertical offset once */
for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
/* Load data into workspace, applying unsigned->signed conversion */
{ register FAST_FLOAT *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
#else
{ register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--) {
*workspaceptr++ = (FAST_FLOAT)
(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
}
}
#endif
}
}
(*do_convsamp) (sample_data, start_col, workspace);
/* Perform the DCT */
(*do_dct) (workspace);
/* Quantize/descale the coefficients, and store into coef_blocks[] */
{ register FAST_FLOAT temp;
register int i;
register JCOEFPTR output_ptr = coef_blocks[bi];
for (i = 0; i < DCTSIZE2; i++) {
/* Apply the quantization and scaling factor */
temp = workspace[i] * divisors[i];
/* Round to nearest integer.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
* The maximum coefficient size is +-16K (for 12-bit data), so this
* code should work for either 16-bit or 32-bit ints.
*/
output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384);
}
}
(*do_quantize) (coef_blocks[bi], divisors, workspace);
}
}
@@ -353,23 +419,48 @@ jinit_forward_dct (j_compress_ptr cinfo)
cinfo->fdct = (struct jpeg_forward_dct *) fdct;
fdct->pub.start_pass = start_pass_fdctmgr;
/* First determine the DCT... */
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
fdct->pub.forward_DCT = forward_DCT;
fdct->do_dct = jpeg_fdct_islow;
fdct->dct = jpeg_fdct_islow;
break;
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
fdct->pub.forward_DCT = forward_DCT;
fdct->do_dct = jpeg_fdct_ifast;
fdct->dct = jpeg_fdct_ifast;
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
fdct->pub.forward_DCT = forward_DCT_float;
fdct->do_float_dct = jpeg_fdct_float;
fdct->float_dct = jpeg_fdct_float;
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
/* ...then the supporting stages. */
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
#endif
#if defined(DCT_ISLOW_SUPPORTED) || defined(DCT_IFAST_SUPPORTED)
fdct->convsamp = convsamp;
fdct->quantize = quantize;
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
fdct->float_convsamp = convsamp_float;
fdct->float_quantize = quantize_float;
break;
#endif
default:

3
jdct.h
View File

@@ -32,9 +32,6 @@ typedef int DCTELEM; /* 16 or 32 bits is fine */
typedef INT32 DCTELEM; /* must have 32 bits */
#endif
typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));
/*
* An inverse DCT routine is given a pointer to the input JBLOCK and a pointer