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Floating point discrete cosine transform

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Originally committed as revision 21338 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Vitor Sessak 2010-01-20 00:39:47 +00:00
parent c4f2b6dce3
commit 7f3f5f46c2
5 changed files with 227 additions and 1 deletions
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2
configure vendored
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@ -99,6 +99,7 @@ Configuration options:
--disable-fastdiv disable table-based division
--enable-small optimize for size instead of speed
--disable-aandct disable AAN DCT code
--disable-dct disable DCT code
--disable-fft disable FFT code
--disable-golomb disable Golomb code
--disable-lpc disable LPC code
@ -862,6 +863,7 @@ CONFIG_LIST="
avisynth
beos_netserver
bzlib
dct
doc
fastdiv
ffmpeg

1
libavcodec/Makefile
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@ -27,6 +27,7 @@ OBJS = allcodecs.o \
# parts needed for many different codecs
OBJS-$(CONFIG_AANDCT) += aandcttab.o
OBJS-$(CONFIG_ENCODERS) += faandct.o jfdctfst.o jfdctint.o
OBJS-$(CONFIG_DCT) += dct.o
FFT-OBJS-$(CONFIG_HARDCODED_TABLES) += cos_tables.o
OBJS-$(CONFIG_FFT) += fft.o $(FFT-OBJS-yes)
OBJS-$(CONFIG_GOLOMB) += golomb.o

139
libavcodec/dct.c Normal file
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@ -0,0 +1,139 @@
/*
* (I)DCT Transforms
* Copyright (c) 2009 Peter Ross <pross@xvid.org>
* Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
* Copyright (c) 2010 Vitor Sessak
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file libavcodec/dct.c
* (Inverse) Discrete Cosine Transforms. These are also known as the
* type II and type III DCTs respectively.
*/
#include <math.h>
#include "dsputil.h"
av_cold int ff_dct_init(DCTContext *s, int nbits, int inverse)
{
int n = 1 << nbits;
int i;
s->nbits = nbits;
s->inverse = inverse;
ff_init_ff_cos_tabs(nbits+2);
s->costab = ff_cos_tabs[nbits+2];
s->csc2 = av_malloc(n/2 * sizeof(FFTSample));
if (ff_rdft_init(&s->rdft, nbits, inverse) < 0) {
av_free(s->csc2);
return -1;
}
for (i = 0; i < n/2; i++)
s->csc2[i] = 0.5 / sin((M_PI / (2*n) * (2*i + 1)));
return 0;
}
/* sin((M_PI * x / (2*n)) */
#define SIN(s,n,x) (s->costab[(n) - (x)])
/* cos((M_PI * x / (2*n)) */
#define COS(s,n,x) (s->costab[x])
static void ff_dct_calc_c(DCTContext *ctx, FFTSample *data)
{
int n = 1 << ctx->nbits;
int i;
if (ctx->inverse) {
float next = data[n - 1];
float inv_n = 1.0f / n;
for (i = n - 2; i >= 2; i -= 2) {
float val1 = data[i ];
float val2 = data[i - 1] - data[i + 1];
float c = COS(ctx, n, i);
float s = SIN(ctx, n, i);
data[i ] = c * val1 + s * val2;
data[i + 1] = s * val1 - c * val2;
}
data[1] = 2 * next;
ff_rdft_calc(&ctx->rdft, data);
for (i = 0; i < n / 2; i++) {
float tmp1 = data[i ] * inv_n;
float tmp2 = data[n - i - 1] * inv_n;
float csc = ctx->csc2[i] * (tmp1 - tmp2);
tmp1 += tmp2;
data[i ] = tmp1 + csc;
data[n - i - 1] = tmp1 - csc;
}
} else {
float next;
for (i=0; i < n/2; i++) {
float tmp1 = data[i ];
float tmp2 = data[n - i - 1];
float s = SIN(ctx, n, 2*i + 1);
s *= tmp1 - tmp2;
tmp1 = (tmp1 + tmp2) * 0.5f;
data[i ] = tmp1 + s;
data[n-i-1] = tmp1 - s;
}
ff_rdft_calc(&ctx->rdft, data);
next = data[1] * 0.5;
data[1] *= -1;
for (i = n - 2; i >= 0; i -= 2) {
float inr = data[i ];
float ini = data[i + 1];
float c = COS(ctx, n, i);
float s = SIN(ctx, n, i);
data[i ] = c * inr + s * ini;
data[i+1] = next;
next += s * inr - c * ini;
}
}
}
void ff_dct_calc(DCTContext *s, FFTSample *data)
{
ff_dct_calc_c(s, data);
}
av_cold void ff_dct_end(DCTContext *s)
{
ff_rdft_end(&s->rdft);
av_free(s->csc2);
}

20
libavcodec/dsputil.h
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@ -899,6 +899,26 @@ int ff_rdft_init(RDFTContext *s, int nbits, enum RDFTransformType trans);
void ff_rdft_calc(RDFTContext *s, FFTSample *data);
void ff_rdft_end(RDFTContext *s);
/* Discrete Cosine Transform */
typedef struct {
int nbits;
int inverse;
FFTSample *data;
RDFTContext rdft;
const float *costab;
FFTSample *csc2;
} DCTContext;
/**
* Sets up (Inverse)DCT.
* @param nbits log2 of the length of the input array
* @param inverse >0 forward transform, <0 inverse transform
*/
int ff_dct_init(DCTContext *s, int nbits, int inverse);
void ff_dct_calc(DCTContext *s, FFTSample *data);
void ff_dct_end (DCTContext *s);
#define WRAPPER8_16(name8, name16)\
static int name16(void /*MpegEncContext*/ *s, uint8_t *dst, uint8_t *src, int stride, int h){\
return name8(s, dst , src , stride, h)\

66
libavcodec/fft-test.c
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@ -128,6 +128,39 @@ static void mdct_ref(float *output, float *input, int nbits)
}
}
static void idct_ref(float *output, float *input, int nbits)
{
int n = 1<<nbits;
int k, i;
double a, s;
/* do it by hand */
for (i = 0; i < n; i++) {
s = 0.5 * input[0];
for (k = 1; k < n; k++) {
a = M_PI*k*(i+0.5) / n;
s += input[k] * cos(a);
}
output[i] = 2 * s / n;
}
}
static void dct_ref(float *output, float *input, int nbits)
{
int n = 1<<nbits;
int k, i;
double a, s;
/* do it by hand */
for (k = 0; k < n; k++) {
s = 0;
for (i = 0; i < n; i++) {
a = M_PI*k*(i+0.5) / n;
s += input[i] * cos(a);
}
output[k] = s;
}
}
static float frandom(AVLFG *prng)
{
@ -166,6 +199,7 @@ static void help(void)
"-h print this help\n"
"-s speed test\n"
"-m (I)MDCT test\n"
"-d (I)DCT test\n"
"-i inverse transform test\n"
"-n b set the transform size to 2^b\n"
"-f x set scale factor for output data of (I)MDCT to x\n"
@ -177,6 +211,7 @@ enum tf_transform {
TRANSFORM_FFT,
TRANSFORM_MDCT,
TRANSFORM_RDFT,
TRANSFORM_DCT,
};
int main(int argc, char **argv)
@ -190,6 +225,7 @@ int main(int argc, char **argv)
FFTContext s1, *s = &s1;
FFTContext m1, *m = &m1;
RDFTContext r1, *r = &r1;
DCTContext d1, *d = &d1;
int fft_nbits, fft_size, fft_size_2;
double scale = 1.0;
AVLFG prng;
@ -197,7 +233,7 @@ int main(int argc, char **argv)
fft_nbits = 9;
for(;;) {
c = getopt(argc, argv, "hsimrn:f:");
c = getopt(argc, argv, "hsimrdn:f:");
if (c == -1)
break;
switch(c) {
@ -216,6 +252,9 @@ int main(int argc, char **argv)
case 'r':
transform = TRANSFORM_RDFT;
break;
case 'd':
transform = TRANSFORM_DCT;
break;
case 'n':
fft_nbits = atoi(optarg);
break;
@ -257,6 +296,13 @@ int main(int argc, char **argv)
ff_rdft_init(r, fft_nbits, do_inverse ? IRDFT : RDFT);
fft_ref_init(fft_nbits, do_inverse);
break;
case TRANSFORM_DCT:
if (do_inverse)
av_log(NULL, AV_LOG_INFO,"IDCT");
else
av_log(NULL, AV_LOG_INFO,"DCT");
ff_dct_init(d, fft_nbits, do_inverse);
break;
}
av_log(NULL, AV_LOG_INFO," %d test\n", fft_size);
@ -321,6 +367,17 @@ int main(int argc, char **argv)
tab_ref[0].im = tab_ref[fft_size_2].re;
check_diff((float *)tab_ref, (float *)tab2, fft_size, 1.0);
}
break;
case TRANSFORM_DCT:
memcpy(tab, tab1, fft_size * sizeof(FFTComplex));
ff_dct_calc(d, tab);
if (do_inverse) {
idct_ref(tab_ref, tab1, fft_nbits);
} else {
dct_ref(tab_ref, tab1, fft_nbits);
}
check_diff((float *)tab_ref, (float *)tab, fft_size, 1.0);
break;
}
/* do a speed test */
@ -351,6 +408,10 @@ int main(int argc, char **argv)
memcpy(tab2, tab1, fft_size * sizeof(FFTSample));
ff_rdft_calc(r, tab2);
break;
case TRANSFORM_DCT:
memcpy(tab2, tab1, fft_size * sizeof(FFTSample));
ff_dct_calc(d, tab2);
break;
}
}
duration = gettime() - time_start;
@ -374,6 +435,9 @@ int main(int argc, char **argv)
case TRANSFORM_RDFT:
ff_rdft_end(r);
break;
case TRANSFORM_DCT:
ff_dct_end(d);
break;
}
return 0;
}