From 7f3f5f46c224c95673e85cdc06d5ac9d6a08701f Mon Sep 17 00:00:00 2001 From: Vitor Sessak Date: Wed, 20 Jan 2010 00:39:47 +0000 Subject: Floating point discrete cosine transform Originally committed as revision 21338 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/Makefile | 1 + libavcodec/dct.c | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++ libavcodec/dsputil.h | 20 ++++++++ libavcodec/fft-test.c | 66 +++++++++++++++++++++++- 4 files changed, 225 insertions(+), 1 deletion(-) create mode 100644 libavcodec/dct.c (limited to 'libavcodec') diff --git a/libavcodec/Makefile b/libavcodec/Makefile index 96a703b57f..3888589511 100644 --- a/libavcodec/Makefile +++ b/libavcodec/Makefile @@ -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 diff --git a/libavcodec/dct.c b/libavcodec/dct.c new file mode 100644 index 0000000000..3776349df9 --- /dev/null +++ b/libavcodec/dct.c @@ -0,0 +1,139 @@ +/* + * (I)DCT Transforms + * Copyright (c) 2009 Peter Ross + * Copyright (c) 2010 Alex Converse + * 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 +#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); +} diff --git a/libavcodec/dsputil.h b/libavcodec/dsputil.h index 1476ae7ba3..65088c11ca 100644 --- a/libavcodec/dsputil.h +++ b/libavcodec/dsputil.h @@ -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)\ diff --git a/libavcodec/fft-test.c b/libavcodec/fft-test.c index ed1b370a40..f07ef032f8 100644 --- a/libavcodec/fft-test.c +++ b/libavcodec/fft-test.c @@ -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<