mirror of https://github.com/FFmpeg/FFmpeg.git
Originally committed as revision 26206 to svn://svn.ffmpeg.org/ffmpeg/trunkoldabi
Justin Ruggles
14 years ago
parent
f03424a782
commit
ad6b2c1f6d
4 changed files with 505 additions and 421 deletions
@ -0,0 +1,428 @@ |
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/*
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* The simplest AC-3 encoder |
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* Copyright (c) 2000 Fabrice Bellard |
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* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com> |
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* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de> |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/**
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* @file |
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* fixed-point AC-3 encoder. |
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*/ |
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#include "ac3enc.c" |
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/** Scale a float value by 2^15, convert to an integer, and clip to range -32767..32767. */ |
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#define FIX15(a) av_clip(SCALE_FLOAT(a, 15), -32767, 32767) |
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/**
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* Finalize MDCT and free allocated memory. |
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*/ |
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static av_cold void mdct_end(AC3MDCTContext *mdct) |
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{ |
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mdct->nbits = 0; |
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av_freep(&mdct->costab); |
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av_freep(&mdct->sintab); |
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av_freep(&mdct->xcos1); |
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av_freep(&mdct->xsin1); |
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av_freep(&mdct->rot_tmp); |
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av_freep(&mdct->cplx_tmp); |
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} |
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/**
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* Initialize FFT tables. |
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* @param ln log2(FFT size) |
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*/ |
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static av_cold int fft_init(AVCodecContext *avctx, AC3MDCTContext *mdct, int ln) |
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{ |
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int i, n, n2; |
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float alpha; |
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n = 1 << ln; |
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n2 = n >> 1; |
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FF_ALLOC_OR_GOTO(avctx, mdct->costab, n2 * sizeof(*mdct->costab), fft_alloc_fail); |
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FF_ALLOC_OR_GOTO(avctx, mdct->sintab, n2 * sizeof(*mdct->sintab), fft_alloc_fail); |
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for (i = 0; i < n2; i++) { |
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alpha = 2.0 * M_PI * i / n; |
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mdct->costab[i] = FIX15(cos(alpha)); |
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mdct->sintab[i] = FIX15(sin(alpha)); |
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} |
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return 0; |
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fft_alloc_fail: |
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mdct_end(mdct); |
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return AVERROR(ENOMEM); |
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} |
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/**
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* Initialize MDCT tables. |
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* @param nbits log2(MDCT size) |
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*/ |
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static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct, |
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int nbits) |
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{ |
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int i, n, n4, ret; |
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n = 1 << nbits; |
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n4 = n >> 2; |
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mdct->nbits = nbits; |
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ret = fft_init(avctx, mdct, nbits - 2); |
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if (ret) |
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return ret; |
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mdct->window = ff_ac3_window; |
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FF_ALLOC_OR_GOTO(avctx, mdct->xcos1, n4 * sizeof(*mdct->xcos1), mdct_alloc_fail); |
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FF_ALLOC_OR_GOTO(avctx, mdct->xsin1, n4 * sizeof(*mdct->xsin1), mdct_alloc_fail); |
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FF_ALLOC_OR_GOTO(avctx, mdct->rot_tmp, n * sizeof(*mdct->rot_tmp), mdct_alloc_fail); |
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FF_ALLOC_OR_GOTO(avctx, mdct->cplx_tmp, n4 * sizeof(*mdct->cplx_tmp), mdct_alloc_fail); |
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for (i = 0; i < n4; i++) { |
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float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n; |
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mdct->xcos1[i] = FIX15(-cos(alpha)); |
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mdct->xsin1[i] = FIX15(-sin(alpha)); |
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} |
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return 0; |
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mdct_alloc_fail: |
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mdct_end(mdct); |
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return AVERROR(ENOMEM); |
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} |
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/** Butterfly op */ |
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#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \ |
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{ \
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int ax, ay, bx, by; \
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bx = pre1; \
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by = pim1; \
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ax = qre1; \
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ay = qim1; \
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pre = (bx + ax) >> 1; \
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pim = (by + ay) >> 1; \
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qre = (bx - ax) >> 1; \
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qim = (by - ay) >> 1; \
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} |
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/** Complex multiply */ |
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#define CMUL(pre, pim, are, aim, bre, bim) \ |
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{ \
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pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15; \
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pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15; \
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} |
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/**
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* Calculate a 2^n point complex FFT on 2^ln points. |
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* @param z complex input/output samples |
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* @param ln log2(FFT size) |
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*/ |
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static void fft(AC3MDCTContext *mdct, IComplex *z, int ln) |
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{ |
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int j, l, np, np2; |
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int nblocks, nloops; |
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register IComplex *p,*q; |
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int tmp_re, tmp_im; |
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np = 1 << ln; |
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/* reverse */ |
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for (j = 0; j < np; j++) { |
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int k = av_reverse[j] >> (8 - ln); |
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if (k < j) |
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FFSWAP(IComplex, z[k], z[j]); |
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} |
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/* pass 0 */ |
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p = &z[0]; |
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j = np >> 1; |
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do { |
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BF(p[0].re, p[0].im, p[1].re, p[1].im, |
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p[0].re, p[0].im, p[1].re, p[1].im); |
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p += 2; |
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} while (--j); |
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/* pass 1 */ |
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p = &z[0]; |
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j = np >> 2; |
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do { |
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BF(p[0].re, p[0].im, p[2].re, p[2].im, |
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p[0].re, p[0].im, p[2].re, p[2].im); |
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BF(p[1].re, p[1].im, p[3].re, p[3].im, |
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p[1].re, p[1].im, p[3].im, -p[3].re); |
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p+=4; |
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} while (--j); |
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/* pass 2 .. ln-1 */ |
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nblocks = np >> 3; |
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nloops = 1 << 2; |
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np2 = np >> 1; |
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do { |
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p = z; |
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q = z + nloops; |
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for (j = 0; j < nblocks; j++) { |
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BF(p->re, p->im, q->re, q->im, |
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p->re, p->im, q->re, q->im); |
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p++; |
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q++; |
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for(l = nblocks; l < np2; l += nblocks) { |
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CMUL(tmp_re, tmp_im, mdct->costab[l], -mdct->sintab[l], q->re, q->im); |
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BF(p->re, p->im, q->re, q->im, |
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p->re, p->im, tmp_re, tmp_im); |
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p++; |
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q++; |
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} |
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p += nloops; |
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q += nloops; |
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} |
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nblocks = nblocks >> 1; |
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nloops = nloops << 1; |
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} while (nblocks); |
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} |
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/**
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* Calculate a 512-point MDCT |
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* @param out 256 output frequency coefficients |
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* @param in 512 windowed input audio samples |
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*/ |
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static void mdct512(AC3MDCTContext *mdct, int32_t *out, int16_t *in) |
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{ |
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int i, re, im, n, n2, n4; |
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int16_t *rot = mdct->rot_tmp; |
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IComplex *x = mdct->cplx_tmp; |
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n = 1 << mdct->nbits; |
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n2 = n >> 1; |
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n4 = n >> 2; |
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/* shift to simplify computations */ |
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for (i = 0; i <n4; i++) |
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rot[i] = -in[i + 3*n4]; |
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memcpy(&rot[n4], &in[0], 3*n4*sizeof(*in)); |
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/* pre rotation */ |
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for (i = 0; i < n4; i++) { |
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re = ((int)rot[ 2*i] - (int)rot[ n-1-2*i]) >> 1; |
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im = -((int)rot[n2+2*i] - (int)rot[n2-1-2*i]) >> 1; |
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CMUL(x[i].re, x[i].im, re, im, -mdct->xcos1[i], mdct->xsin1[i]); |
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} |
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fft(mdct, x, mdct->nbits - 2); |
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/* post rotation */ |
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for (i = 0; i < n4; i++) { |
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re = x[i].re; |
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im = x[i].im; |
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CMUL(out[n2-1-2*i], out[2*i], re, im, mdct->xsin1[i], mdct->xcos1[i]); |
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} |
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} |
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/**
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* Apply KBD window to input samples prior to MDCT. |
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*/ |
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static void apply_window(int16_t *output, const int16_t *input, |
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const int16_t *window, int n) |
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{ |
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int i; |
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int n2 = n >> 1; |
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for (i = 0; i < n2; i++) { |
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output[i] = MUL16(input[i], window[i]) >> 15; |
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output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15; |
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} |
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} |
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/**
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* Calculate the log2() of the maximum absolute value in an array. |
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* @param tab input array |
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* @param n number of values in the array |
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* @return log2(max(abs(tab[]))) |
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*/ |
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static int log2_tab(int16_t *tab, int n) |
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{ |
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int i, v; |
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v = 0; |
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for (i = 0; i < n; i++) |
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v |= abs(tab[i]); |
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return av_log2(v); |
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} |
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/**
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* Left-shift each value in an array by a specified amount. |
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* @param tab input array |
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* @param n number of values in the array |
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* @param lshift left shift amount. a negative value means right shift. |
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*/ |
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static void lshift_tab(int16_t *tab, int n, int lshift) |
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{ |
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int i; |
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if (lshift > 0) { |
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for (i = 0; i < n; i++) |
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tab[i] <<= lshift; |
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} else if (lshift < 0) { |
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lshift = -lshift; |
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for (i = 0; i < n; i++) |
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tab[i] >>= lshift; |
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} |
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} |
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/**
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* Normalize the input samples to use the maximum available precision. |
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* This assumes signed 16-bit input samples. Exponents are reduced by 9 to |
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* match the 24-bit internal precision for MDCT coefficients. |
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* |
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* @return exponent shift |
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*/ |
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static int normalize_samples(AC3EncodeContext *s) |
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{ |
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int v = 14 - log2_tab(s->windowed_samples, AC3_WINDOW_SIZE); |
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v = FFMAX(0, v); |
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lshift_tab(s->windowed_samples, AC3_WINDOW_SIZE, v); |
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return v - 9; |
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} |
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#ifdef TEST |
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/*************************************************************************/ |
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/* TEST */ |
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#include "libavutil/lfg.h" |
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#define MDCT_NBITS 9 |
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#define MDCT_SAMPLES (1 << MDCT_NBITS) |
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#define FN (MDCT_SAMPLES/4) |
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static void fft_test(AC3MDCTContext *mdct, AVLFG *lfg) |
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{ |
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IComplex in[FN], in1[FN]; |
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int k, n, i; |
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float sum_re, sum_im, a; |
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for (i = 0; i < FN; i++) { |
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in[i].re = av_lfg_get(lfg) % 65535 - 32767; |
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in[i].im = av_lfg_get(lfg) % 65535 - 32767; |
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in1[i] = in[i]; |
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} |
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fft(mdct, in, 7); |
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/* do it by hand */ |
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for (k = 0; k < FN; k++) { |
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sum_re = 0; |
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sum_im = 0; |
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for (n = 0; n < FN; n++) { |
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a = -2 * M_PI * (n * k) / FN; |
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sum_re += in1[n].re * cos(a) - in1[n].im * sin(a); |
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sum_im += in1[n].re * sin(a) + in1[n].im * cos(a); |
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} |
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av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n", |
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k, in[k].re, in[k].im, sum_re / FN, sum_im / FN); |
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} |
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} |
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static void mdct_test(AC3MDCTContext *mdct, AVLFG *lfg) |
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{ |
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int16_t input[MDCT_SAMPLES]; |
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int32_t output[AC3_MAX_COEFS]; |
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float input1[MDCT_SAMPLES]; |
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float output1[AC3_MAX_COEFS]; |
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float s, a, err, e, emax; |
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int i, k, n; |
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for (i = 0; i < MDCT_SAMPLES; i++) { |
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input[i] = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10; |
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input1[i] = input[i]; |
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} |
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mdct512(mdct, output, input); |
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/* do it by hand */ |
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for (k = 0; k < AC3_MAX_COEFS; k++) { |
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s = 0; |
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for (n = 0; n < MDCT_SAMPLES; n++) { |
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a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES)); |
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s += input1[n] * cos(a); |
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} |
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output1[k] = -2 * s / MDCT_SAMPLES; |
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} |
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err = 0; |
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emax = 0; |
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for (i = 0; i < AC3_MAX_COEFS; i++) { |
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av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]); |
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e = output[i] - output1[i]; |
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if (e > emax) |
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emax = e; |
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err += e * e; |
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} |
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av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax); |
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} |
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int main(void) |
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{ |
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AVLFG lfg; |
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AC3MDCTContext mdct; |
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mdct.avctx = NULL; |
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av_log_set_level(AV_LOG_DEBUG); |
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mdct_init(&mdct, 9); |
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fft_test(&mdct, &lfg); |
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mdct_test(&mdct, &lfg); |
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return 0; |
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} |
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#endif /* TEST */ |
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AVCodec ac3_encoder = { |
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"ac3", |
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AVMEDIA_TYPE_AUDIO, |
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CODEC_ID_AC3, |
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sizeof(AC3EncodeContext), |
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ac3_encode_init, |
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ac3_encode_frame, |
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ac3_encode_close, |
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NULL, |
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.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, |
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.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"), |
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.channel_layouts = ac3_channel_layouts, |
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}; |
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@ -0,0 +1,60 @@ |
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/*
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* The simplest AC-3 encoder |
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* Copyright (c) 2000 Fabrice Bellard |
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* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com> |
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* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de> |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/**
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* @file |
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* fixed-point AC-3 encoder header. |
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*/ |
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#ifndef AVCODEC_AC3ENC_FIXED_H |
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#define AVCODEC_AC3ENC_FIXED_H |
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#include <stdint.h> |
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typedef int16_t SampleType; |
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typedef int32_t CoefType; |
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#define SCALE_COEF(a) (a) |
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/**
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* Compex number. |
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* Used in fixed-point MDCT calculation. |
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*/ |
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typedef struct IComplex { |
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int16_t re,im; |
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} IComplex; |
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typedef struct AC3MDCTContext { |
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const int16_t *window; ///< MDCT window function
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int nbits; ///< log2(transform size)
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int16_t *costab; ///< FFT cos table
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int16_t *sintab; ///< FFT sin table
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int16_t *xcos1; ///< MDCT cos table
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int16_t *xsin1; ///< MDCT sin table
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int16_t *rot_tmp; ///< temp buffer for pre-rotated samples
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IComplex *cplx_tmp; ///< temp buffer for complex pre-rotated samples
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} AC3MDCTContext; |
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#endif /* AVCODEC_AC3ENC_FIXED_H */ |
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