441 lines
11 KiB
C
441 lines
11 KiB
C
/*
|
|
* The simplest AC-3 encoder
|
|
* Copyright (c) 2000 Fabrice Bellard
|
|
* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
|
|
* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
|
|
*
|
|
* 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 Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* fixed-point AC-3 encoder.
|
|
*/
|
|
|
|
#undef CONFIG_AC3ENC_FLOAT
|
|
#include "ac3enc.c"
|
|
|
|
|
|
/** Scale a float value by 2^15, convert to an integer, and clip to range -32767..32767. */
|
|
#define FIX15(a) av_clip(SCALE_FLOAT(a, 15), -32767, 32767)
|
|
|
|
|
|
/**
|
|
* Finalize MDCT and free allocated memory.
|
|
*/
|
|
static av_cold void mdct_end(AC3MDCTContext *mdct)
|
|
{
|
|
mdct->nbits = 0;
|
|
av_freep(&mdct->costab);
|
|
av_freep(&mdct->sintab);
|
|
av_freep(&mdct->xcos1);
|
|
av_freep(&mdct->xsin1);
|
|
av_freep(&mdct->rot_tmp);
|
|
av_freep(&mdct->cplx_tmp);
|
|
}
|
|
|
|
|
|
/**
|
|
* Initialize FFT tables.
|
|
* @param ln log2(FFT size)
|
|
*/
|
|
static av_cold int fft_init(AVCodecContext *avctx, AC3MDCTContext *mdct, int ln)
|
|
{
|
|
int i, n, n2;
|
|
float alpha;
|
|
|
|
n = 1 << ln;
|
|
n2 = n >> 1;
|
|
|
|
FF_ALLOC_OR_GOTO(avctx, mdct->costab, n2 * sizeof(*mdct->costab), fft_alloc_fail);
|
|
FF_ALLOC_OR_GOTO(avctx, mdct->sintab, n2 * sizeof(*mdct->sintab), fft_alloc_fail);
|
|
|
|
for (i = 0; i < n2; i++) {
|
|
alpha = 2.0 * M_PI * i / n;
|
|
mdct->costab[i] = FIX15(cos(alpha));
|
|
mdct->sintab[i] = FIX15(sin(alpha));
|
|
}
|
|
|
|
return 0;
|
|
fft_alloc_fail:
|
|
mdct_end(mdct);
|
|
return AVERROR(ENOMEM);
|
|
}
|
|
|
|
|
|
/**
|
|
* Initialize MDCT tables.
|
|
* @param nbits log2(MDCT size)
|
|
*/
|
|
static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
|
|
int nbits)
|
|
{
|
|
int i, n, n4, ret;
|
|
|
|
n = 1 << nbits;
|
|
n4 = n >> 2;
|
|
|
|
mdct->nbits = nbits;
|
|
|
|
ret = fft_init(avctx, mdct, nbits - 2);
|
|
if (ret)
|
|
return ret;
|
|
|
|
mdct->window = ff_ac3_window;
|
|
|
|
FF_ALLOC_OR_GOTO(avctx, mdct->xcos1, n4 * sizeof(*mdct->xcos1), mdct_alloc_fail);
|
|
FF_ALLOC_OR_GOTO(avctx, mdct->xsin1, n4 * sizeof(*mdct->xsin1), mdct_alloc_fail);
|
|
FF_ALLOC_OR_GOTO(avctx, mdct->rot_tmp, n * sizeof(*mdct->rot_tmp), mdct_alloc_fail);
|
|
FF_ALLOC_OR_GOTO(avctx, mdct->cplx_tmp, n4 * sizeof(*mdct->cplx_tmp), mdct_alloc_fail);
|
|
|
|
for (i = 0; i < n4; i++) {
|
|
float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n;
|
|
mdct->xcos1[i] = FIX15(-cos(alpha));
|
|
mdct->xsin1[i] = FIX15(-sin(alpha));
|
|
}
|
|
|
|
return 0;
|
|
mdct_alloc_fail:
|
|
mdct_end(mdct);
|
|
return AVERROR(ENOMEM);
|
|
}
|
|
|
|
|
|
/** Butterfly op */
|
|
#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
|
|
{ \
|
|
int ax, ay, bx, by; \
|
|
bx = pre1; \
|
|
by = pim1; \
|
|
ax = qre1; \
|
|
ay = qim1; \
|
|
pre = (bx + ax) >> 1; \
|
|
pim = (by + ay) >> 1; \
|
|
qre = (bx - ax) >> 1; \
|
|
qim = (by - ay) >> 1; \
|
|
}
|
|
|
|
|
|
/** Complex multiply */
|
|
#define CMUL(pre, pim, are, aim, bre, bim) \
|
|
{ \
|
|
pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15; \
|
|
pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15; \
|
|
}
|
|
|
|
|
|
/**
|
|
* Calculate a 2^n point complex FFT on 2^ln points.
|
|
* @param z complex input/output samples
|
|
* @param ln log2(FFT size)
|
|
*/
|
|
static void fft(AC3MDCTContext *mdct, IComplex *z, int ln)
|
|
{
|
|
int j, l, np, np2;
|
|
int nblocks, nloops;
|
|
register IComplex *p,*q;
|
|
int tmp_re, tmp_im;
|
|
|
|
np = 1 << ln;
|
|
|
|
/* reverse */
|
|
for (j = 0; j < np; j++) {
|
|
int k = av_reverse[j] >> (8 - ln);
|
|
if (k < j)
|
|
FFSWAP(IComplex, z[k], z[j]);
|
|
}
|
|
|
|
/* pass 0 */
|
|
|
|
p = &z[0];
|
|
j = np >> 1;
|
|
do {
|
|
BF(p[0].re, p[0].im, p[1].re, p[1].im,
|
|
p[0].re, p[0].im, p[1].re, p[1].im);
|
|
p += 2;
|
|
} while (--j);
|
|
|
|
/* pass 1 */
|
|
|
|
p = &z[0];
|
|
j = np >> 2;
|
|
do {
|
|
BF(p[0].re, p[0].im, p[2].re, p[2].im,
|
|
p[0].re, p[0].im, p[2].re, p[2].im);
|
|
BF(p[1].re, p[1].im, p[3].re, p[3].im,
|
|
p[1].re, p[1].im, p[3].im, -p[3].re);
|
|
p+=4;
|
|
} while (--j);
|
|
|
|
/* pass 2 .. ln-1 */
|
|
|
|
nblocks = np >> 3;
|
|
nloops = 1 << 2;
|
|
np2 = np >> 1;
|
|
do {
|
|
p = z;
|
|
q = z + nloops;
|
|
for (j = 0; j < nblocks; j++) {
|
|
BF(p->re, p->im, q->re, q->im,
|
|
p->re, p->im, q->re, q->im);
|
|
p++;
|
|
q++;
|
|
for(l = nblocks; l < np2; l += nblocks) {
|
|
CMUL(tmp_re, tmp_im, mdct->costab[l], -mdct->sintab[l], q->re, q->im);
|
|
BF(p->re, p->im, q->re, q->im,
|
|
p->re, p->im, tmp_re, tmp_im);
|
|
p++;
|
|
q++;
|
|
}
|
|
p += nloops;
|
|
q += nloops;
|
|
}
|
|
nblocks = nblocks >> 1;
|
|
nloops = nloops << 1;
|
|
} while (nblocks);
|
|
}
|
|
|
|
|
|
/**
|
|
* Calculate a 512-point MDCT
|
|
* @param out 256 output frequency coefficients
|
|
* @param in 512 windowed input audio samples
|
|
*/
|
|
static void mdct512(AC3MDCTContext *mdct, int32_t *out, int16_t *in)
|
|
{
|
|
int i, re, im, n, n2, n4;
|
|
int16_t *rot = mdct->rot_tmp;
|
|
IComplex *x = mdct->cplx_tmp;
|
|
|
|
n = 1 << mdct->nbits;
|
|
n2 = n >> 1;
|
|
n4 = n >> 2;
|
|
|
|
/* shift to simplify computations */
|
|
for (i = 0; i <n4; i++)
|
|
rot[i] = -in[i + 3*n4];
|
|
memcpy(&rot[n4], &in[0], 3*n4*sizeof(*in));
|
|
|
|
/* pre rotation */
|
|
for (i = 0; i < n4; i++) {
|
|
re = ((int)rot[ 2*i] - (int)rot[ n-1-2*i]) >> 1;
|
|
im = -((int)rot[n2+2*i] - (int)rot[n2-1-2*i]) >> 1;
|
|
CMUL(x[i].re, x[i].im, re, im, -mdct->xcos1[i], mdct->xsin1[i]);
|
|
}
|
|
|
|
fft(mdct, x, mdct->nbits - 2);
|
|
|
|
/* post rotation */
|
|
for (i = 0; i < n4; i++) {
|
|
re = x[i].re;
|
|
im = x[i].im;
|
|
CMUL(out[n2-1-2*i], out[2*i], re, im, mdct->xsin1[i], mdct->xcos1[i]);
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Apply KBD window to input samples prior to MDCT.
|
|
*/
|
|
static void apply_window(DSPContext *dsp, int16_t *output, const int16_t *input,
|
|
const int16_t *window, int n)
|
|
{
|
|
int i;
|
|
int n2 = n >> 1;
|
|
|
|
for (i = 0; i < n2; i++) {
|
|
output[i] = MUL16(input[i], window[i]) >> 15;
|
|
output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15;
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Calculate the log2() of the maximum absolute value in an array.
|
|
* @param tab input array
|
|
* @param n number of values in the array
|
|
* @return log2(max(abs(tab[])))
|
|
*/
|
|
static int log2_tab(int16_t *tab, int n)
|
|
{
|
|
int i, v;
|
|
|
|
v = 0;
|
|
for (i = 0; i < n; i++)
|
|
v |= abs(tab[i]);
|
|
|
|
return av_log2(v);
|
|
}
|
|
|
|
|
|
/**
|
|
* Left-shift each value in an array by a specified amount.
|
|
* @param tab input array
|
|
* @param n number of values in the array
|
|
* @param lshift left shift amount. a negative value means right shift.
|
|
*/
|
|
static void lshift_tab(int16_t *tab, int n, int lshift)
|
|
{
|
|
int i;
|
|
|
|
if (lshift > 0) {
|
|
for (i = 0; i < n; i++)
|
|
tab[i] <<= lshift;
|
|
} else if (lshift < 0) {
|
|
lshift = -lshift;
|
|
for (i = 0; i < n; i++)
|
|
tab[i] >>= lshift;
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Normalize the input samples to use the maximum available precision.
|
|
* This assumes signed 16-bit input samples. Exponents are reduced by 9 to
|
|
* match the 24-bit internal precision for MDCT coefficients.
|
|
*
|
|
* @return exponent shift
|
|
*/
|
|
static int normalize_samples(AC3EncodeContext *s)
|
|
{
|
|
int v = 14 - log2_tab(s->windowed_samples, AC3_WINDOW_SIZE);
|
|
v = FFMAX(0, v);
|
|
lshift_tab(s->windowed_samples, AC3_WINDOW_SIZE, v);
|
|
return v - 9;
|
|
}
|
|
|
|
|
|
/**
|
|
* Scale MDCT coefficients from float to fixed-point.
|
|
*/
|
|
static void scale_coefficients(AC3EncodeContext *s)
|
|
{
|
|
/* scaling/conversion is obviously not needed for the fixed-point encoder
|
|
since the coefficients are already fixed-point. */
|
|
return;
|
|
}
|
|
|
|
|
|
#ifdef TEST
|
|
/*************************************************************************/
|
|
/* TEST */
|
|
|
|
#include "libavutil/lfg.h"
|
|
|
|
#define MDCT_NBITS 9
|
|
#define MDCT_SAMPLES (1 << MDCT_NBITS)
|
|
#define FN (MDCT_SAMPLES/4)
|
|
|
|
|
|
static void fft_test(AC3MDCTContext *mdct, AVLFG *lfg)
|
|
{
|
|
IComplex in[FN], in1[FN];
|
|
int k, n, i;
|
|
float sum_re, sum_im, a;
|
|
|
|
for (i = 0; i < FN; i++) {
|
|
in[i].re = av_lfg_get(lfg) % 65535 - 32767;
|
|
in[i].im = av_lfg_get(lfg) % 65535 - 32767;
|
|
in1[i] = in[i];
|
|
}
|
|
fft(mdct, in, 7);
|
|
|
|
/* do it by hand */
|
|
for (k = 0; k < FN; k++) {
|
|
sum_re = 0;
|
|
sum_im = 0;
|
|
for (n = 0; n < FN; n++) {
|
|
a = -2 * M_PI * (n * k) / FN;
|
|
sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
|
|
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
|
|
}
|
|
av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n",
|
|
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
|
|
}
|
|
}
|
|
|
|
|
|
static void mdct_test(AC3MDCTContext *mdct, AVLFG *lfg)
|
|
{
|
|
int16_t input[MDCT_SAMPLES];
|
|
int32_t output[AC3_MAX_COEFS];
|
|
float input1[MDCT_SAMPLES];
|
|
float output1[AC3_MAX_COEFS];
|
|
float s, a, err, e, emax;
|
|
int i, k, n;
|
|
|
|
for (i = 0; i < MDCT_SAMPLES; i++) {
|
|
input[i] = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10;
|
|
input1[i] = input[i];
|
|
}
|
|
|
|
mdct512(mdct, output, input);
|
|
|
|
/* do it by hand */
|
|
for (k = 0; k < AC3_MAX_COEFS; k++) {
|
|
s = 0;
|
|
for (n = 0; n < MDCT_SAMPLES; n++) {
|
|
a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES));
|
|
s += input1[n] * cos(a);
|
|
}
|
|
output1[k] = -2 * s / MDCT_SAMPLES;
|
|
}
|
|
|
|
err = 0;
|
|
emax = 0;
|
|
for (i = 0; i < AC3_MAX_COEFS; i++) {
|
|
av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]);
|
|
e = output[i] - output1[i];
|
|
if (e > emax)
|
|
emax = e;
|
|
err += e * e;
|
|
}
|
|
av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax);
|
|
}
|
|
|
|
|
|
int main(void)
|
|
{
|
|
AVLFG lfg;
|
|
AC3MDCTContext mdct;
|
|
|
|
mdct.avctx = NULL;
|
|
av_log_set_level(AV_LOG_DEBUG);
|
|
mdct_init(&mdct, 9);
|
|
|
|
fft_test(&mdct, &lfg);
|
|
mdct_test(&mdct, &lfg);
|
|
|
|
return 0;
|
|
}
|
|
#endif /* TEST */
|
|
|
|
|
|
AVCodec ac3_fixed_encoder = {
|
|
"ac3_fixed",
|
|
AVMEDIA_TYPE_AUDIO,
|
|
CODEC_ID_AC3,
|
|
sizeof(AC3EncodeContext),
|
|
ac3_encode_init,
|
|
ac3_encode_frame,
|
|
ac3_encode_close,
|
|
NULL,
|
|
.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
|
|
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
|
|
.channel_layouts = ac3_channel_layouts,
|
|
};
|