mirror of https://git.ffmpeg.org/ffmpeg.git
118 lines
2.9 KiB
C
118 lines
2.9 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
|
|
* floating-point AC-3 encoder.
|
|
*/
|
|
|
|
#define CONFIG_AC3ENC_FLOAT 1
|
|
#include "ac3enc.c"
|
|
|
|
|
|
/**
|
|
* Finalize MDCT and free allocated memory.
|
|
*/
|
|
static av_cold void mdct_end(AC3MDCTContext *mdct)
|
|
{
|
|
ff_mdct_end(&mdct->fft);
|
|
av_freep(&mdct->window);
|
|
}
|
|
|
|
|
|
/**
|
|
* Initialize MDCT tables.
|
|
* @param nbits log2(MDCT size)
|
|
*/
|
|
static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
|
|
int nbits)
|
|
{
|
|
float *window;
|
|
int n, n2;
|
|
|
|
n = 1 << nbits;
|
|
n2 = n >> 1;
|
|
|
|
window = av_malloc(n2 * sizeof(*window));
|
|
if (!window) {
|
|
av_log(avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
|
|
return AVERROR(ENOMEM);
|
|
}
|
|
ff_kbd_window_init(window, 5.0, n2);
|
|
mdct->window = window;
|
|
|
|
return ff_mdct_init(&mdct->fft, nbits, 0, -2.0 / n);
|
|
}
|
|
|
|
|
|
/**
|
|
* Calculate a 512-point MDCT
|
|
* @param out 256 output frequency coefficients
|
|
* @param in 512 windowed input audio samples
|
|
*/
|
|
static void mdct512(AC3MDCTContext *mdct, float *out, float *in)
|
|
{
|
|
ff_mdct_calc(&mdct->fft, out, in);
|
|
}
|
|
|
|
|
|
/**
|
|
* Apply KBD window to input samples prior to MDCT.
|
|
*/
|
|
static void apply_window(float *output, const float *input,
|
|
const float *window, int n)
|
|
{
|
|
int i;
|
|
int n2 = n >> 1;
|
|
|
|
for (i = 0; i < n2; i++) {
|
|
output[i] = input[i] * window[i];
|
|
output[n-i-1] = input[n-i-1] * window[i];
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Normalize the input samples to use the maximum available precision.
|
|
*/
|
|
static int normalize_samples(AC3EncodeContext *s)
|
|
{
|
|
/* Normalization is not needed for floating-point samples, so just return 0 */
|
|
return 0;
|
|
}
|
|
|
|
|
|
AVCodec ac3_encoder = {
|
|
"ac3",
|
|
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_FLT,AV_SAMPLE_FMT_NONE},
|
|
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
|
|
.channel_layouts = ac3_channel_layouts,
|
|
};
|