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/*
* MPEG Audio parser
* Copyright (c) 2003 Fabrice Bellard.
* Copyright (c) 2003 Michael Niedermayer.
*
* 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
*/
#include "parser.h"
#include "mpegaudio.h"
#include "mpegaudiodecheader.h"
typedef struct MpegAudioParseContext {
uint8_t inbuf[MPA_MAX_CODED_FRAME_SIZE]; /* input buffer */
uint8_t *inbuf_ptr;
int frame_size;
int free_format_frame_size;
int free_format_next_header;
uint32_t header;
int header_count;
} MpegAudioParseContext;
#define MPA_HEADER_SIZE 4
/* header + layer + bitrate + freq + lsf/mpeg25 */
#undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
#define SAME_HEADER_MASK \
(0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
/* useful helper to get mpeg audio stream infos. Return -1 if error in
header, otherwise the coded frame size in bytes */
int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate)
{
MPADecodeContext s1, *s = &s1;
s1.avctx = avctx;
if (ff_mpa_check_header(head) != 0)
return -1;
if (ff_mpegaudio_decode_header(s, head) != 0) {
return -1;
}
switch(s->layer) {
case 1:
avctx->frame_size = 384;
break;
case 2:
avctx->frame_size = 1152;
break;
default:
case 3:
if (s->lsf)
avctx->frame_size = 576;
else
avctx->frame_size = 1152;
break;
}
*sample_rate = s->sample_rate;
avctx->channels = s->nb_channels;
avctx->bit_rate = s->bit_rate;
avctx->sub_id = s->layer;
return s->frame_size;
}
static int mpegaudio_parse_init(AVCodecParserContext *s1)
{
MpegAudioParseContext *s = s1->priv_data;
s->inbuf_ptr = s->inbuf;
return 0;
}
static int mpegaudio_parse(AVCodecParserContext *s1,
AVCodecContext *avctx,
const uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size)
{
MpegAudioParseContext *s = s1->priv_data;
int len, ret, sr;
uint32_t header;
const uint8_t *buf_ptr;
*poutbuf = NULL;
*poutbuf_size = 0;
buf_ptr = buf;
while (buf_size > 0) {
len = s->inbuf_ptr - s->inbuf;
if (s->frame_size == 0) {
/* special case for next header for first frame in free
format case (XXX: find a simpler method) */
if (s->free_format_next_header != 0) {
AV_WB32(s->inbuf, s->free_format_next_header);
s->inbuf_ptr = s->inbuf + 4;
s->free_format_next_header = 0;
goto got_header;
}
/* no header seen : find one. We need at least MPA_HEADER_SIZE
bytes to parse it */
len = FFMIN(MPA_HEADER_SIZE - len, buf_size);
if (len > 0) {
memcpy(s->inbuf_ptr, buf_ptr, len);
buf_ptr += len;
buf_size -= len;
s->inbuf_ptr += len;
}
if ((s->inbuf_ptr - s->inbuf) >= MPA_HEADER_SIZE) {
got_header:
header = AV_RB32(s->inbuf);
ret = ff_mpa_decode_header(avctx, header, &sr);
if (ret < 0) {
s->header_count= -2;
/* no sync found : move by one byte (inefficient, but simple!) */
memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
s->inbuf_ptr--;
dprintf(avctx, "skip %x\n", header);
/* reset free format frame size to give a chance
to get a new bitrate */
s->free_format_frame_size = 0;
} else {
if((header&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
s->header_count= -3;
s->header= header;
s->header_count++;
s->frame_size = ret;
#if 0
/* free format: prepare to compute frame size */
if (ff_mpegaudio_decode_header(s, header) == 1) {
s->frame_size = -1;
}
#endif
if(s->header_count > 1)
avctx->sample_rate= sr;
}
}
} else
#if 0
if (s->frame_size == -1) {
/* free format : find next sync to compute frame size */
len = MPA_MAX_CODED_FRAME_SIZE - len;
if (len > buf_size)
len = buf_size;
if (len == 0) {
/* frame too long: resync */
s->frame_size = 0;
memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
s->inbuf_ptr--;
} else {
uint8_t *p, *pend;
uint32_t header1;
int padding;
memcpy(s->inbuf_ptr, buf_ptr, len);
/* check for header */
p = s->inbuf_ptr - 3;
pend = s->inbuf_ptr + len - 4;
while (p <= pend) {
header = AV_RB32(p);
header1 = AV_RB32(s->inbuf);
/* check with high probability that we have a
valid header */
if ((header & SAME_HEADER_MASK) ==
(header1 & SAME_HEADER_MASK)) {
/* header found: update pointers */
len = (p + 4) - s->inbuf_ptr;
buf_ptr += len;
buf_size -= len;
s->inbuf_ptr = p;
/* compute frame size */
s->free_format_next_header = header;
s->free_format_frame_size = s->inbuf_ptr - s->inbuf;
padding = (header1 >> 9) & 1;
if (s->layer == 1)
s->free_format_frame_size -= padding * 4;
else
s->free_format_frame_size -= padding;
dprintf(avctx, "free frame size=%d padding=%d\n",
s->free_format_frame_size, padding);
ff_mpegaudio_decode_header(s, header1);
goto next_data;
}
p++;
}
/* not found: simply increase pointers */
buf_ptr += len;
s->inbuf_ptr += len;
buf_size -= len;
}
} else
#endif
if (len < s->frame_size) {
if (s->frame_size > MPA_MAX_CODED_FRAME_SIZE)
s->frame_size = MPA_MAX_CODED_FRAME_SIZE;
len = FFMIN(s->frame_size - len, buf_size);
memcpy(s->inbuf_ptr, buf_ptr, len);
buf_ptr += len;
s->inbuf_ptr += len;
buf_size -= len;
}
if(s->frame_size > 0 && buf_ptr - buf == s->inbuf_ptr - s->inbuf
&& buf_size + buf_ptr - buf >= s->frame_size){
if(s->header_count > 0){
*poutbuf = buf;
*poutbuf_size = s->frame_size;
}
buf_ptr = buf + s->frame_size;
s->inbuf_ptr = s->inbuf;
s->frame_size = 0;
break;
}
// next_data:
if (s->frame_size > 0 &&
(s->inbuf_ptr - s->inbuf) >= s->frame_size) {
if(s->header_count > 0){
*poutbuf = s->inbuf;
*poutbuf_size = s->inbuf_ptr - s->inbuf;
}
s->inbuf_ptr = s->inbuf;
s->frame_size = 0;
break;
}
}
return buf_ptr - buf;
}
AVCodecParser mpegaudio_parser = {
{ CODEC_ID_MP2, CODEC_ID_MP3 },
sizeof(MpegAudioParseContext),
mpegaudio_parse_init,
mpegaudio_parse,
NULL,
};
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