mirror of https://git.ffmpeg.org/ffmpeg.git
120 lines
3.2 KiB
C
120 lines
3.2 KiB
C
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/*
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* copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz>
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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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* AAC LATM parser
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <sys/types.h>
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#include "parser.h"
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#define LATM_HEADER 0x56e000 // 0x2b7 (11 bits)
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#define LATM_MASK 0xFFE000 // top 11 bits
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#define LATM_SIZE_MASK 0x001FFF // bottom 13 bits
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typedef struct LATMParseContext{
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ParseContext pc;
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int count;
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} LATMParseContext;
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/**
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* finds the end of the current frame in the bitstream.
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* @return the position of the first byte of the next frame, or -1
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*/
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static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf,
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int buf_size)
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{
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LATMParseContext *s = s1->priv_data;
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ParseContext *pc = &s->pc;
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int pic_found, i;
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uint32_t state;
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pic_found = pc->frame_start_found;
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state = pc->state;
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i = 0;
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if (!pic_found) {
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for (i = 0; i < buf_size; i++) {
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state = (state<<8) | buf[i];
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if ((state & LATM_MASK) == LATM_HEADER) {
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i++;
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s->count = -i;
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pic_found = 1;
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break;
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}
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}
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}
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if (pic_found) {
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/* EOF considered as end of frame */
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if (buf_size == 0)
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return 0;
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if ((state & LATM_SIZE_MASK) - s->count <= buf_size) {
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pc->frame_start_found = 0;
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pc->state = -1;
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return (state & LATM_SIZE_MASK) - s->count;
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}
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}
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s->count += buf_size;
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pc->frame_start_found = pic_found;
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pc->state = state;
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return END_NOT_FOUND;
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}
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static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
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const uint8_t **poutbuf, int *poutbuf_size,
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const uint8_t *buf, int buf_size)
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{
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LATMParseContext *s = s1->priv_data;
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ParseContext *pc = &s->pc;
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int next;
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if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
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next = buf_size;
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} else {
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next = latm_find_frame_end(s1, buf, buf_size);
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if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
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*poutbuf = NULL;
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*poutbuf_size = 0;
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return buf_size;
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}
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}
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*poutbuf = buf;
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*poutbuf_size = buf_size;
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return next;
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}
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AVCodecParser aac_latm_parser = {
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{ CODEC_ID_AAC_LATM },
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sizeof(LATMParseContext),
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NULL,
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latm_parse,
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ff_parse_close
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};
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