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ffmpeg / libavcodec / h261_parser.c @ 2912e87a

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/*
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 * H261 parser
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 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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 * Copyright (c) 2004 Maarten Daniels
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 *
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 * This file is part of Libav.
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 *
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 * Libav 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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 * Libav 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 Libav; 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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 * h261codec.
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 */
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#include "parser.h"
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static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
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    int vop_found, i, j;
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    uint32_t state;
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    vop_found= pc->frame_start_found;
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    state= pc->state;
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    for(i=0; i<buf_size && !vop_found; i++){
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        state= (state<<8) | buf[i];
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        for(j=0; j<8; j++){
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            if(((state>>j)&0xFFFFF0) == 0x000100){
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                vop_found=1;
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                break;
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            }
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        }
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    }
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    if(vop_found){
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        for(; i<buf_size; i++){
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            state= (state<<8) | buf[i];
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            for(j=0; j<8; j++){
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                if(((state>>j)&0xFFFFF0) == 0x000100){
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                    pc->frame_start_found=0;
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                    pc->state= (state>>(3*8))+0xFF00;
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                    return i-2;
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                }
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            }
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        }
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    }
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    pc->frame_start_found= vop_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 h261_parse(AVCodecParserContext *s,
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                      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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    ParseContext *pc = s->priv_data;
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    int next;
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    next= h261_find_frame_end(pc,avctx, 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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    *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 ff_h261_parser = {
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    { CODEC_ID_H261 },
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    sizeof(ParseContext),
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    NULL,
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    h261_parse,
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    ff_parse_close,
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};