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ffmpeg / libavcodec / mjpeg_parser.c @ 2912e87a

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/*
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 * MJPEG parser
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 * Copyright (c) 2000, 2001 Fabrice Bellard
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 * Copyright (c) 2003 Alex Beregszaszi
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 * Copyright (c) 2003-2004 Michael Niedermayer
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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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 * MJPEG parser.
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 */
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#include "parser.h"
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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 find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
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    int vop_found, i;
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    uint16_t state;
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    vop_found= pc->frame_start_found;
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    state= pc->state;
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    i=0;
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    if(!vop_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 == 0xFFD8){
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                i++;
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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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        /* EOF considered as end of frame */
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        if (buf_size == 0)
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            return 0;
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        for(; i<buf_size; i++){
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            state= (state<<8) | buf[i];
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            if(state == 0xFFD8){
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                pc->frame_start_found=0;
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                pc->state=0;
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                return i-1;
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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 jpeg_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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    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
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        next= buf_size;
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    }else{
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        next= find_frame_end(pc, 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 ff_mjpeg_parser = {
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    { CODEC_ID_MJPEG },
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    sizeof(ParseContext),
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    NULL,
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    jpeg_parse,
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    ff_parse_close,
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};