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ffmpeg / libavcodec / mpegvideo_parser.c @ 2912e87a

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/*
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 * MPEG1 / MPEG2 video parser
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 * Copyright (c) 2000,2001 Fabrice Bellard
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 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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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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#include "parser.h"
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#include "mpegvideo.h"
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static void mpegvideo_extract_headers(AVCodecParserContext *s,
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                                      AVCodecContext *avctx,
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                                      const uint8_t *buf, int buf_size)
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{
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    ParseContext1 *pc = s->priv_data;
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    const uint8_t *buf_end = buf + buf_size;
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    uint32_t start_code;
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    int frame_rate_index, ext_type, bytes_left;
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    int frame_rate_ext_n, frame_rate_ext_d;
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    int picture_structure, top_field_first, repeat_first_field, progressive_frame;
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    int horiz_size_ext, vert_size_ext, bit_rate_ext;
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    int did_set_size=0;
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//FIXME replace the crap with get_bits()
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    s->repeat_pict = 0;
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    while (buf < buf_end) {
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        start_code= -1;
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        buf= ff_find_start_code(buf, buf_end, &start_code);
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        bytes_left = buf_end - buf;
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        switch(start_code) {
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        case PICTURE_START_CODE:
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            if (bytes_left >= 2) {
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                s->pict_type = (buf[1] >> 3) & 7;
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            }
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            break;
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        case SEQ_START_CODE:
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            if (bytes_left >= 7) {
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                pc->width  = (buf[0] << 4) | (buf[1] >> 4);
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                pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
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                if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
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                    avcodec_set_dimensions(avctx, pc->width, pc->height);
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                    did_set_size=1;
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                }
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                frame_rate_index = buf[3] & 0xf;
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                pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
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                pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
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                avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
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                avctx->codec_id = CODEC_ID_MPEG1VIDEO;
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                avctx->sub_id = 1;
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            }
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            break;
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        case EXT_START_CODE:
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            if (bytes_left >= 1) {
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                ext_type = (buf[0] >> 4);
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                switch(ext_type) {
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                case 0x1: /* sequence extension */
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                    if (bytes_left >= 6) {
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                        horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
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                        vert_size_ext = (buf[2] >> 5) & 3;
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                        bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
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                        frame_rate_ext_n = (buf[5] >> 5) & 3;
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                        frame_rate_ext_d = (buf[5] & 0x1f);
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                        pc->progressive_sequence = buf[1] & (1 << 3);
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                        avctx->has_b_frames= !(buf[5] >> 7);
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                        pc->width  |=(horiz_size_ext << 12);
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                        pc->height |=( vert_size_ext << 12);
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                        avctx->bit_rate += (bit_rate_ext << 18) * 400;
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                        if(did_set_size)
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                            avcodec_set_dimensions(avctx, pc->width, pc->height);
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                        avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
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                        avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
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                        avctx->codec_id = CODEC_ID_MPEG2VIDEO;
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                        avctx->sub_id = 2; /* forces MPEG2 */
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                    }
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                    break;
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                case 0x8: /* picture coding extension */
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                    if (bytes_left >= 5) {
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                        picture_structure = buf[2]&3;
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                        top_field_first = buf[3] & (1 << 7);
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                        repeat_first_field = buf[3] & (1 << 1);
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                        progressive_frame = buf[4] & (1 << 7);
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                        /* check if we must repeat the frame */
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                        s->repeat_pict = 1;
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                        if (repeat_first_field) {
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                            if (pc->progressive_sequence) {
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                                if (top_field_first)
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                                    s->repeat_pict = 5;
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                                else
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                                    s->repeat_pict = 3;
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                            } else if (progressive_frame) {
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                                s->repeat_pict = 2;
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                            }
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                        }
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                    }
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                    break;
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                }
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            }
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            break;
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        case -1:
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            goto the_end;
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        default:
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            /* we stop parsing when we encounter a slice. It ensures
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               that this function takes a negligible amount of time */
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            if (start_code >= SLICE_MIN_START_CODE &&
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                start_code <= SLICE_MAX_START_CODE)
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                goto the_end;
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            break;
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        }
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    }
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 the_end: ;
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}
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static int mpegvideo_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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    ParseContext1 *pc1 = s->priv_data;
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    ParseContext *pc= &pc1->pc;
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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= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
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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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    /* we have a full frame : we just parse the first few MPEG headers
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       to have the full timing information. The time take by this
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       function should be negligible for uncorrupted streams */
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    mpegvideo_extract_headers(s, avctx, buf, buf_size);
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#if 0
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    printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
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           s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
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#endif
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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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static int mpegvideo_split(AVCodecContext *avctx,
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                           const uint8_t *buf, int buf_size)
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{
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    int i;
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    uint32_t state= -1;
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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 != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
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            return i-3;
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    }
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    return 0;
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}
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AVCodecParser ff_mpegvideo_parser = {
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    { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
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    sizeof(ParseContext1),
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    NULL,
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    mpegvideo_parse,
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    ff_parse1_close,
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    mpegvideo_split,
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};