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![Michael Niedermayer](/assets/img/avatar_default.png)
of calling it at the end of a frame with a large negative offset. This significantly reduces the maximal distance in container packets between the point where the first byte of the "access unit" was stored and where we call ff_fetch_timestamp() thus reducing the constraints on our parser. Also change the parser from next_frame_offset to cur, this is needed because now the reference is from container packet start instead of frame start. (i previously misinterpreted this as bug) Originally committed as revision 17731 to svn://svn.ffmpeg.org/ffmpeg/trunk
181 lines
6.8 KiB
C
181 lines
6.8 KiB
C
/*
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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 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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#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;
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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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//FIXME replace the crap with get_bits()
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s->repeat_pict = 0;
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buf_end = buf + buf_size;
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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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avcodec_set_dimensions(avctx, pc->width, pc->height);
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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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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 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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};
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