Hi Zhentan, zhentan feng wrote: > Hi > > 2009/6/29 Baptiste Coudurier <baptiste.coudur...@gmail.com> > >> spyfeng wrote: >>> Author: spyfeng >>> Date: Sat Jun 27 15:35:59 2009 >>> New Revision: 4533 >>> >>> Log: >>> set correct pos when cannot get pos from ff_fetch_timestamp(). >>> >>> Modified: >>> seek_api/parser.c >>> >>> Modified: seek_api/parser.c >>> >> ============================================================================== >>> --- seek_api/parser.c Sat Jun 27 15:28:08 2009 (r4532) >>> +++ seek_api/parser.c Sat Jun 27 15:35:59 2009 (r4533) >>> @@ -188,6 +188,8 @@ int av_parser_parse2(AVCodecParserContex >>> if (index < 0) >>> index = 0; >>> s->cur_offset += index; >>> + if (s->pos == -1) >>> + s->pos = s->last_pos + index; >>> return index; >>> } >> Can you explain why this change is needed ? It seems wrong to me. >> >> The goal is for getting the correct pkt->pos when call av_read_frame(). > > consider the attached two log files below. I added some log info when > av_parser_parse2() is called in libavformait/utils.c > logpf2.txt is the original outputs and logpf3.txt is the new outputs. > > I select some lines from logf2.txt. > for example, the first frame of stream index = 1 is: > [mpeg @ 0x9c43440]av_read_frame_internal stream=1, pts=45000, dts=45000, > size=208, flags=1, pos=2048 > > then the second frame is > [mpeg @ 0x9c43440]av_read_frame_internal stream=1, pts=47351, dts=47351, > size=209, flags=1, pos=-1 > > actually, we can calculate the second frame pos by the last_pos. > If keep the frame as -1, when find the keyframe by index entries, the index > entries pos is -1, we cannot seek there.
Yes, pos must be set to the PES packet pos to be able to seek there and retrieve correct pts/dts for the frame. Example below: > > > ------------------------------------------------------------------------ > > Input #0, mpeg, from 'tests/data/b-lavf.mpg': > Duration: 00:00:01.01, start: 0.500000, bitrate: 2975 kb/s > Stream #0.0[0x1e0], 1/90000: Video: mpeg1video, yuv420p, 352x288 [PAR 1:1 > DAR 11:9], 1/25, 104857 kb/s, 25 tbr, 90k tbn, 25 tbc > Stream #0.1[0x1c0], 1/90000: Audio: mp2, 44100 Hz, mono, s16, 64 kb/s > Output #0, null, to '/dev/null': > Stream #0.0, 1/90000: Video: rawvideo, yuv420p, 352x288 [PAR 1:1 DAR > 11:9], 1/25, q=2-31, 200 kb/s, 90k tbn, 25 tbc > Stream #0.1, 1/90000: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s > Stream mapping: > Stream #0.0 -> #0.0 > Stream #0.1 -> #0.1 > Press [q] to stop encoding > [mpeg @ 0x9c43440]mpeg add index stream_index=0, pos = 30, dts = 41400 > [mpeg @ 0x9c43440]av_read_packet stream=0, pts=45000, dts=41400, size=2002, > flags=0, pos = 30 > [mpeg @ 0x9c43440]mpeg add index stream_index=1, pos = 2048, dts = 45000 > [mpeg @ 0x9c43440]av_read_packet stream=1, pts=45000, dts=45000, size=2037, > flags=0, pos = 2048 pos is set here. > [mpeg @ 0x9c43440]pkt pos:2048, st->parser->pos:2048 > [mpeg @ 0x9c43440]stream_index 1, the frame_offset = 2048 > [mpeg @ 0x9c43440]av_read_frame_internal stream=1, pts=45000, dts=45000, > size=208, flags=1, pos=2048 > [mpeg @ 0x9c43440]pkt pos:-1, st->parser->pos:-1 > [mpeg @ 0x9c43440]stream_index 1, the frame_offset = 2256 > [mpeg @ 0x9c43440]av_read_frame_internal stream=1, pts=47351, dts=47351, > size=209, flags=1, pos=-1 > [mpeg @ 0x9c43440]pkt pos:-1, st->parser->pos:-1 > [mpeg @ 0x9c43440]stream_index 1, the frame_offset = 2465 Pos must be 2048 as well. [...] -- Baptiste COUDURIER GnuPG Key Id: 0x5C1ABAAA Key fingerprint 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA FFmpeg maintainer http://www.ffmpeg.org _______________________________________________ FFmpeg-soc mailing list FFmpeg-soc@mplayerhq.hu https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-soc
