[FFmpeg-soc] [soc]: r4533 - seek_api/parser.c

[zhentan feng]

Hi

2009/6/30 Baptiste Coudurier <baptiste.coudurier at gmail.com>

> Hi Zhentan,
>
> zhentan feng wrote:
> > Hi
> >
> > 2009/6/29 Baptiste Coudurier <baptiste.coudurier at 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.
>

fixed , please see r4550 patch.

>
> [...]




-- 
Best wishes~