[Ffmpeg-devel] Patch DURATION_MAX_READ_SIZE in lavf/utils.c

[Måns Rullgård]

Fred Rothganger <rothgang at uiuc.edu> writes:

>>i think you should add a comment to the #define so the reader knows why
>>its the value it is
>>making it user setable would be interrsting too ...
>>
>>
>
>     Here's another attempt.
>
> -- Fred
> Index: utils.c
> ===================================================================
> RCS file: /cvsroot/ffmpeg/ffmpeg/libavformat/utils.c,v
> retrieving revision 1.164
> diff -u -r1.164 utils.c
> --- utils.c	15 Aug 2005 15:58:21 -0000	1.164
> +++ utils.c	2 Sep 2005 20:01:27 -0000
> @@ -1613,7 +1613,13 @@
>      }
>  }
>
> -#define DURATION_MAX_READ_SIZE 250000
> +/*
> +  The following constant limits how many bytes to read at the beginning
> +  and end of an MPEG file while searching for PTS info.  The number should
> +  be large enough so that at least one packet (having a PTS) of each stream
> +  will be seen at each end of the file.
> + */
> +#define DURATION_MAX_READ_SIZE 500000

FWIW, an MP at ML MPEG2 video (max 15Mbps) can have as many as 1312500
bytes of elementary stream data between PTS values, not counting PS/TS
overhead.  Of course, if an audio stream is present, PTS values will
be much more frequent (in terms of byte position).

-- 
M?ns Rullg?rd
mru at inprovide.com