[MPlayer-users] -ss sometimes jumping dramatically in some mpg/mpeg2 files

[Heitzso]

I've been digging through the mplayer code to see why some -ss seeks
go bonkers in some of my video files, but not in most of them.

The problem arises from my mpg(2) files not having a pts for mplayer
to find in the last 500,000 bytes of the file.  This causes mplayer to 
fallback
to guess-timating where to seek into the file based on the video bit rate.
But mplex stuck the max bit rate into the video file header (assume, based
on other emails in transcode list) which is 9000, but that's twice the
average bit rate and therefore mplayer easily falls off the cliff (so to 
speak)
when trying to seek into the latter part of the video file.

I backed up that 500,000 to 1,000,000 and now that class of seek problem
went away.  This is any easy fix in my case because I know my video 
files are
all larger than 1,000,000 bytes.  A more elegant fix would be to insure that
we haven't pushed into a negative number.  Anyway, the fix should be
applied to demux_mpg.c, around line 110:

int demux_mpg_open (demuxer_t * demuxer) {
    stream_t *s = demuxer->stream;
    off_t pos = stream_tell (s);
    off_t end_seq_start = demuxer->movi_end - 1000000;    // 500000 is a 
wild guess

Note this is not patchable, I reformatted the C files to correct
indenting.  But the above mod is certainly simple enough for
someone to change by hand.

Note the "500000 is a wild guess".  That was certainly a clue for me.

ANYWAY,

A better code sequence would be to calculate the end_seq_start then
test to see if it is less than 0, and, if it is, to recalculate as ?? 1% 
of total
length, or some other? algorithm.  IF the powers that be would like
me to mod that one line in an official not-re-formatted version of this
file and submit a simple patch I will.  Let me know off this list and I'll
set it up and change the wild guess number at the same time.

If anyone knows why backing up to 1,000,000 char before the end and
then looking for the pts is problematic please let me know.

Thanks,
Heitzso