[MPlayer-dev-eng] PATCH: Fixes seeking based on percentage for mpg's with timestamps not starting at 0

[Nico Sabbi]

elupus wrote:

>Hi, 
>
>Not sure if you guys are interested, but i'll check anyways. This patch
>attempts to fix seeking based on percentage of total time in mpgs that has
>timesstamps that doesn't start from 0. (I can provide a sample should that
>be needed). A variant of this patch has been implemented in xbmc's variant
>of mplayer to allow current playtime to be reported correctly and seeking by
>percentage to work. As it is now, seeking by percentage in such a file just
>makes end of file to be reached directly.
>
>It attempts to fix this by remembering what the pts value (timestamp) found
>when buffer is filled for the first time. This is based on that value of
>mpg->last_pts, i suppose this really should be offset with the current
>buffer size as even proper mpg's report a nonzero value here(allthough
>small).  
>
>This value can then also be used by the OSD to offset sh_video->pts to
>display current playtime, but i didn't include that part in the patch as
>that isn't done very cleanly in the current version used in xbmc mplayer. 
>
>Ts/ty files suffer from the same problem at times (atleast the time
>reported, haven't seen issued with seeking), so something similar should
>probably be implemented in those demuxer too. 
>
>Anyway, as mplayer normally doesn't seek by percentage and the current
>playtime is't really used for anything important, this patch isn't that
>important. But I thought it might be interesting nontheless.
>
>Regards
>elupus Team XBMC
>  
>

Hi,

 >          if (mpg_d->final_pts > 0.0)
 >-            newpos += rel_seek_secs * (demuxer->movi_end - 
demuxer->movi_start) / mpg_d->final_pts;
 >+            newpos += rel_seek_secs * (demuxer->movi_end - 
demuxer->movi_start) / (mpg_d->final_pts - firstpts);
 >           else if (oldpts > 0.0)
 >-            newpos += rel_seek_secs * (oldpos - demuxer->movi_start) 
/ oldpts;
 >+            newpos += rel_seek_secs * (oldpos - demuxer->movi_start) 
/ (oldpts - firstpts);

I don't understand what guarantees that (mpg_d->final_pts - firstpts) > 
0 and (oldpts - firstpts).

    Nico