[vlc-devel] commit: Added hotkey code for input "frame-next". (Laurent Aimar )

[Kaarlo Räihä]

Pierre d'Herbemont kirjoitti 28.08.2009 kello 18:15:
> 
> On Aug 28, 2009, at 5:09 PM, Rémi Denis-Courmont wrote:
> 
> > Le vendredi 28 août 2009 18:06:15 Pierre d'Herbemont, vous avez  
> > écrit :
> >> On Oct 22, 2008, at 10:22 PM, git version control wrote:
> >>> vlc | branch: master | Laurent Aimar <fenrir at videolan.org> | Mon Oct
> >>> 13 23:15:00 2008 +0200| [321e04ca2733320670bada94ae1b12e0e9ceb046] |
> >>> committer: Laurent Aimar
> >>>
> >>> Added hotkey code for input "frame-next".
> >>
> >> What kind of limitation prevents us from having "frame-previous"?
> >
> > Of course, there is no limitation at the hotkey layer but...
> >
> > Many modern codecs don't support backward playback. The input code  
> > does not
> > support it.
> 
> I was wondering if there could be some kind of emulation at the input  
> code level. ie - seek back to the right(!?) frame, and then frame next  
> to find the frame we want. Easy to say... No idea if this is realistic/ 
> easy.
> 

It can be added in theory, but there would be certain problems. Like said earlier codec frame access is very problematic (I, P and B frames), because in worst case scenario you have to decode about 248 sequential Full HD H.264 frames before you can get previous image (so there will be major LAG). And you really cannot cache so many previous frames because they will eat all the memory very quickly.

So it will be either super slow in some cases or memory hog all the time.

Also not all access methods support random access all the time (so you really cannot seek), so it will cause frustatration in users when keys or GUI buttons don't work (this just a minor annoyance).

> Pierre.
> 
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