[vlc-devel] [PATCH 03/15] core: add viewpoint to change the yaw/pitch/roll view during playback

Rémi Denis-Courmont remi at remlab.net
Wed Nov 9 18:57:06 CET 2016

Le tiistaina 8. marraskuuta 2016, 11.22.49 EET Steve Lhomme a écrit :
> >> I believe that there is a reason why there are no getters in this file:
> >> they simply make no sense. By the time the function returns, the mutex
> >> is already unlocked, and the obtained value is already meaningless.
> > 
> > We need a way to get the current viewpoint to modify it later. Another
> > option would be to have no getter/setter and just the increments we
> > want compared to the previous call.
> One big drawback of that approach is that the "controller" would need
> to send the changes since its last increment, not based on the
> original reference point. And incrementing/decrementing floating point
> values many times will lead to rounding issues. When you come back at
> your original physical point you may not point exactly in the same
> place. And it will get worse the longer you use this system.

No, this is a red herring. There is no such drawback.

I mean, sure, if you remove the getter, you cannot do atomic read-modify-
write, because you no longer have a "read". But this patch does not support 
atomic read-modify-write anyway.

Arbitrating changes to the video output configuration is the responsibility of 
upper layers (also audio output). I don´t see why viewpoint would grant an 
exception here.

Rémi Denis-Courmont

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