[vlc-devel] [PATCH 2/6] vout: Allow vout modules to request extra filter pictures

[Julian Scheel]

Am 19.06.2014 13:24, schrieb Rémi Denis-Courmont:
> Le 2014-06-19 17:22, Julian Scheel a écrit :
>> Some video filters, especially hardware implementations with questionable
>> APIs, might require more than 3 pictures to send to the filter. As those
>> filters are most likely tight to a specific vout anyway allow the vout to
>> pre-request additional buffers for the filters, so that direct
>> rendering can
>> still be used.
>
> I don't understand why the vout module needs to request more buffers
> from itself. Or rather, why doing that requires core changes.

In fact the mmal based video_filter requires those extra buffers if the 
vout is in opaque mode. This is due to some oddities in the buffer 
handling behaviour of mmal when running in opaque mode.
The core needs to be aware of it because the video filter requests 
pictures out of the private_pool, which so far was hard-coded to 4 a 
size of 4 pictures. Hence a video filter was not allowed to request more 
than 4 pictures in direct rendering mode. Now with the existing 
behaviour of mmal we simply need more whenever the vout is in opaque mode.