[vlc-devel] Video filter - picture_t versus subpicture_t

Juha Jeronen juha.jeronen at jyu.fi
Fri Feb 3 22:35:09 CET 2012

On 02/03/2012 09:03 PM, Peter Tap wrote:
> Hello,
> Having written a stream filter, I am somewhat experienced with VLC
> development. For my current requirements, I need to extend VLC so that
> small image(s) can be displayed at specific times while a movie is
> being played. The closest to what I am doing is probably "dynamic
> logos." In my case, the picture has to be generated dynamically as it
> contains current time information.
> To understand how to write this, I have been looking at the code for
> dynamic logos. However, the code is a bit complex to grasp. I would
> appreciate your help in understanding the basic concepts:
> 1. What is the difference between picture_t and subpicture_t? I was
> thinking a subpicture is only a small part of the picture and that is
> what I need to blend with the actual picture. However, it appears
> filter_Blend requires picture_t and not subpicture_t as parameter.

subpicture_t is used for subtitles, I believe.

As for 2. and 3., I'm not qualified to comment. Deinterlace only does
50% blending using its own code (inline asm optimized), and isn't
perhaps the simplest video filter :)

If someone knows better/has more specific info, I could update the
hacker's guide for video filters on the wiki :)


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