[osg-users] ImageStream and texture updates synch

Tanguy Fautre tanguyf at ARISTECHNOLOGIES.COM
Mon Mar 2 09:31:02 PST 2009


Hi Robert,

It's then probably a good idea to update the ffmpeg plugin to also use a pointer swap.

The current implementation of the ffmpeg plugin is not optimal. Internally there are already two buffers (a private and a public one), because of the colour conversion routines, synch issues, and also because of the vertical orientation (see void FFmpegDecoderVideo::swapBuffers()).

FFmpegDecoderVideo::publishFrame() and FFmpegDecoderVideo::swapBuffers() could be improved to feature a real double buffering (and remove the then-useless copy) so that FFmpegImageStream could implement a pointer swap.

I think I could tackle this and submit the modifications during this week.


Tanguy


-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Robert Osfield
Sent: Monday 02 March 2009 17:07
To: OpenSceneGraph Users
Subject: Spam: Re: [osg-users] ImageStream and texture updates synch

HI Tanguy,

You don't want a synchronization point in the image stream as it'd
cause the rendering thread to stall waiting for the movie reading
thread.  Rather than add such a sync operation, it's best to double
buffer the image data and then just do a pointer swap on the image to
tell it which buffer is current, this is what I implemented in the
xine-lib plugin.

Something else I have been wondering about is the possibility of
having two ImageStream that are managed so that they are one frame
apart, then in the graphics thread you'd have a geometry with two
textures applied, and a mixing of the two textures based on the time
for the rendering frame vs the time of each of the texture.  This way
one might be able to provide a smoother video experience.   I must
admit, I don't know how effective this would be on movies, but it
might be an interesting thing to try out further down the line.

Robert.



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