[vlc-devel] Video Filter Input Buffering

Darrell Walisser darrell.walisser at gmail.com
Thu Feb 11 21:46:57 CET 2016

I am new to VLC development and working on a new "y4m pipe" video filter.
The idea is to read/write frames to a subprocess that does the actual
filtering, using YUV4MPEG2 to package the frames going back and forth.

I have something that mostly works and will perform well enough to be
useful, however there are a few issues remaining. The main problem is that
I can't achieve a buffer on the input, while also being able to supply
valid output, specifically the output date/pts on the returned pictures is
before  the input picture due to buffering in the subprocess.

Initially, it seemed possible to return a NULL picture for the first few
pictures, until some output pictures were available. This appears to "work"
in the sense that the output is displayed, however it comes late in terms
of the pts, the message from the video output is "Unsupported timestamp
modifcations". Even if I could somehow supply correct pts, I assume it
would be "late" and have to be dropped from the vout's perspective.

Maybe someone has an idea how to do this or what modifications to VLC would
be needed to pull this off? Besides my use case it might be a good feature
since filters could process several frames in parallel instead of being
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