[FFmpeg-devel] small patchset for ffmpeg -vf cleanup

[Clément Bœsch]

I'm working on the -af option for ffmpeg (in order to later use the audio
filtergraph for -map_channel), based on the original patch by Stefano. Since
the patch is pretty old, I had a look to the current video frame polling code.
While trying to understand that code, a few simplifications and clarifications
appear to me, so here is a small patchset.