[FFmpeg-user] Issue Overlaying Video from x11grab and video4linux2

Ian Milligan ianmllgn at gmail.com
Tue Dec 3 01:26:47 CET 2013

When I capture video directly from x11grab at 30 fps it seems to work
correctly and the encoder reports getting about 30 fps. Here is what the
output looks like: http://pastie.org/8524085. However when I try to capture
simultaneously using video4linux2 and overlay the two streams, the encoder
reports getting only about 5 fps. Here is some sample output:
If I understand correctly, the overlay filter should use the timestamps
from the first input stream, so the fps should remain unchanged in the
overlayed video. I have noticed that using -r 30 on the x11grab input
creates a 30fps output stream, so perhaps this is a problem with the
timestamps being returned by x11grab. Any ideas?

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