[MPlayer-users] recording at slow frame rate

Jeremy Sanders jss at ast.cam.ac.uk
Wed Jul 9 11:59:58 CEST 2008

Hi - I'm using a vga2usb input device to grab output to a projector to a
linux box, along with audio from a microphone. vga2usb has a v4l device
which supplies video at a variable frame rate depending on the screen
resolution, etc.

How can I can mencoder to record the video at a constant (slow) framerate so
that the video and audio are in sync and in real time? What happens is that
it records the incoming ~10 frame/s input frame-by-frame with a constant
playback frame rate. I'd like mencoder to drop incoming frames so that a
constant input and output framerate is achieved.

Currently I have this command line:

mencoder -ovc x264 -x264encopts bitrate=100 -oac lavc -lavcopts
acodec=ac3:abitrate=128 -vf scale=1024:768 -o out.avi -tv
driver=v4l:outfmt=bgr24:device=/dev/video0:adevice=/dev/dsp1:forceaudio -fps
2 tv://

This makes a 2 fps output file, but it uses each incoming frame, so
everything is slowed down. Eventually mencoder runs out of buffer space:

Pos:  45.0s     90f ( 0%)  2.02fps Trem:   0min   0mb  A-V:0.000 [98:127]
video buffer full - dropping frame

video buffer full - dropping frame

video buffer full - dropping frame

Has anyone any suggestions?



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