[MEncoder-users] mencoder flags

[R.L. Horn]

On Sat, 22 Nov 2008, Mplayer user wrote:

> Sorry for newbie questions, but I want to capture and store video from 
> outdoor cam. The resolution is 720x578, there is no fast motion and motion is 
> rare at all. I'd like not to use too much storage space, but keep picture 
> details.
> For now, I'm using 
> "driver=v4l2:input=0:noaudio:width=720:height=578:fps=1:norm=SECAM -of avi 
> -ofps 1 -ovc lavc -lavcopts gray", but result is rather fat IMHO, and I'd 
> prefer more fps anyway. What coder and flags can you recommend me for this 
> case?

Play around with the bitrate or quantizer (quality) options for whichever 
coder you choose.  E.g., with the lavc mpeg4 coder, try fairly large 
values of vqscale (you might try vqscale=10 to start) or low values of 
vbitrate.  The default lavc coder is 800kbps mpeg4 which, at such a low 
framerate, effectively results in the lowest vqscale possible.

> Another question is how to store files: I'd like to capture cam nonstop. 
> For now I'm thinking of using " -frames 600 " and restart mencoder with 
> endless cycle. Is there any better way to solve this problem?

None that springs to mind.

> Is there any way to encode current cam output and display it to user? Is 
> there any way to do it with different fps and different resolution? I'd 
> prefer to combine encoding 720x578 at 3fps with displaying 640x480 at 15fps 
> (like "mplayer 
> driver=v4l2:input=0:noaudio:width=640:height=480:fps=15:norm=SECAM -vo 
> svga").

Once you're encoding to a file, you can do something like:

   tail -c +0 -f [AVIFILE] | mplayer [OPTIONS] -

which may or may not produce acceptable results.