[MEncoder-users] expert help wanted for realvideo transcoding!

[Reimar Döffinger]

On Fri, Apr 03, 2009 at 02:34:49PM -0700, Karlis wrote:
> Can mencoder autodetect audio/video bitrates and framerates? Or do I  
> have to inspect each file with ffmpeg, determine the audio/video  
> bitrates and framerates, and specify that in the mencoder options? 

-identify should print mostly the same info as FFmpeg.
Though there obviously is the question why you would want to do it,
e.g. if you don't want to lose quality vqscale=2 instead of vbitrate
is far simpler and more reliable, particularly single-pass bitrate-based
encoding usually does not work well.

> I'm currently already doing something like this for the video codec:  
> mencoder doesn't seem to recognize the difference between rv20 and rv30,  
> so I check the file for rv20 with ffmpeg, and add the "-vc rv20" if I  
> detect rv20.  Do I have to do this for every parameter?

Huh? I have _never_ seen anyone need -vc rv20 to decode RealVideo.
Also with that one you force MPlayer to use the binary decoders from Real
which seems like a bad idea to use on such "cloud" services.

> mencoder %s -ni -vc rv20 -o %s -oac mp3lame -lameopts abr:br=56 -s rate  
> 22050 -ovc lavc -lavcopts  
> vcodec=flv:vbitrate=300:mbd=2:mv0:trell:v4mv:cbp:last_pred=3 -fps 15  
> -ofps 15 -mc 1 -of lavf

-fps 15 overrides the input frame rate to 15 fps, if that is not absolutely
correct it's no surprise you get sync issues.