[FFmpeg-user] scale input video before transcoding

Carl Eugen Hoyos cehoyos at ag.or.at
Mon Mar 12 19:22:55 CET 2012

jacob s <jacobhameiri <at> gmail.com> writes:

> -f dshow -i video='screen-capture-recorder':audio='Stereo 
> Mix (IDT High Definition' -vcodec  libx264 -preset ultrafast 
> -r 10 -async 1 -ab 32k -ar 22050 -f mpegts udp://

Complete, uncut console output missing.

> When using this command ffmpeg uses about 65% CPU 
> ( Pentium4 2.8 GHz ), and after a short while I am 
> seeing glitches in the viewing machine.

Note that the Pentium4 has known limitations 
(that may or may not be the reason for your problems).

> I thought of reducing CPU usage by scaling the input video 
> to 50% - 75%, but even after scaling to 50% CPU usage doesn't 
> change, I suspect this is

Command line and complete, uncut console output missing.

> because the scaling is performed after the transcoding process

It is not possible to scale after transcoding
(all scaling has to be done after decoding and before encoding).

Did you test encoding to a file instead of udp?
What speed / CPU usage do you see?

Carl Eugen

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