Arch Linux

awayand

Member

Registered: 2009-09-25

Posts: 398

ffmpeg screen recording with best quality not possible

I am experimenting with ffmpeg to record my screen for screencasting.

I am using the following options:

ffmpeg -f alsa -i hw:0 -f x11grab -s wxga -r 25 -i :0.0 -sameq /tmp/out.mpg

I found that even though I use "-sameq", the quality of the recorded video is still a little lower than my actual screen, which is particularly annoying since I have lots of small text on the screen and the pixelation makes it hard to read.

What do I need to do in order to have 1:1 quality recording of my screen?

Last edited by awayand (2011-11-02 17:02:25)

DrZaius

Member

Registered: 2008-01-02

Posts: 193

Re: ffmpeg screen recording with best quality not possible

The -sameq option should almost never be used. It does not mean "make the output the same quality as the input" as the old documentation used to imply. The docs have since been updated upstream.  This option can be used when the input and output use the same quantizer scale in the same range. Quantizer only has a loose correlation with quality.

Your input from x11grab is RGB, and your output is YUV. The conversion from RGB to YUV will most often create an output that does not look as good as the input even if you use a lossless encoder. You can use an output that supports RGB, but most players only support YUV.