[mythtv-users] MPEG4 Bitrate effect on processor load..

[Bruce Markey]

Kevin J. Slater wrote:
> I thought I saw this somewhere in the past, but maybe I'm just demented. What
> effect does increasing the bitrate have on the processor when doing MPEG4
> encoding. For example, say you have a low end machine doing both front and
> backend duties and you're trying to optimize overnight recordings. Assuming 320
> x 480 capture resolution as a constant, does higher bitrate equate to less
> processor work and therefore less likely to have lost frames but at the same
> time give you larger files? (i.e. less compression == less work?)

This has come up in the past and it is a fair question.
A higher bitrate for MPEG4 uses more CPU time to calculate
all the bits it needs to write out. However, increasing
the bitrate by 20% doesn't increase the CPU usage nearly 
as much as increasing the resolution by 20%. If you're CPU
bound, lower res with a higher bitrate with give you more
bang for the buck.

--  bjm