[Open-graphics] Amount of CPU required to decode video

[James Richard Tyrer]

Dieter wrote:
> Xbitlabs did some measurements on how much cpu it takes to
> play video.
> 
> http://xbitlabs.com/articles/video/display/video-playback.html
> 
> Of course they did this with binary drivers for virus-server.
> And they didn't hunt down high bitrate sources.  Or tell us
> what the bitrate of the sources is.  And they used a x2 "FX"
> (expensive) cpu.  Some of the tests would have failed using a
> more normal cpu, much less a low end one, or an older model.
> 
> They do provide some maximum bitrates:
> 
>   DVD mpeg2 max bitrate approx 10 Mbps
> 
>   mpeg2 HD up to 80Mbps
> 
>   mpeg4 - DivX HD capabilities are formally limited to 1280x720 resolution
> 	at 30fps and a bit-rate of 20Mbps.  [ seems odd ]
> 
>   MPEG-4 AVC/H.264 - up to 40Mbps  HD-DVD and Blu_Ray
> 
> H.264 takes 2-3 times as much cpu as mpeg2.  (for whatever bitrate
> sources they used)
> 
> A "rather low bit-rate" H.264 would nearly max out a single FX cpu.
> So a higher bit-rate H.264 would fail on a single cpu, even with a
> "premium" graphics card.  Forget using a normal cpu, much less a low
> end or older model.  With an "entry level" card, their "rather low
> bit-rate" H.264 needed 67.2% of the x2 FX cpu.  A high bit rate
> H.264 might well fail even with their x2 FX cpu.
> 
> Questions:
> 
> 	How much hw assist are these graphics cards providing?  I get the
> 	impression that ATI and Nvidia concentrate on gaming, perhaps we
> 	can beat them at video decoding?

If we offer an add on card with a media processor chip, then yes.

> 	How much cpu is it acceptable to require?  CPUs have other
> 	things to do besides decoding video, so using 100% of the cpu
> 	is not going to work.  Is it really acceptable to require a
> 	high end x2 FX cpu?

I don't know if that is the question.  1080p/30 does require a high end 
dual core CPU.

-- 
JRT