[vorbis] Performance tests

[Hongli Lai]

On 2001.10.16 20:58:14 +0200 Rik Hemsley wrote:
> #if David Balazic
> 
> > Do not use top under linux either !
> 
> Note for future reference: If you want to test the CPU usage of
> decoding under Linux, simply use something like the following:
> 
> time ogg123 -d null file.ogg
> 
> Or for mpg123:
> 
> time mpg123 -t file.ogg
> 
> The 'user' value is a good guide to the amount of CPU needed, in
> seconds.
> 

That won't work. ogg123 will simply use 100% CPU because it will
decode things faster than realtime.

I just found out why people say Vorbis use 10% CPU.
Previously, I use GNOME with a CPU monitor applet.
When I play a Vorbis file, the applets says that about 50% of the
CPU power is in use.
I now use Gkrelmm in Linux, and it's CPU monitor has a much smaller
interval.
There are two display types for the CPU in Gkrelmm:
a graph-based display just like the GNOME CPU monitor applet, and
some kind of arrow that updates every 0.05 second or so.

When I play a Vorbis file, I see the arrow flickering somewhere around
5%, then after half a second it suddenly increse to 50%, then instantly
drops to 5% again.
After half a second, it increses to 50% again, then drops again, etc.
But the graph (which has an interval of 0.5 second) tells me that
the average CPU usage is 10%.
So perhaps all this is just caused by the CPU monitors with a too small
interval time.

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