[maemo-developers] Frequencies scaling with OS2008

[From: Frantisek Dufka]

Klaus.K Pedersen (Nokia-M/Helsinki) wrote:
> So what you are seeing is that the "DSP task policy" is active even
> though there are no dynamic dsp task loaded?

No, not exactly.

First thing - I did not know there is a way to output audio without 
loading dynamic dsp tasks (named pcm and possibly also pcm2 and 3). I 
guess this is new feature in OS2008 and with the frequency scaling 
complictions it looks like this feature is a solution to many 
performance problems (like videos in flash player) and is generally useful.

Also it makes the pcm dsp tasks (i.e. tasks playing just uncompressed 
audio) obsolete and worse choice because of lowered arm clock when they 
start.

So what I see instead is that gstreamer framework probably uses those 
pcm dsp tasks (instead of the new way) so when you are playing music in 
Real audio format (like the BBC radio preinstalled in the firmware) the 
audio is decompressed on CPU but pcm2 task is started and frequency 
drops to 330. And so in fact when listening to internet radio you are 
penalized twice with real audio - frequency drops and audio is decoded 
on cpu so user experince with microb is degraded. It is slightly better 
with MP3 audio but still it is unexpected penalty which did not happen 
with N800/OS2007 and 770 too. On those systems playing mp3 on background 
came virtually for free.

Also that is why I asked why there are pcm dsp tasks at all in OS2008? 
Or if they are there for better mixing than the logic which reduces 
clock from 400/133 to 330/220 should be more clever and kick in only 
when it is really needed. The switch (and audio click) is there anyway 
if you are first playing music in something SDL based (ScummVM) and then 
start audio via gstreamer (internet radio).

Frantisek