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Posts: 9 | Thanked: 1 time | Joined on Jan 2009
#1
I've been playing around with the frequency scaling settings on my N810 and lately I've noticed that whenever I play media on the built in Media player, the CPU frequency will be fixed to 330 Mhz even if I'm using powersave (which supposedly fixes it to 168 Mhz), performance (400 Mhz) or any other governor.

Using mplayer this also happens also but it bumps the speed to 400 Mhz instead. I guess this is one reason why mplayer plays better video in the N810.

Anyway this is not an issue but just a mere curiosity. Anyone has a hint as to why this happens?

Note: You can set the frequency scaling governor by installing and using the advanced-power-manager status bar widget from the extra repositories.
 
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Posts: 3,391 | Thanked: 4,385 times | Joined on Oct 2005 @ Germany
#2
The CPU and DSP frequencies are related to each other. Unfortunately the highest CPU frequency yields a low DSP frequency. Since the media player uses the DSP for decoding media, the CPU is scaled down in order to the scale the DSP to max.

OTOH, mplayer doesn't use the DSP at all, so the CPU is scaled to max, because DSP freq doesn't matter.
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#3
Very enlightening post, thank you.
 
Posts: 2,152 | Thanked: 1,490 times | Joined on Jan 2006 @ Czech Republic
#4
Also if I understood it correctly it is not possible to change frequencies while audio is playing without skipping (audio is always played by dsp) so the result is that if audio is played the frequency is fixed.

If it is played by one of pcm dsp tasks it stays at 400 (op_0) and when it is played by mp3/aac/whatever codec dsp tasks the cpu stays at 330 (op_1) (=>dsp is at 220, not 133)

There is a hack that leaves dsp at 133 and cpu at 400 even for mp3/aac decoding and it looks like it works (i.e. dsp is powerful enough even at 133).

for details see table
http://mxr.maemo.org/diablo/source/k...n800-dvfs.c#49

I'm not sure if it must stay at 400 for pcm output but I guess so (because if more cpu power is needed and audio is played it would click and pop when raising frequency) - see also comment here - http://mxr.maemo.org/diablo/source/k...800-dvfs.c#140
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Last edited by fanoush; 2010-01-12 at 12:00.
 

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#5
geez... Thank You all for clearing this up for me.
Now I can see that browsing and listening to the music can be sub-optimal in terms of speed
Is there any chance to get recompiled kernel?
It's ridiculous that playing simple sound slows everything down so much
 
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#6
Also if I understood it correctly it is not possible to change frequencies while audio is playing without skipping (audio is always played by dsp) so the result is that if audio is played the frequency is fixed.
Pops and clicks as well as the skips
 
Posts: 2,152 | Thanked: 1,490 times | Joined on Jan 2006 @ Czech Republic
#7
Originally Posted by XTC View Post
Now I can see that browsing and listening to the music can be sub-optimal in terms of speed
Yes and Real audio is the worst.
Originally Posted by XTC View Post
Is there any chance to get recompiled kernel?
It is part of pptp enabled kernel here
http://fanoush.wz.cz/maemo/#pptp-diablo
It also has few other fixes. DSP/CPU speed is tunable via /sys/power/op_dsp. 0 is 400/133, 1 is 330/220.
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