[hpsdr] Audio distortion in PowerSDR

[Henry Vredegoor]

Hi All,

After doing more testing I found the following:

I cannot reproduce anymore the strange behavior regarding the process
priority being reset to the default setting in PowerSDR after changing
sample rates/buffer sizes in PowerSDR. 
It must have been some exceptional situation created by myself after
experimenting with different settings of PowerSDR and WinXp.

Listening test indeed proved I had distortion free audio with PowerSDR
running at 10% - 20% CPU, (average abt. 15%), Process Priority "LOW", at
48Ks/s / 2K buffer.
Even at the lowest settings, this was for me the first time I had distortion
free audio.

Further experimenting lead me to try different settings in "My Computer",
Properties/Advanced/Performance/Settings/Advanced
(I hope I translated this correctly from my Dutch WinXp to English WinXp
settings names....)

Changing:

"Processor usage" optimalisation from Programs to Background services
"Memory usage" optimalisation from Programs to Systemcache

enabled me with my hardware/software setup (after required reboot) to change
to 192 Ks/s and 2K buffer without distortion!

Independent of the setting of the Process Priority for PowerSDR, the CPU
load caused by PowerSDR is abt. 30% max.
Setting it to "Realtime" however causes it to be less frequently interrupted
by other programs (always highest in the list in Task Manager, sorted by
"CPU")

Be aware however that these changes also affect other programs, witch can
exhibit unwanted behavior after these changes.

Hope this is useful for others while waiting for the announced "major
update" of the software.

73,

Henry.






> -----Original Message-----
> From: Henry Vredegoor [mailto:henry_vredegoor at hotmail.com] 
> Sent: dinsdag 17 februari 2009 4:49
> To: 'Phil Harman'
> Cc: 'hpsdr at lists.hpsdr.org'
> Subject: RE: [hpsdr] Mercury 2.6
> 
> 
> Hi Phil, Bill, All,
> 
> I made two strange observations:
> I was testing at a sample rate of 192 Ks/s, buffer size 1024.
> A lot of distortion.
> After having set the buffer size to 2048 it was even more distorted.
> 
> 
> I set the process priority to the LOWEST setting "low" (!).
> 
> Guess what: the distortion was A LOT LESS than at higher 
> process priority settings!?
> 
> I also found that after changing the sample rate or buffer 
> size, the process priority changed back to the default "high" 
> setting?!
> Is this OK/meant to be?
> It also works this way when changing VAC sample rate settings.
> 
> I wonder if this is the case with others or just in my setup.
> 
> I am now working at the lowest sample rate of 48K / buffer 
> 2048 and at a process priority of "low". 
> Processor load is 6 - 12% on an AMD 2000+ / 512 KB, WinXP 
> Home, SP3 (!)
> It sure is a lot more quiet now but I have to do more listening tests.
> It seems that other processes loading the CPU are 
> interrupting PowerSDR more though (I guess because of lower 
> process priority)
> 
> Henry.