[Skimmertalk] CW skimmer audio output stutters under load

[bubnikv .]

>
> It seems to me though that the CW skimmer audio filter is sharper and rings
> significantly more than the filter of the Rocky SW.
>

> What CW filter width are you using?

Bob, the ringing is very subjective and maybe I was wrong. You are right,
when I set the bandwidths at both the CW skimmer and the Rocky the same,
they seem to sound similarly.

> Thanks for the tip to manually limit the number of decoders.  That does
indeed make the audio much less glitchy (but sill not perfect).

Try to elevate the CW skimmer process priority. Open Windows Task Manager,
go to the Tasks tab, select the CW skimmer, then open the context menu by
the right mouse button, then select Set Priority -> High. CW skimmer spawns
a decoder subprocess, so you will need to elevate the priority on both CW
skimmer processes you find in the list of the Task Manager. I believe
(again, this is subjective, I have no way to measure it), that it decreases
the clicks a bit.

I am a software engineer and this issue is of a professional interest to
me. I went through BIOS settings (those are very limited on my laptop), I
went through various diagnostics tools. I found out, that just pushing the
sound data through the USB cable costs around 9% of the CPU time (of a
single core) on this old laptop, which is quite high. But the reported
latencies of the USB driver were reasonable, around 1ms per deferred
interrupt service routine. I am afraid that's all I can do without having
access to the CW Skimmer source code, which I obviously do not have and I
would very much love to have :-)

73, Vojtech OK1IAK

On Sun, Aug 16, 2015 at 10:43 PM, Bob Wilson, N6TV <n6tv at arrl.net> wrote:

> On Sun, Aug 16, 2015 at 12:29 PM, bubnikv . <bubnikv at gmail.com> wrote:
>
>> On that 2007 laptop, if I set the maximum number of decoders to 50, I
>> elevate the process priority using the Task Manager to High and the CW
>> skimmer is the only application loading the computer significantly, then I
>> get no drop outs and the CW skimmer is usable as a receiver. That is,
>> after
>> I disabled the WiFi driver, which was introducing regular latency spikes.
>> With 50 decoders, the two core machine has one core loaded to 50% (CW
>> Skimmer is single threaded only, it will not load the other core).
>>
>
> When I play back a recording with CW Skimmer, and look at the Windows Task
> manager, I see both CPUs being loaded equally (PC has an Intel Core 2 Duo
> processor).
>
>
>> It seems to me though that the CW skimmer audio filter is sharper and
>> rings
>> significantly more than the filter of the Rocky SW.
>>
>
> What CW filter width are you using?  From the CW Skimmer help text:
>
> "CW Filter has a bandwidth continously adjustable between 20 and 700 Hz.
> The green rectangle on the frequency scale shows the boundaries of the
> filter passband.
>
> "To change the filter bandwidth, press the Ctrl-Up and Ctrl-Down arrow
> keys, or turn the mouse wheel, or drag the green rectangle with the mouse
> in the vertical direction."
>
>
> Thanks for the tip to manually limit the number of decoders.  That does
> indeed make the audio much less glitchy (but sill not perfect).
>
> 73,
> Bob, N6TV
>