[Skimmertalk] CW skimmer audio output stutters under load

Pete Smith N4ZR n4zr at contesting.com
Thu Aug 6 06:38:36 EDT 2015

Vojtech, I suggest you write directly to Alex VE3NEA about this.  To my 
knowledge, he is the only one who fully understands the internals of CW 

I'm wondering, though, whether your 2007 PCmay have USB 1.0 ports, 
instead of USB 2.0.  If so, that could impose some pretty severe 
limitations onthroughput. Can you try it with the laptop's internal 
sound components at 48 or 96 KHz, whichever it supports, and see whether 
you still have the glitches.

You don't mention what receiver you are using, but if it simply provides 
I/Q audio to the sound card, that should not be the source of the problem.

73, Pete N4ZR
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On 8/6/2015 5:47 AM, bubnikv . wrote:
> Hi gang.
> I am having issues with the CW skimmer audio output. I am running the CW
> skimmer on a 2007 top notch laptop with an external USB Sound Blaster X-Fi
> sound card. The laptop seems to be just adequate to run the CW skimmer on
> 40m at 96 ksamples per second. The skimmer decodes all right and I see no
> glitches on the waterfall. But when I enable the audio output, I hear quite
> a lot of glitches once the CW skimmer activates around a hundred of
> decoders. MME or WDM does not make a difference. I am using the drivers
> from Creative. I tried to lower the maximum amount of decoders in the CW
> skimmer preferences, but it does not seem to make a difference.
> I get similar audio glitches with the Rocky software on the same hardware
> once the computer CPU is loaded. When running the Rocky software on the
> foreground as the only application, the audio is perfect. This all
> indicates, that the length of the audio output buffer used by the CW
> Skimmer is too short for the accumulated latency of my aging laptop. I
> suppose Alex keeps the sound input / output buffers as short as possible to
> keep the latency low. But this does not work well with my aging laptop and
> the USB sound card.
> Is there a way around it? Is there a way to increase number of sound output
> buffers?
> Thanks and VY 73,
> Vojtech OK1IAK, AB2ZA
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