Display stability with scope function at higher sample rate

[lorrain]

I enconter a problem with the display stability in scope function with a sample rate greater than 48Khz with a slight pb at 96Khz and strong pb at 192Khz. The trigger seems do not work correctly.
The problem is identical with an input signal from the generator REW or an external hardware generator. Generator is not concerned.
The pb is identical with all kind of input signals (sine, square, low or high levels, low or high frequencies) and all trigger parameters.
At 192Khz, I notice also in addition some artefacts. Photo attached.
I enconter similar problems with other scope softwares. Perhaps we are at the limit of what a scope software can do with a sound card and standard laptop.

In particular, I notice a high CPU load with my laptop (basic laptop 3 years old) in high sample rate with scope function running :40% extra load CPU at 192khz and only 15% extra load at 48khz.
Graphic processor load is not depending sample rate (6% extra load with scope running at sample rate 48Khz or 192Khz). John, what is your opinion about this.
However, this scope function remains very interesting.
Thanks.
Eric

 

[John Mulcahy]

What artefacts are you referring to in the image?

 

[lorrain]

I did some investigations and I have better understanding of all my problems.
I notice 2 kind of problems which have the same cause.
I notice at high sample rate (96Khz and 192Khz) 2 abnormal behaviers:

• Artefact (see photos)
• Instability display (trigger no very efficient).

My configuration:
Channel 1 is connected to REW generator (sine) and channel 2 is connected to external generator (square).
Sample rate 192K
There is an artefact once every 3 to 4 seconds in this configuration.
The cause is the CPU load. I notice these problems when processor load is below 30% to 40%.
The 2 defaults seems totally linked.
It seems that REW scope function takes large cpu load with my laptop at high sample rate configuration.
Cpu load at 192Khz goes from 5% to 30% / 45% depending many parameters such as REW scope window size, …).

My laptop is:
LENOVO IdeaPad L340-17API
CPU = AMD Rysen 3 3200 = dual core 2,6Ghz
Soundcard connected with USB3

I am happy with conclusion. REW is not totally concerned.

this

 

[John Mulcahy]

Looks like a dropout in the data capture. If there are data dropouts the trigger will also be unstable. Are you using Java drivers or ASIO?

 

[lorrain]

I use ASIO drivers but I have the same result with java drivers.