Stuttering audio and then crash

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TwinStar
Posts: 3
Joined: Thu May 04, 2023 8:35 am

Stuttering audio and then crash

#1

Unread post by TwinStar »

Hi!

I recently came across this wonderful piece of software and have been playing around with it since then. The CUDa processing intrigues me a lot and I decided to see what bandwidth my computer is able to handle when using my LimeSDR USB transceiver. For comparison I deactivated the CUDA offloading and started with a 2 Mhz bandwidth just to check the CPU load. I gradually increased up to 20 Mhz when the audio started to stutter and the waterfall started to lag. Running a stock i7-3770K the CPU load was stable at around 40%.

I decided to switch on CUDA and the CPU load dropped to about 8-10% as my GTX 970 increased its load to about 4%. The audio stuttering and waterfall lag continued however. I increased the bandwidth to 30 Mhz and the symptoms got even worse. The CPU and GPU load were still negligable. Just for the fun of it I increased the bandwidth even further to 40 MHz and then the console crashed.

I'm running Windows 10 22H2 with 32 GB RAM and SDRConsole V3.3 Build 2848.

Was this a total newbie mistake to increase the bandwidth this far or what can cause this stuttering even though the CPU is far from maxed out? And why didn't the CUDA activation make any difference to the stuttering and waterfall lag?

Kind regards,

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KA1GJU
Posts: 264
Joined: Tue Aug 11, 2020 2:16 pm

Re: Stuttering audio and then crash

#2

Unread post by KA1GJU »

OK... I'll be the one with bad news...

Before we start throwing darts at the wall, lets start here:
https://www.sdr-radio.com/screenshot

Please use the "Full Editor" below while composing your next post and ATTACH the image. So we can see all the important stuff on the edges.
Only then will somebody be able to help.

73 Kriss KA1GJU
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

TwinStar
Posts: 3
Joined: Thu May 04, 2023 8:35 am

Re: Stuttering audio and then crash

#3

Unread post by TwinStar »

I don't know if I did everything correctly but here comes the screenshot. The lag isn't visible in the image however. After my first post I noticed that I wasn't using the latest version so I immediately downloaded build 2949 and tried again. This time I wasn't able to replicate the crash at 40 Mhz bandwidth but on the other hand the stuttering/lag starts at a somewhat lower bandwidth now.

Screenshot-2023-05-05-205319.jpeg

Max
Posts: 859
Joined: Thu Aug 13, 2020 9:47 am

Re: Stuttering audio and then crash

#4

Unread post by Max »

TwinStar wrote: Thu May 04, 2023 8:50 am Running a stock i7-3770K the CPU load was stable at around 40%.
That's an 11 year old proc makes me wonder..... are you 100% sure that you are using at least a USB3.0 port? If you are using USB 2 then it will not have the data rate to support what you are trying to do. That's my first major suspicion of where to look.

Also if you are using a USB 3 port, make sure it's not shared with other devices i.e. via hub shared with other USB 2 devices because they can drag the data rate down to their data rate so totally defeating the object. Make sure to use USB 3 only and dedicate that port only to the Lime.

Also, although they don't sound high, those loads are quite high for SDRC (proc at 10%+). Having said that I was using same age proc i7 and mobo until very recently and it was always smooth with GTX 1650 Super in Cuda mode) but I never had an SDR that anywhere approached that kind of bandwidth. I think you might possibly be stretching the capabilities a little at those sort of bandwidths even if it does not look like it?

But I would say first port of call is to check the USB situation.

Max

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KA1GJU
Posts: 264
Joined: Tue Aug 11, 2020 2:16 pm

Re: Stuttering audio and then crash

#5

Unread post by KA1GJU »

On the widest bandwidth SDR (2Mhz), my 5th generation i5 (i5-5200)@2.2GHz gives me a 40% CPU load on BC-FM. When I go to USB it drops to 23%. This is only at 2MHz bandwidth, where you are running 20MHz as far as my eyes can tell on the image. This laptop only has the Intel(R) HD Graphics 5500. But I have no issues with stuttering. Plus this is via my server, the rig is 400' away with two Ethernet switches inline!

Decoding FM seems to take a lot of processing, I learned that long ago due to the laptop fan kicking into overdrive when listening to BC-FM. How does it handle 20MHz of SSB?

73 Kriss KA1GJU
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

TwinStar
Posts: 3
Joined: Thu May 04, 2023 8:35 am

Re: Stuttering audio and then crash

#6

Unread post by TwinStar »

I've continued to look into this and I don't think that the processor is underpowered even though it's +10 years. There might however be USB-related as mentioned earlier, or related to the LimeSDR. The SDRC will handle 20 MHz BW from my HackRF over USB2.0 but not the same BW over USB3.0 from my LimeSDR. And then I've disconnected everything from the USB3-controller except for the SDR. As far as I can tell at least.

What I find peculiar is that the pitch of the audio is also increased when the BW is raised until the stuttering begins. When listening to a normal BC-FM radio station changing from 15 to 20 MHz on the LimeSDR the voices change to Smurf pitch. This is not the case when using the HackRF over USB 2.0. The modulation doesn't seem to affect the load however. 20 MHz SSB seems similar to BC-FM.

The performance gain from CUDA offloading is massive though. My one year old i5-10500T (6C/12T) with built-in graphics (another computer) struggles to achieve more than 15 MHz while this +10 year old computer with a GTX 970 doesn't break a sweat during the same circumstances. Apart from the stuttering of course.

15MHz without CUDA offloading (66% CPU load)
Screenshot-2023-05-06-071406.jpeg
20MHz with CUDA (11% CPU / 20% GPU load)
Screenshot-2023-05-06-071606.jpeg

Regards

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