Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Thu Sep 08, 2022 1:32 pm

W6LVP wrote:My Mini PC is small and probably too lacking in clock stability for this task.
That's extremely unlikely. Even the lowest spec. PC will have more than sufficient clock stability.

However, the little box uses just 5% of its CPU to run Thetis, VARA, and VarAC.
More power than you need. You should have no problem with that machine.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby W6LVP » Thu Sep 08, 2022 2:49 pm

Is there a way to determine when the resamplers are stable and ready to use? I have seen situations with no over or underruns but with the audio output frequency still slewing. Would no over/underruns AND the ring buffers fairly stable near the middle be a good indicator? Does reducing the ring buffer size shorten the phugoid?

Larry
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby W6LVP » Thu Sep 08, 2022 4:00 pm

More progress.

If you tick the Auto box above the two graphs in the lower right corner, there is a good depiction of the state of the resampler servo. The amplitude of the variation is a direct indication of the Doppler shift caused by the pointer moving. I haven't yet determined the maximum acceptable peak-to-peak swing but the data is there.

My problem is patience. Most any change to the VAC settings will disturb the resampler servo. Initial Thetis launch will also restart the process. It seems that ticking the two Old VAR boxes on the Advanced page might accelerate the post launch stabilization process by using the values from the last session.

With my less than optimized configuration, the time to reach acceptable servo stability is several minutes. Seems to me that if you create a reasonable VAC resampler configuration and give it time to stabilize, it works fine. If you launch Thetis and give the servo time to stabilize, all is good.

I will give this a try and see how it goes.

Larry
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Thu Sep 08, 2022 5:12 pm

W6LVP wrote:More progress.

If you tick the Auto box above the two graphs in the lower right corner, there is a good depiction of the state of the resampler servo.
As discussed throughout this entire topic. Have your read the topic from the beginning?

You don't have to use the Auto box, you can manually adjust the scale with the value in the box to the right of it. Adjust either/both settings to taste to see usable information in the graphical display.

The amplitude of the variation is a direct indication of the Doppler shift caused by the pointer moving.
This is not "Doppler", this is the "Var Ratio" or, more properly, the ratio between the two, different 48KHz clocks in the two separate clock domains (PC and ANAN hardware). The graph merely shows the fractional part as a difference from perfect, where perfect is a ratio of 1.0 exactly.

For example, if you see a Var Ratio of 1.000010, the graph will show +0.000010, and if one clock is exactly 48KHz the other clock will be at 48.0005KHz (0.5Hz difference).

My problem is patience. Most any change to the VAC settings will disturb the resampler servo.
It's worth noting at this point it's not a "servo", it's a feedback loop with a moving average.

Initial Thetis launch will also restart the process. It seems that ticking the two Old VAR boxes on the Advanced page might accelerate the post launch stabilization process by using the values from the last session.
Yes, any change to VAC settings will completely restart the process.

With my less than optimized configuration, the time to reach acceptable servo stability is several minutes. Seems to me that if you create a reasonable VAC resampler configuration and give it time to stabilize, it works fine. If you launch Thetis and give the servo time to stabilize, all is good.
Again, this is well discussed throughout this entire topic. Have you read from the beginning?

Ultimately, for me personally, I settled on only making two changes in the Advanced tab:

Feedback Gain: 0.0000001 (1E-07)
FF Alpha: 0.001

I found these to be a good compromise between stability of the Var Ratio (as you note, the absolute value of this number is not important as long as it is correct, it is any variation in this number that causes problems) and the settling time of the resampler feedback loop.

The following workflow is recommended:

1. Without changing default settings on the Advanced tab, find the buffer/ringbuffer/portaudio settings that keep under and overflow counters at zero, or at least close to zero (a few counts per hour is acceptable).

2. After achieving stable under/overflow performance only then attempt adjustments on the Advanced tab. Such adjustments will not strongly affect under/overflow performance but will act to stabilize variations in Var Ratio. If you have read this topic in its entirety you will know that the key adjustments are Feedback Gain and FF Alpha.

As discussed in my posts in this topic, I have the capability to lock my ASIO sound interface to an external GPSDO. With both the ANAN hardware and sound interface both locked to their own GPSDO, that is a best case situation. As you can see from my posts, the difference in performance between this best case situation and a properly adjusted resampler, while measurable, is functionally nil from any practical perspective:

viewtopic.php?f=13&t=3901&start=90#p16667
viewtopic.php?f=13&t=3901&start=120#p16729

Any frequency variations due to a wandering Var Ratio will be <<0.01Hz assuming proper resampler settings. This is far, far less than ionospheric induced Doppler, and therefore should be unnoticeable.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby K1LSB » Thu Sep 08, 2022 9:54 pm

Scott,

To say you have an uncommon handle on the intricacies of Thetis would be an understatement, lol!

Thank you very much for your tireless support of this community, sir. For my own part, I must say that ownership of my Apache Labs radio is much more rewarding thanks in very large part to your contributions to this forum, sir. It is difficult to find words to express my gratitude!

My apologies for hijacking this thread, I just felt the need to make that statement.

Mark
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Thu Sep 08, 2022 10:05 pm

:)

Thank you, Mark.

The resampler just happens to be one of my favorite subjects. There is plenty I don't know about our radios (like CW stuff). But thanks to the wonderful community we have formed here there is almost always someone who has the answer, and every such contribution is undoubtedly appreciated by all. The knowledgebase that has been accumulated here is extremely valuable, most of the time I just play librarian :D
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby rbduck » Sun Sep 18, 2022 2:04 pm

I'm glad this thread came back alive as it did. I have been experimenting with this for a long time. I've tried adjusting numerous settings. I started with one of the setup versions in a previous reply that seemed stable. With this the best I was able to see was zero's on the PortAudio in and out and 60 hz on the RingBuffer in and out. I was about to switch back over to my U-PHORIA UMC202HD Behringer sound card an see how that would pan out.I then ran across this thread again. I made the changes to Feedback Gain: 0.0000001 (1E-07) and FF Alpha: 0.001. I now see no Overflows or Underflows TO or FROM VAC1. This after it sits for a few minutes and stabilizes. I have ran for 48 hours with ZERO Overflows or Underflows and probably would have been good after that if I had not shut my PC down.

Now, this has worked great for receive. Transmitting is another story. I can also transmit and get NO Underflows or Overflows. People that hear me tell another story. They report that I sound like I am getting RF back into the shack. I know that is not the issue. To resolve this I have to put RingBuffer in AUTO mode. I then get very clear audio on transmit. This is with Pure Signal enabled. I'm wondering if I am the only person observing this behavior'?

Than you Mark, Scott and any others that have been diligently chasing these adjustments. I still intend to make the move back to the Behringer
sound card in a few days. I'm curious to see if I can change this transmit behavior. Again, my thanks.
73
Ruben
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w3ub » Sun Sep 18, 2022 2:14 pm

No, you are not alone. I have had the same TX reports (that I can also hear in the monitor). The problem is the issue is intermittent and there is no indication in the over/under flow counters.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Sun Sep 18, 2022 2:38 pm

Raise the size of the main VAC buffer. Also, if possible (it should be with the Behringer), make certain that the sound interface buffer size matches the main VAC buffer size.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby dondb1 » Mon Sep 19, 2022 5:11 pm

I also had the same issue of RF on transmit with the UMC 2020 HD and the Focusrite Solo, I tried both thinking the Behringer was bad. The problem would come and go. I ended up shutting the VAC off and going right from the front of the radio for both transmit and receive. With the Help from Chas ( K2BU) I installed a Ebtech Hum Eliminator to run my JBL speakers through with no RF. Scott...I'm not to far from you and you are welcome anytime to check out the set up. I still have the two interfaces and hope to use one again as I like listening to music off the internet through the JBL's.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w3ub » Mon Sep 19, 2022 5:32 pm

My issue was definitely not RFI, but issues with VAC that do not show up on the statistics. I like VAC for many reasons, including using a voice keyer.

Doug
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby rbduck » Mon Sep 19, 2022 5:57 pm

I read all and understand. I have been running a Sound Blaster AE-9 for awhile now. If I remember correctly, I was having identical issues with the Behringer I think. That was 2 years and one Covid ago so my memory may be questionable. I do love the experimentation.

I do know for a fact, these Apache 7000DLE's loud and crispy clean audio when tuned correctly. I have followed Bob's (A1AEX) step by step
instructions for getting the best audio using the the CFC audio tools in Thetis. http://www.w1aex.com/anan/profiles/tx_profiles.html I can only hope I have it correct. I have recorded myself from other Web SDR's receivers on the internet. I have a difficult time determining the quality because I don't get good enough reception from the Web SDR's.
I have tried different bands an different sites. I can mainly go by signals reports from others. They have been very good. I will accept that.

It's also a fact that I can just about tell you when someone is on an Anan when I hear it. I bet most of you also have that ability.

Anyway , got sidetracked! Thanks all!
73
Ruben
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Mon Sep 19, 2022 7:40 pm

dondb1 wrote:I also had the same issue of RF on transmit with the UMC 2020 HD and the Focusrite Solo, I tried both thinking the Behringer was bad. The problem would come and go. I ended up shutting the VAC off and going right from the front of the radio for both transmit and receive. With the Help from Chas ( K2BU) I installed a Ebtech Hum Eliminator to run my JBL speakers through with no RF. Scott...I'm not to far from you and you are welcome anytime to check out the set up. I still have the two interfaces and hope to use one again as I like listening to music off the internet through the JBL's.
Start a new topic about your RFI problem in either the Virtual Audio or Audio Hardware sub-forums and let's explore your difficulties further.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby rbduck » Tue Sep 20, 2022 7:16 pm

NB4R wrote:I'm glad this thread came back alive as it did. I have been experimenting with this for a long time. I've tried adjusting numerous settings. I started with one of the setup versions in a previous reply that seemed stable. With this the best I was able to see was zero's on the PortAudio in and out and 60 hz on the RingBuffer in and out. I was about to switch back over to my U-PHORIA UMC202HD Behringer sound card an see how that would pan out. I then ran across this thread again. I made the changes to Feedback Gain: 0.0000001 (1E-07) and FF Alpha: 0.001. I now see no Overflows or Underflows TO or FROM VAC1. This after it sits for a few minutes and stabilizes. I have ran for 48 hours with ZERO Overflows or Underflows and probably would have been good after that if I had not shut my PC down.

Now, this has worked great for receive. Transmitting is another story. I can also transmit and get NO Underflows or Overflows. People that hear me tell another story. They report that I sound like I am getting RF back into the shack. I know that is not the issue. To resolve this I have to put RingBuffer in AUTO mode. I then get very clear audio on transmit. This is with Pure Signal enabled. I'm wondering if I am the only person observing this behavior'?

Than you Mark, Scott and any others that have been diligently chasing these adjustments. I still intend to make the move back to the Behringer
sound card in a few days. I'm curious to see if I can change this transmit behavior. Again, my thanks.


It's been a week since I noticed this tread coming back to life.

After everything I previously said I have now spent a week testing the latest settings I spotted. After week I have to say the results were very positive. My settings are Buffer Size 2048, Sample Rate = 48000, Buffer Latency(Ring Buffer) = both Zero's and PortAudio = both Zero's. I I have a screen capture of the Setup>Audio window. I think the results posted are great! The only variables I changed were these located on the Setup>Audio>Advanced tab. Feedback Gain: 0.0000001 (1E-07) and FF Alpha: 0.001 Both results of Overflows and Underflows are excellent
This is only 24 hours of receiving and making contacts with Thetis. No restart or resets of Thetis. Let the results speak for itself. Well, I may stay with the original sound card (Sound Blaster AE-9) for a while longer.

SetupAdvanced.png
SetupAdvanced.png (36 KiB) Viewed 430 times
Setup.png
Setup.png (48.84 KiB) Viewed 430 times
73
Ruben
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Tue Sep 20, 2022 7:59 pm

That looks great. You'd be better off upping your TX gain in the audio card instead of VAC, though.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby K1LSB » Tue Sep 20, 2022 8:26 pm

Ruben,

Here's my settings and an explanation of why I'm running them:

My VAC buffer size is 64 (much lower than anyone else's I've seen posted), my RingBuffer is 5/5 and PortAudio is 0/0.

I learned early on that if I had buffer size set to 2048 (or even 1024) I could easily get away with running RingBuffers of 0/0, but I was looking for minimum latency so I kept reducing the VAC buffer size to 512, then 256, then 128, and finally all the way to 64. At some point (don't remember where anymore) I did see that I needed to start increasing RingBuffers to something greater than 0/0 to avoid my transmit audio from getting "robotic" sounding. I determined empirically that a RingBuffer setting of 5/5 settled down within a few seconds and was 100% reliable for RX and TX audio so that's the values I locked in to (again, that is with a VAC buffer size of 64).

I'm running a MOTU M4 interface with its buffers also set to 64. I'm also using Voicemeeter and have been informed that VM isn't designed to (and shouldn't be expected to) function reliably at all with a buffer size of 64, but it certainly does in my particular case so that's what I'm using!

I guess what I'm saying is if you decided to try a smaller VAC buffer size just to see if your TX audio was still stable, then keep reducing the buffer size until a "breakup" problem first appears, then stay at that buffer size and start increasing your RingBuffer size until the audio re-stabilized, you should then be operating at the minimum latency that your system can reliably support.

Scott, please do correct me if my latency logic is incorrect!

Thanks,

Mark

Audio VAC1.jpg
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Audio Advanced.jpg
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Tue Sep 20, 2022 10:12 pm

Everything is relative. Main VAC buffer latency equals size x 1/48000 (in seconds), or size/48 (in milliseconds).

So a buffer of size 64 = 1.3ms, of size 2048 = 42.7ms. Meanwhile the ringbuffer is adding it's own contribution. Shoot for the minimum combination.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby rbduck » Wed Sep 21, 2022 12:49 pm

rbduck wrote:
NB4R wrote:I'm glad this thread came back alive as it did. I have been experimenting with this for a long time. I've tried adjusting numerous settings. I started with one of the setup versions in a previous reply that seemed stable. With this the best I was able to see was zero's on the PortAudio in and out and 60 hz on the RingBuffer in and out. I was about to switch back over to my U-PHORIA UMC202HD Behringer sound card an see how that would pan out. I then ran across this thread again. I made the changes to Feedback Gain: 0.0000001 (1E-07) and FF Alpha: 0.001. I now see no Overflows or Underflows TO or FROM VAC1. This after it sits for a few minutes and stabilizes. I have ran for 48 hours with ZERO Overflows or Underflows and probably would have been good after that if I had not shut my PC down.

Now, this has worked great for receive. Transmitting is another story. I can also transmit and get NO Underflows or Overflows. People that hear me tell another story. They report that I sound like I am getting RF back into the shack. I know that is not the issue. To resolve this I have to put RingBuffer in AUTO mode. I then get very clear audio on transmit. This is with Pure Signal enabled. I'm wondering if I am the only person observing this behavior'?

Than you Mark, Scott and any others that have been diligently chasing these adjustments. I still intend to make the move back to the Behringer
sound card in a few days. I'm curious to see if I can change this transmit behavior. Again, my thanks.


It's been a week since I noticed this tread coming back to life.

After everything I previously said I have now spent a week testing the latest settings I spotted. After week I have to say the results were very positive. My settings are Buffer Size 2048, Sample Rate = 48000, Buffer Latency(Ring Buffer) = both Zero's and PortAudio = both Zero's. I I have a screen capture of the Setup>Audio window. I think the results posted are great! The only variables I changed were these located on the Setup>Audio>Advanced tab. Feedback Gain: 0.0000001 (1E-07) and FF Alpha: 0.001 Both results of Overflows and Underflows are excellent
This is only 24 hours of receiving and making contacts with Thetis. No restart or resets of Thetis. Let the results speak for itself. Well, I may stay with the original sound card (Sound Blaster AE-9) for a while longer.

Setup.pngSetupAdvanced.png


Hi Mark,

Like you, I have been chasing the latency bug since I have owned my Anan. It seemed like I have tried every combination of variables possible. In my case, no matter what combination I used I still came out with the same amount of latency. No matter what I tried I was only able to take my RingBuffer down to 60ms in and out. Anything lower caused uncontrollable Underflows and Overflows. The issue was that the only way I could get clear audio during transmit was to set both he RingBuffer and Port Audio to automatic. This made any latency reduction effort I have tried nil.

Then, I came across the Feedback Gain and FF Alpha settings I had not tried. I put that new set of numbers in and made both RingBuffer settings zero. I sit back and waited. I watched the Underflow/Overflow sort of dribble at first. Then after about 5 minutes they stopped accumulating. I waited a few hours and nothing had changed. At this point I tried the transmission side of the equation. I pushed the button and yelled "CQ".
he person responding gave me a good audio report. I thought WOW, Progress at last. That TX Gain of 15 is not what I normally run with. That is normally set to zero. I was just seeing how far I could push it and had not reset it to zero yet.

I wish I had more in depth knowledge into the settings on the advanced tab. In my experimentation with those I have only made things worse.
73
Ruben
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby Tony EI7BMB » Wed Sep 21, 2022 2:12 pm

Mark thanks for the screenshots. Using a Motu myself so this is very helpful
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby K1LSB » Wed Sep 21, 2022 2:38 pm

Ruben and Tony,

I don't understand any of the settings in the Advanced tab myself, I simply arrived at the values I did after much trial and error. I still have no idea of how the interdependencies of those settings behave or whether any of the values shown are actually optimal.

Also, the specific buffer size, RingBuffer settings and Advanced tab settings in my screenshots may not work reliably on your systems, given that my computer almost certainly isn't identical to either of yours. With that said, my machine is a rather ancient i7-6700K so your computer may in fact work just fine with the same settings as mine (and possibly with an even lower RingBuffer setting than mine).

It does at least appear that my approach to obtaining the minimum latency (i.e., finding the lowest reliable audio buffer size then slowly increasing the RingBuffer from 0/0 until underflow/overflow becomes stable) is a valid one.

Mark
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby w-u-2-o » Wed Sep 21, 2022 8:50 pm

K1LSB wrote:Ruben and Tony,

I don't understand any of the settings in the Advanced tab myself, I simply arrived at the values I did after much trial and error. I still have no idea of how the interdependencies of those settings behave or whether any of the values shown are actually optimal.
Did you read the explanatory material that pops up when you hover your mouse over the blue circles with the "i"?

Did you read the entire topic? If so, you'll see that Feedback Gain and FF Alpha can make big differences, and that changing the value of the other advanced parameters have little effect on performance. Making both Feedback Gain and FF Alpha values smaller results in a more accurate, more stable, and more highly smoothed (filtered) result for Var Ratio. This comes at the expense of settling time.
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby K1LSB » Wed Sep 21, 2022 9:39 pm

Thanks Scott, I don't think I ever read the Info popups but I did see (and only skimmed over) your earlier post regarding Feedback Gain and FF Alpha and had made myself a mental note to delve into your explanation more but TBH never got around to that, lol. But I did want to make it clear to Ruben and Tony that I'm clueless about that stuff at this current time, especially after having gone and posted the snapshot of the values I'm using.

Mark
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby rbduck » Thu Sep 22, 2022 2:21 pm

w-u-2-o wrote:
K1LSB wrote:Ruben and Tony,

I don't understand any of the settings in the Advanced tab myself, I simply arrived at the values I did after much trial and error. I still have no idea of how the interdependencies of those settings behave or whether any of the values shown are actually optimal.
Did you read the explanatory material that pops up when you hover your mouse over the blue circles with the "i"?

Did you read the entire topic? If so, you'll see that Feedback Gain and FF Alpha can make big differences, and that changing the value of the other advanced parameters have little effect on performance. Making both Feedback Gain and FF Alpha values smaller results in a more accurate, more stable, and more highly smoothed (filtered) result for Var Ratio. This comes at the expense of settling time.


Scott,
I guess you got me there. I say I try and read everything I can on this stuff and miss the most obvious of all. I will take note and be more observant in the future.

Mark,
I think you are the only person that I have heard on the bands. (that posts here) Your audio is absolutely fabulous.

Thanks for all the help guys!
73
Ruben
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby K1LSB » Thu Sep 22, 2022 5:03 pm

Ruben,

I'm pretty sure Scott's post was directed at me (and rightly so).

Mark
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby rbduck » Fri Sep 23, 2022 1:18 pm

K1LSB wrote:Ruben,

I'm pretty sure Scott's post was directed at me (and rightly so).

Mark


Thanks Mark,

I don't have a habit of reading that material either, which I should. And, sometimes the obvious just blows right past me.
73
Ruben
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Re: Thetis 2.8.11-21+++ VAC advanced controls: results and discussion

Postby K1LSB » Fri Sep 23, 2022 2:42 pm

Ruben,

And thank you very much for the audio report! :)

Mark

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