K1LSB wrote:Scott,
I've read that post before.
1) The post is specifically about PowerSDR, not Thetis.
I had hoped you could make the leap between the two programs, but apparently not. The resampler is the same in both programs and performs the same functions for the same reasons, which are (quoted from the link above):
"Adaptive Variable Resampler:
This release of PowerSDR mRX (and in the equivalent Thetis release) introduces an optional Adaptive Variable Resampler option for VAC audio. The implementation is a true resampler and not just a data "smoother".
Since both the radio and the PC use different clocks to obtain their nominal 48KHz audio sampling rate, the rate in the radio will not exactly match the rate in the PC. This sample rate mismatch leads inevitably to audio buffer under- and over-runs that often result in audible glitches in the VAC audio streams, both transmit and receive. The resampler acts to transform audio data across the radio clock domain and the PC clock domain, thereby substantially eliminating these glitches. The resampler also works for those who are using the VAC IQ data output at all IQ sample rates, and spur levels will be extremely low even at 192KHz."The post speaks of "Resampler" checkbox in Setup > Audio > VAC1" but I see no such checkbox in Thetis.
There are many differences in the UI between PowerSDR and Thetis. In Thetis the resampler is enabled by default, hence there is no longer a checkbox. However you can force disable it by selecting the "Force" checkboxes in the diagnostic display.
2) It also speaks of a "diagnostic display" but I can't find that either.
This is the same in both PowerSDR and Thetis and is comprised of the area marked "VAC1 Monitor" in both programs.
3) It speaks of setting the "primary buffer size" and "VAC buffer size" but I can't find either of those defined or designated anywhere.
I'm sorry that there is no specific documentation for every feature of both programs. That is unlikely to change unless someone volunteers to write it. At any rate (ha, a pun!) the audio portion of the code in Thetis is quite a bit different than in PowerSDR and there no longer is a Primary Buffer to be set. There is, however, in both programs, a Buffer Size setting in Setup > Audio > VAC1. You can't miss it (or maybe you can?)
4) It also says that "the smallest possible ringbuffer on the receive side is 512, the smallest on the transmit side is 1024", but both default ringbuffer sizes on my screen (mine are labeled "In' and "Out" ringbuffers, not "Receive" and "Transmit") are 120, much smaller than either of the numbers noted in the post.
Yes, ignore all that, it is PowerSDR specific. In Thetis, as already mentioned, the audio portion of the code has changed substantially. There are a number of new controls for Buffer Latency, none of which having any direct relationship with the resampler. However, anecdotally the resampler does seem to work better with smaller numbers in all of these boxes, and the VAC buffer size as well. You will have to experiment. I like to set the buffer to the minimum, port audio to 0 (manual), and then start messing with the ringbuffer (again on manual). You need a way to monitor receive audio coming via VAC1 to know what works and what doesn't, it can be very hard to determine this merely by looking at the waterfall in WSJT-X or Fldigi (for example). I like to use Voicemeeter because I can route the audio to my PC speakers and listen to it for glitches and whatnot when doing these adjustments.