REW Beta Release LineUnavailableException trying to run at 48 kHz

dlr · Oct 16, 2024

I ran a test using the motherboard onboard sound out to the 1010LT input. The calibration and stepped THD ran successfully. The distortion levels are seriously bad, this is a very old PC, but it works using the FlexASIO WDM-KS driver. When I tested FlexASIO with the Scarlett only, full I/O, it worked. But switching back to the Scarlet-1010LT started having an error that I still cannot eliminate, "Unable to start ASIO capture". Rebooting does not help. Yet WDM-KS driver still does. It seems that once something causes a problem with Wasapi in Windows, it doesn't recover. So I'm testing using the FlexASIO WDM-KS driver now. It never fails.

It looks like the problem using Scarlett-to-1010LT is related to USB. REW must time out on input due to delay in the output from the Scarlett on USB.

dlr · Oct 17, 2024

I shouldn't say time out in REW. It does run the calibration, but there's something wrong with the data transfer. Still seems related to USB or possibly the Scarlett itself.

dlr · Oct 20, 2024

FlexASIO using the WDM-KS driver is very stable. It reproduced the results I'd had early on, but they weren't correct as I thought. this is a loopback test from Scarlett to 1010LT at -25dBFS (the -20 was a mistake). They were too good.

48k FlexASIO WDM-KS THD vs Freq Scarlett -25dBFS to 1010LT.png

dlr · Oct 20, 2024

Calibration in REW will complete now with small tweaking in the FlexASIO_GUI app. The result is still far from linear, but I created a calibration file from that. Subsequent loopback measurements of Scarlett-to-1010LT look close to what I expected. I would like to ask John for his thoughts as to how/why it could be this way. When the calibrtion is run, the run-time graph rises quickly at first and appears to asymptote to the top.

Scarlett 2i2 to 1010LT FlexASIO WDM-KS Calibration.png

dlr · Oct 20, 2024

Subsequent loopback measurements using the cal file look reasonable.

48k FlexASIO WDM-KS THD vs Freq Scarlett -3dBFS to 1010LT Calibrated B-H4.png

48k FlexASIO WDM-KS THD vs Freq Scarlett -12dBFS to 1010LT Calibrated B-H4.png

48k FlexASIO WDM-KS THD vs Freq Scarlett -15dBFS to 1010LT Calibrated B-H4.png

48k FlexASIO WDM-KS THD vs Freq Scarlett -20dBFS to 1010LT Calibrated B-H4.png

48k FlexASIO WDM-KS THD vs Freq Scarlett -25dBFS to 1010LT Calibrated B-H4.png

dlr · Oct 20, 2024

Loopback tests of the 1010LT only show that the noise is rather high, but the harmonic distortion components are rather constant across the bandwidth. On the contrary Scarlett loopback tests show that above about -20dBFS the harmonic components increase rather dramatically, in particular the 2nd and 3rd.. This is borne out in the Scarlett-to-1010LT loopbacks above. I had thought that the Scarlett output distortion was more stable as output increased than it appears to be.

FlexASIO is evidently the best option if two audio processors are desirable to be used simultaneously as in my case. But there is still the question of the impact of the calibration. Subsequent loopback measurement run using the cal file does result in a perfectly flat 20-20kHz response.

Scarlett 2i2 to 1010LT FlexASIO WDM-KS Calibration using Cal file.png

phofman · Oct 21, 2024

There are no technical reasons why one method should produce different measurements to another method, provided both are bit perfect. ASIO through FlexASIO to Wasapi exclusive is just as bitperfect as java Wasapi exclusive itself - the same final destination, just complicated with the ASIO API callbacks in case of FlexASIO.

My 2 cents: your FlexAsio is not configured for Wasapi exclusive, it uses shared mode through the windows mixer which resamples for 1010LT running at some different samplerate, at which it is locked (would be visible in the config screens). That may also explain the uneven frequency response. As I said, the wasapi excl. debug logs would have most likely revealed what was going on as they list all formats/rates reported by the soundcard as supported. Neither the debug logs nor the config screens were posted here. FlexAsio just adds a redundant level of complexity.

John Mulcahy · Oct 21, 2024

dlr said:
I would like to ask John for his thoughts as to how/why it could be this way.

No idea, this is the first time I've seen a response like that from an interface.

REW Beta Release LineUnavailableException trying to run at 48 kHz

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