Stereo Tool

Pretty sure I've changed something I shouldn't have.

Stereo Tool is feeding uMPX. I'm running ST in mono with RDS. uMPX (on a Pi) is receiving stereo with RDS.
I have verified that the stereo generator is not checked in FM Transmitter and the output signal does not show the stereo pilot or the L-R. (I can't seem to figure out how to upload a screen shot) uMPX's web gui clearly shows L+R, Pilot, L-R and RDS. I have verified that a tuner shows stereo and the RDS. This is a talk station, so there is no need for stereo.

In a crazy twist, I just turned off RDS and it stops streaming to uMPX totally. Turning on RDS or the Stereo encoder brings it back. It has complained about the FM Output sound card not supporting 192k, but it's disabled, so I'm not sure what that issue is. I'm only running FM Transmitter and uMPX. All other outputs are disabled.

FWIW - uMPX is currently running unlicensed. Waiting on the permanent code. Don't think it is part of the issue but wanted to mention it.


Any help is appreciated!
Trey

Hi Trey,

Unfortunately µMPX doesn't support a full-mono stream yet. We're working on that though. That you're seeing a pilot is probably a bug, that's not supposed to happen. Which version are you using?

_________________
Imaging producer & Stereo Tool audio processing consultant

That's why I thought I clicked something to cause this behavior. It was passing mono and rds correctly at first.

Stereo Tool v9.23 under Win10 with a Orban 1101 for input.
uMPX decoder is v1.4.4 on a Raspberry Pi using the HiFiBerry DAC+ Pro XLR sound card.

Just noticed that if I stop the uMPX encoder in ST, the pilot is still in the output. RDS goes away.

Is there any benefit to running higher bitrates?


Thanks!
Trey

Before I can say anything useful I'll have to test this myself, I'll get back to you about this.

It's not likely you're going to hear the effect of a higher bitrate, though if you have the bandwidth and the connection is stable enough (which becomes more important with higher bitrates) there's not really a downside either. I would recommend to wait for µMPX 2 though (will soon be released), as it's a lot more efficient and stable (codec-wise) at higher bitrates.

_________________
Imaging producer & Stereo Tool audio processing consultant

If you would like me to test uMPX2 on a Pi, send me an email. I just ordered the hardware on Amazon to build another decoder. It should arrive today.

In a slight twist of the use of uMPX, it would be useful if it could transport audio (not composite) using the error correction built into uMPX. Use it as a IP STL transport where the processor is still at the tower. (along the lines of the Z/Ip, Bridge-It, Barix, Bric-Link, etc) but using PC's or Pi's. Some of the boxes I mentioned are just getting crazy expensive for no real reason.


Trey

Hi,

We've tested sending mono with µMPX through Stereo Tool. It works, though there is a small bug in ST causing it to generate a pilot anyway. The trick is to set the 'Pilot volume' to 0%, even though Encode Stereo is disabled and the Pilot volume slider is greyed out. This will be fixed in the next version, but for now you can do this to make it work. The µMPX decoder then shows only L+R and RDS, but not L-R and pilot.

_________________
Imaging producer & Stereo Tool audio processing consultant