Stereo USB Input?

[KarlBystrak]

I just finished building my first BirdNet-Pi device from a pi4. Now I am looking for a USB sound card to do stereo input. I built my own microphones using 2 x AOM-5024L-HD-R Where I wired the two mics to a single TRS 1/4 audio plug. (One MIC's + Wires on TIP, one MIC's + wires on RING, and both MIC's - wires together on SLEEVE). I already tried the UGREEN External USB Sound Card Jack USB Adapter and it doesn't seem to be stereo? I am not really sure how to determine if the Pi is getting a stereo or mono signal. How would i check that? And does anyone have any suggestions on other adapters to try?

Thanks in advance!

[alexbelgium]

Hi, there is no benefit to a stereo system : the BirdNET model is trained with 16bits 48khz mono files. Therefore, the code converts any input sound to mono before testing it. The only impact of a stereo input is in the recording sounds.

[seanbirder]

I'm trying to decide on a version of the Clippy EM272M. Ideally, I'd have a microphone on the front of the house and the back of the house. Would it be better to have a stereo EM272M with long cords that can reach both side of the house, like this? https://micbooster.com/clippy-and-pluggy-microphones/270-2272-clippy-em272-custom-mono-microphone.html#/35-single_2_4_matched_capsules-2_matched/83-plug_type-straight/161-cable_length-10_m/202-microphone-em272m

Or, would it be better to have two separate mono mics? If two separate mics, would it be better to feed both of them into the same Raspberry Pi, or should I have two Raspberry Pis? Thank you for the input.

[alexbelgium]

Hi, watch out clippy em272 with aux cables is prone to interference. Long cables will exacerbate this.

The xlr version will be less susceptible to interference but will need a costly audio converter.

A solution that was taught to me by @lloydbayley : use a usb to ethernet converter (10euro the pair on amazon) then a ethernet cable, then plug the ugreen mini at the end of the ethernet to usb converter :) I did this and it actually worked but a ugreen converter. Not with all models though. The usb protocol especially with a shielded cable will prevent interferences. I did that with a 30m long cable! Worked great.

Second issue is to analyse the 2 signals. I don't think pulseaudio supports both. What I've done is therefore have small rpi3b near the mics that convert the signal to a rtsp (https://github.com/alexbelgium/hassio-addons/blob/master/birdnet-pi/DOCS.md#set-rtsp-server), then read the multiple rtsp feeds from the rpi.

[seanbirder]

Thanks for the interference tip. I will give that a shot!

I think I understand your 2-signal setup. Tell me if this is correct. You are using two separate mono mics. Then each of them have their own rpi3b. Then do you output the RTSP signal with an ethernet cable, or wireless via LAN? These two RTSP signals feed into the main rpi. Is this correct?

[alexbelgium]

Hi, here is a small schema for what I was thinking. Indeed each is a mono mic (either TRRS with a ugreen system, or XLR with a phantom-power enabled audio card). If you use a non-XLR microphone make sure that both your card and mic have the same format (TRS or TRRS)

The only issue is that it's not possible to mix pulseaudio & rtsp feeds ; it would be easier. If you have 2 it should be both RTSP.

A last alternative is that you run homeassistant with 2 version of the BirdNET-Pi addon ; and link each feed to a single BirdNET-Pi analyzer

[poundy]

I bought the same ugreen device. If you configure the device in birdnet with 2x channels, you'll get no detections or recordings and your log fills up with errors telling you the hardware doesn't have that many channels. you can use arecord to test that as well, using -c1 versus -c2 for stereo you'll see the error.

I too built up a dual AOM-5024 unit. Guess on v2 I will only use one !

[BlipRanger]

I think (and I could be wrong), that the UGreen device actually doesn't have 2 channels. I tested it extensively across a few computers with various drivers and it only ever revealed a single channel input despite being a TRS input.

[BlipRanger]

After having no success with the ugreen for stereo, I ended up using the RODE AI Micro and it just worked to provide stereo recordings / live stream. Costly, but working. I did have to plug the interface into my phone first to set it to stereo instead of combine, but otherwise smooth sailing.
@alexbelgium, in your experience, is this ugreen interface supposed to be 2 channel input?

[alexbelgium]

Hi, I never used that ugreen one but with trrs I ended up with the Rode Ai micro also which is great. Then I switched to an xlr mic but honestly I'm not sure there is a real difference beyond the theorical elements

[KarlBystrak]

I also tested this: https://a.co/d/8MziGjm and it did not do stereo. I have a Rode Ai Micro and I know it works but the cost is too high for this project. I was seeking a cheaper solution. My plan was to try this next: https://a.co/d/dwJ2ea1 but I stopped when it was mentioned there was no benefit to stereo input other than for the human listener.