Birdfeeder

I wanted a way to get audio to BirdNET-Go (https://github.com/tphakala/birdnet-go) from low-budget devices spread across my property. This script turns a Pi into an appliance for exactly that purpose. I found that the actual capture and stream function leaves plenty of headroom even on a Zero 2W, so since BirdNET-Go can really only tell me if the RTSP stream is up or down, I implemented a simple busybox function to publish a "health" overview page on port 8080. Eventually, I plan to migrate away from the static page generation and publish to MQTT or otherwise integrate into Home Assistant for monitoring the node(s).

My setup:

1. Raspberry Pi Zero 2W
2. Micro-to-A USB adapter.
3. $1 USB sound card
4. $3 omnidirectional lav microphone.
5. Standard Pi power supply.
6. 3D printed case.
7. MediaMTX running on a separate server alongside BirdNET-Go in Docker on OpenMediaVault.

Functionality

• Captures audio from a USB sound card, encodes in AAC and publishes to an RTSP destination with FFMPEG.
• Optional: applies gain to audio before encoding.
• Optional: generates a static html system health page served on port 8080.

SETUP BASICS FOR PI ZERO W

1. Put birdfeeder-audio.service in /etc/systemd/system/
2. Put birdfeeder-audio.service in /usr/local/bin/

AUDIO CONFIGURATION OPTIONS

1. DEVICE: USB mic / sound card hardware ID (find via via arecord -l, mine tends to be 0,0)
2. RATE: Audio capture frequency (set to 48khz as that's my sound card's native)
3. BITRATE: Streaming bitrate, 128k seems to work just fine but this can be dropped down as needed, or increased with higher quality audio input.
4. URL: RTSP publishing path
5. THREAD_QUEUE_SIZE: Prevents loss of audio from spotty connections, good results at 4096.
6. GAIN_DB: Birdnet will normalize levels in clips, but live audio was low. I constantly used gain in the UI. Applying 15db gain worked for me.
7. LIMITER_LEVEL: This is just to prevent clipping, but realistically if this is utilized a lot, gain is too high.

HEALTH CONFIGURATION OPTIONS

1. STATUS_ENABLE: 1 turns on this functionality, 0 disables it.
2. STATUS_DIR: This is where we're writing the health information to periodically.
3. STATUS_INTERVAL: This is how frequently we're updating the health data file.

TROUBLESHOOTING BASICS

1. Basically any adjustments you make to the .sh, just reboot the Pi instead of restarting the service.
2. systemctl status birdfeeder-audio.service should tell you what's going on if there are any errors.

Future Plans

I still need to evaluate power usage and heat tolerance to build a more rugged enclosure, or potentially even migrate away from the Pi Zero hardware. I also need to evaluate the audio quality with a better microphone setup (preferably not USB), but a bird or a cat literally stole my RODE mic a while back. I'm sure there's more.