reccon 🦝

Continuously record audio, segmenting against silence and (optionally) uploading audio to GCS.

Motivation

I created this to continuously record the output from my piano, which is useful to me for a number of reasons:

If I improvise something interesting, but then can't quite remember exactly what it was that I played, I can look back at my "replay buffer" to hear it again. Particularly useful for dense jazz voicings, extensions, and alterations.
If I'm practicing a section of a piece of music, and I'm especially satisfied with one playthrough, I can check back to analyze exactly what it was in my playing that sounded good to me. Particularly useful when I'm working on interpretation more than technique, and when the piece has flexibility in terms of rubato, dynamics, articulations, or even local rhythms.
If I do specifically intend to play and record something, I can just sit down and play it and grab the recording later, which is easier than setting up and managing a recording session.

I recommend connecting your computer's audio line-in directly to the line-out of an electronic instrument, so that you're only recording that instrument's output and not any conversations or other ambient sounds. For privacy reasons, I recommend against using a microphone. If you do choose to use a microphone, be sure to communicate to anyone in the area that their voice will be recorded.

Runtime dependencies

You must have SoX installed; the sox, soxi, and rec binaries should be on your path. Most Linux-based distributions provide SoX under the sox package.

Building

This project uses the standard Rust toolchain:

$ cargo test
$ cargo build --release

Usage

In simplest form, just run the program with no arguments. It'll record FLAC files into /tmp/recordings (or your system's $TMPDIR).

You can add a configuration file reccon.toml in the TOML format to customize behavior:

Set storage_dir to change the directory into which recordings will be stored. Note: reccon assumes that it owns this directory and will manage all its contents. If you have unrelated files in this directory, they may be overwritten or deleted.
Set threshold to a float between 0.0 and 1.0 to specify how loud the audio needs to be to start recording. Audio below this threshold counts as silence. This is a linear value, so (e.g.) use 0.01 for a power measurement of −40 dBFS.
Set gcs_bucket to a string like gs://my-bucket or gs://my-bucket/my-prefix/ to automatically upload recorded segments to Google Cloud Storage. If this is set, then the host machine must have GCS credentials, either ADC credentials at the well-known path or service account credentials pointed to by the GOOGLE_APPLICATION_CREDENTIALS environment variable.

To use a configuration file other than ./reccon.toml, pass its path as the sole command-line argument.

Installation on a dedicated system

This is my best-effort recollection of how to get this thing working on a dedicated Raspberry Pi (I use a first-generation Zero W). I'm assuming that the Pi is reachable as raspiano on your network.

First, build for ARM (not ARMv7) and ship over the binary:

cross build --release --target arm-unknown-linux-gnueabihf
rsync --info=progress2 target/arm-unknown-linux-gnueabihf/release/reccon pi@raspiano:~/reccon

(I use rsync and not scp because it works better even when the remote program is currently being executed, instead of failing with ETXTBSY.)

Follow the instructions at https://superuser.com/a/1045885 to disable the on-board sound card and use the USB DAC by default:

# follow instructions at https://superuser.com/a/1045885
echo blacklist snd_bcm2835 | sudo tee -a /etc/modprobe.d/blacklist-snd_bcm2835.conf
sudo sed -i -e '/snd-usb-audio index=-2/ s/^/#/' /lib/modprobe.d/aliases.conf

Create a systemd unit file in /etc/systemd/system/reccon.service:

[Unit]
Description=Continuous audio recorder
After=network-online.target sound.target
Wants=network-online.target sound.target

[Service]
ExecStart=/home/pi/start.sh
WorkingDirectory=/home/pi
User=pi
Group=pi

[Install]
WantedBy=multi-user.target

Create the systemd symlinks:

sudo systemctl enable reccon

It should now launch on boot. Use systemctl restart reccon to poke it. I've had lots of issues with it nondeterministically sometimes not starting or starting but then failing because it doesn't see the sound card. I don't know if that's because ALSA doesn't recognize the sound card if it was plugged in at boot (sometimes), or because reccon / rec(1) starts before ALSA. I just recently added the sound.target unit to the After= and Wants= and am hoping that this helps.

Etymology

It's called reccon because it records continuously.

wchargin / reccon