Audio Streamer for LicheeRV Nano boards with a mems microphone

I created this in a few hours as a test of gemini-cli. I coded no part of this. I only altered this paragraph by hand. Everything else was created by gemini-cli. My coding system is a mac air, the compile system is a LicheeRV Nano (https://www.amazon.com/dp/B0DGL82524) running Debian 13 Trixie (https://github.com/scpcom/sophgo-sg200x-debian). This is a minimal C application (11k) that captures audio from the mems microphone using ALSA and streams it over HTTP. The audio is streamed as raw, lossless LPCM data.

Dependencies

You build this on the LicheeRV Nano. You need to have build-essentials and the ALSA library development package installed. On Sophgo sg200x Debian you can install it with:

sudo apt-get update
sudo apt-get install build-essential libasound2-dev

Building

To build the application, run:

make clean  # to erase the binary that comes with the repo
make

This will create an executable file named audio_streamer.

Running

To run the server, execute the compiled binary:

./audio_streamer

To run the server as a daemon (in the background), use the -d flag:

./audio_streamer -d

The server will start listening on port 8080. It will print a message to the console indicating that it's running.

Listening to the stream

You can listen to the audio stream using a media player that supports raw LPCM streams over HTTP, such as VLC.

To do so in VLC:

1. Open VLC.
2. Go to "Media" -> "Open Network Stream...".
3. Enter the URL of the stream: http://<server_ip>:8080, where <server_ip> is the IP address of the machine running the audio_streamer.
4. Click "Play".

You should now be able to hear the audio from the microphone.

Note: On OSX in Chrome, I can also load the ip directly in the browser and get a player.

How it works

The server listens for incoming TCP connections on port 8080. When a client connects, it forks a new process to handle the client. This child process opens the default ALSA capture device (hw:0,0), sets the audio parameters (48kHz, 16-bit Little Endian, mono), and starts reading audio data.

The audio data is sent to the client with an HTTP header that specifies the content type as audio/wav. A 44-byte WAV header is sent at the beginning of the stream, which allows clients like VLC to correctly interpret the audio format.

Stopping the server

If you are running the server in the foreground, you can stop it by pressing Ctrl+C.

If you are running the server as a daemon, you can find its process ID (PID) and kill it:

ps aux | grep audio_streamer
kill <PID>