📻 racoder

Racoder is a lightweight Node.js web server that leverages FFmpeg to transcode Internet radio and video streams into HTTP MP3 streams. It supports a variety of input stream formats, including HLS, MPEG-DASH, and RTMP – essentially, anything that FFmpeg can handle.

Use cases

• Stream Internet radio streams using different audio codecs (like AAC) to devices that only support MP3 playback
• Play HLS and MPEG-DASH streams on devices that don't support those protocols
• Transcode live video streams into audio only versions

Design goals and trade-offs

• Minimize server requirements
  • Racoder runs inside a container with 256 MB of RAM and consumes very little CPU
• Minimize traffic volume
  • Racoder will only pull from an upstream source during the time a stream is requested
• Aimed at small (private) deployments
  • Each request spawns a separate instance of FFmpeg which consumes additional memory (approx. 20 MB of RAM per active stream) and network bandwidth

Configuration options

Racoder supports two configuration modes (since v2):

1. Single-stream mode: Configure one stream using environment variables
2. Multi-stream mode: Configure multiple streams using a streams JSON file

Single-stream mode

Configuration options are set using environment variables.

Name	Description	Default value	Example
INPUT_STREAM	Required. URL for incoming stream	N/A	https://artesimulcast.akamaized.net/hls/live/2030993/artelive_de/master_v180.m3u8
BITRATE	Transcoding bitrate for output MP3 stream	128k	320k
LOG_LEVEL	Level of detail for log output	INFO	DEBUG
OUTPUT_PATH	URL path for output MP3 stream	/	/my-station
TZ	Timezone for log timestamps	UTC	Europe/Berlin

Multi-stream mode

To configure multiple streams, create a streams JSON file and specify its path using the STREAMS_FILE environment variable. When STREAMS_FILE is set, single-stream environment variables (INPUT_STREAM, OUTPUT_PATH, BITRATE) are ignored.

Multi-stream mode requires Racoder v2.0 or later

Streams file structure

{
  "defaults": {
    "bitrate": "128k"
  },
  "streams": [
    {
      "input": "https://example.com/stream1.m3u8",
      "output": "/stream1"
    },
    {
      "input": "https://example.com/stream2.m3u8",
      "output": "/stream2",
      "bitrate": "192k"
    }
  ]
}

Streams file options:

• defaults (optional): Default values applied to all streams
  • bitrate: Default bitrate for streams that don't specify one
• streams (required): Array of stream configurations
  • input (required): URL for the incoming stream
  • output (required): URL path for the output MP3 stream (must start with /)
  • bitrate (optional): Transcoding bitrate for this specific stream (overrides default)

Environment variables for multi-stream mode:

Name	Description	Default value	Example
STREAMS_FILE	Required. Path to streams JSON file	N/A	/config/streams.json
LOG_LEVEL	Level of detail for log output	INFO	DEBUG
TZ	Timezone for log timestamps	UTC	Europe/Berlin

Examples:

• Simple multi-stream config
• Extended multi-stream config with defaults

How to deploy

Pre-built Docker images for different architectures are available on Docker Hub and the GitHub Container Registry. Deploy using Docker Compose on a small home server like a Raspberry Pi or host it (for free) on fly.io.

Security Note: Examples use --read-only and --cap-drop ALL to run the container with minimal privileges. These are recommended for production deployments.

Using Docker Run

Single-stream mode

Let's use a simple example and deploy an instance on our local client machine:

docker run \
  --rm \
  --read-only \
  --cap-drop ALL \
  --name racoder \
  --publish 3000:3000/tcp \
  --env INPUT_STREAM="https://as-hls-ww-live.akamaized.net/pool_26173715/live/ww/bbc_radio_four_extra/bbc_radio_four_extra.isml/bbc_radio_four_extra-audio%3d96000.norewind.m3u8" \
  paulgalow/racoder:latest

Racoder will serve its output stream at http://<hostname>:3000/. So for this example open http://localhost:3000/ in your browser or media player of choice (like VLC, QuickTime, …) to listen to the output stream.

Here we are using the BBC Radio 4 Extra HLS AAC stream as input, but it does not have to be an audio HLS stream. Streams using MPEG-DASH are supported as well, as are video HLS/MPEG-DASH streams.

Multi-stream mode

To run multiple streams, create a streams file (e.g., streams.json) and mount it into the container:

docker run \
  --rm \
  --read-only \
  --cap-drop ALL \
  --name racoder \
  --publish 3000:3000/tcp \
  --env STREAMS_FILE="/config/streams.json" \
  --volume "$(pwd)/streams.json:/config/streams.json:ro" \
  paulgalow/racoder:latest

With a streams file like this:

{
  "streams": [
    {
      "input": "https://as-hls-ww-live.akamaized.net/pool_26173715/live/ww/bbc_radio_four_extra/bbc_radio_four_extra.isml/bbc_radio_four_extra-audio%3d96000.norewind.m3u8",
      "output": "/bbc-radio-4-extra",
      "bitrate": "128k"
    },
    {
      "input": "https://artesimulcast.akamaized.net/hls/live/2030993/artelive_de/master_v180.m3u8",
      "output": "/arte-de",
      "bitrate": "192k"
    }
  ]
}

Streams will be available at:

• http://localhost:3000/bbc-radio-4-extra
• http://localhost:3000/arte-de

Using Docker Compose

• Single-stream file example
• Multi-stream file example

Using fly.io

• Single-stream simple TOML example
• Single-stream extended TOML example

Monitoring

Racoder provides a /healthcheck endpoint that returns HTTP 200 when the server is running. This can be used for container health checks and load balancer configuration.

Troubleshooting

Debugging

Set LOG_LEVEL=DEBUG to see detailed FFmpeg output and stream processing information.

Common issues

• Stream not starting: Verify the INPUT_STREAM URL is accessible from the container
• High memory usage: Each active client spawns a separate FFmpeg process (~20MB per stream)
• Connection errors: Ensure port 3000 is accessible and not blocked by firewalls