Nextcast

A live streaming suite using state of the art protocols to enable low latency and secure audio/video distribution.

Features

• Icecast compatibility (source and/or sink) makes it easy to set up Nextcast alongside existing setups commonly found in online radio broadcasting -- providing an easy path to distribute existing streams over more reliable and secure protocols such as HLS while ensuring continued support for legacy clients.
• Encrypted audio/video ingestion with RIST, an open-source, open-specification, and RTP-compatible protocol designed for reliable transmission over lossy networks with low latency and high quality.
• Built-in web player that automatically connects to the most reliable and secure supported transport. With Javascript enabled (optional), it includes 100+ visualizations for audio-only streams and displays playback history with cover art from Apple Music®, Spotify®, or Last.fm®.
• Currently active and unique listener statistics for the past month, collected for all distribution protocols.

Runtime dependencies

• PostgreSQL >=16.0

Build requirements

• Erlang/OTP and Elixir as specified by .tool-versions
• Node.js and pnpm as specified by package.json

Architecture diagrams

C4-L1¹

┌────────────┐
│   Source   │     ┌──────────┐     ┌───────────┐
│ (eg. RIST, │ ←─→ │ Nextcast │ ←─→ │  client   │
│  Icecast)  │     └──────────┘     |   (HLS)   │
└────────────┘             ↑        └───────────┘
                           |        ┌───────────┐
                           └──────→ │  client   │
                                    │ (Icecast) │
                                    └───────────┘

Supported source protocols (ingestion)

Pulling from other sources

1. ADTS/MP3 from an Icecast or Shoutcast® server
   • Tested with Shoutcast® v1.9.8 and v2.5.1

Pushing to Nextcast

1. RIST (VSF TR-06-2:2021, Main profile)
   • Stream encryption (AES-128-CTR / AES-256-CTR) is required, eg. as secret=$PSK and aes-type=128|256 parameters in the RIST URL. Unencrypted packets will be discarded.
   • Tested with OBS 29.0, FFmpeg 5.1, and libRIST 0.2.7
     • OBS >=28.0, FFmpeg >=4.4, and libRIST >=0.2.0 are also expected to work
2. MPEG-TS over TLS over TCP
   • Tested with FFmpeg 7.0, eg. ffmpeg -i ... -f mpegts -cert_file $CERTFILE -key_file $KEYFILE tls://$IP:PORT
3. ADTS/MP3 over HTTP
   • Tested with a fork of Daniel Nöthen's butt, adding support for Transfer-Encoding: chunked
   • Requires HTTP/1.1
4. Opus via WebRTC (with WHIP)
   • Experimental

Supported sink protocols (distribution)

1. Icecast
2. HLS

Codec support / transcoding matrix

                ┌───────────────+───────────────+───────────────+───────────────┐
          +─────+ MP3           | AAC-LC        | H264 (High 4) | Opus          |
  ┌────┐  | OUT | MPEG-2 Audio  | ADTS          | MPEG-TS       | N/A           |
  | IN |  +─────+ HLS, Icecast  | HLS, Icecast  | HLS           | Icecast       |
┌─+────+────────+───────────────+───────────────+───────────────+───────────────+
| MP3           |               |               |               |               |
| MPEG-2 Audio  |       ✔       |       ✘       |       ✘       |       ✘       |
| Icecast       |               |               |               |               |
+───────────────+───────────────+───────────────+───────────────+───────────────+
| AAC-LC        |               |               |               |               |
| ADTS          |       ✘       |       ✔       |       ✘       |       ✘       |
| Icecast       |               |               |               |               |
+───────────────+───────────────+───────────────+───────────────+───────────────+
| H264 (High 4) |               |               |               |               |
| MPEG-TS       |       ✘       |       ✘       |       ✔       |       ✘       |
| RIST          |               |               |               |               |
+───────────────+───────────────+───────────────+───────────────+───────────────+
| Opus          |               |               |               |               |
| N/A           |       ✘       |       ✘       |       ✘       |       ✔       |
| WebRTC-WHIP   |               |               |               |               |
└───────────────+───────────────+───────────────+───────────────+───────────────┘