mtsRTC

mtsRTC is the XLTD-maintained olcRTC fork used for MTS Link carrier work. It stays close to olcRTC refactor/universal-carrier, but carries the MTS Link guest-bot and H.264/SEI transport patches required by XLTD VPN.

Branches

Branch	Purpose
mtslink-universal-carrier	Current production fork used by XLTD VPN builds.
refactor/universal-carrier-mtslink	Older integration branch kept for reference.

The repository default branch should remain mtslink-universal-carrier while this fork is the active XLTD VPN core.

What This Fork Adds

• auth.provider: mtslink.
• MTS Link room resolution for permanent /j/{userId}/{eventId} URLs and expanded /stream-new/{sessionId} URLs.
• Guest bootstrap flow: prejoin cookies, guest login, login lookup, connection/conference creation, SFU token extraction, peer update, pinning, and silent Opus RTP.
• H.264 media shape expected by MTS Link rooms.
• Recommended mtslink + seichannel + multipath VPN mode, carrying olcRTC data inside H.264 SEI payloads across several independent guest-bot lanes.
• videochannel legacy/diagnostic mode for visible QR/video experiments.
• Quick server/client scripts with a 5) mtslink menu entry.
• XLTD VPN compatible olcrtc://... URI output.

Quick Start

chmod +x script/*.sh
./script/srv.sh --no-cache

Choose carrier 5) mtslink, paste the MTS Link room URL, and copy the printed URI into XLTD VPN.

Recommended client/server transport:

mtslink + seichannel + multipath

Recommended SEI profile:

fps=30
batch=8
frag=700
ack-ms=10000
liveness-interval=20s
liveness-timeout=15s
liveness-failures=6
mc-lanes=12
mc-control-lanes=1
mc-connect-parallel=2
mc-min-ready=4
mc-max-streams-per-lane=3

For wider lab profiles, both sides may use fps=60&batch=64&frag=900&ack-ms=2000&mc-lanes=16&mc-min-ready=8. Leave multipath.lanes unset only for legacy single-lane compatibility.

Full setup and diagnostics: MTSLINK.md.

Recent stability fixes

The mobile API gained the contract the XLTD VPN Android client expects:

• mobile.SetAutoDNS(candidatesCsv, probeHost) string — picks the fastest responding upstream from a comma-separated DNS list, falls back to the first candidate, then to 1.1.1.1:53. Pairs with GetAutoDNSUpstream(). Without these symbols OlcVpnService.runVpnOnce crashed on every start with NoSuchMethodException.
• normalizeTransport now recognises videochannel (and video, vid, video-channel, video_channel). It used to silently rewrite the carrier to vp8channel for any unknown value.
• Check() and Ping() build TransportOptions per transport via buildCheckOptions. SEI probes now pass seichannel.Options, video probes pass nil, VP8/data probes still pass vp8channel.Options. Previously a hard-coded vp8channel.Options value was sent into every transport, which the SEI transport rejected with ErrOptionsTypeMismatch.

Transport-side hardening:

• seichannel remote-track goroutine now polls closed/closeCh at the top of every loop iteration and reads with a 250 ms deadline, bounding the per-goroutine exit latency under reconnect storms.
• internal/engine/mtslink threads a cancellable context through silent-audio pumping, the pin loop, and the shutdown AudioVideoControl call; Pin() is bounded by a 5 s deadline so close cannot strand a 25 s in-flight HTTP.

Build Source Selection

The quick scripts default to the local checkout or unpacked archive. They only download a remote repository when --repo-url=... is provided. This prevents a server rebuild from accidentally falling back to upstream olcRTC without the MTS Link patches.

Remote example:

./script/srv.sh \
  --repo-url=https://github.com/l1ch666/mtsRTC.git \
  --branch=mtslink-universal-carrier \
  --no-cache

Compatibility Notes

• seichannel is the normal MTS Link VPN path.
• videochannel is kept for legacy visible-video diagnostics and requires ffmpeg.
• vp8channel is a legacy probe and is not expected to work reliably in H.264-only MTS Link rooms.
• datachannel is not part of the MTS Link carrier path.