Enable playout-delay extension + NACKs + janus version bumps

[danstiner]

This is not meant to merge as-is, but I wanted a place to coordinate rolling out the janus-ftl-plugin changes I've been making and we've been discussing over on Glimesh/janus-ftl-plugin#135. (edit: those changes have merged) This follows my original plan in Glimesh/janus-ftl-plugin#126 (comment)

This specifically targets what changes need to happen to turn on the playout-delay extension from Glimesh/janus-ftl-plugin#134, because it involves a few things:

• Janus must be built with a patch applied to support the playout-delay extension. For convenience I have a branch ready based on Janus v0.11.6 in my fork of janus-gateway
• Then the ftl plugin must be built with janus_playout_delay_support=true
• This enables support, but the ftl plugin will not actually send playout-delay values by default. You still have to set env variables FTL_PLAYOUT_DELAY_MIN_MS and FTL_PLAYOUT_DELAY_MAX_MS to reasonable values.

I totally support your idea to deploy this to just one server to start with (note playout-delay is only meaningful on edge servers though). After deploying I'd want to verify:

• In chrome://webrtc-internals/, the value of jitterBufferDelay/jitterBufferEmittedCount_in_ms should never really dip below the configured min playout delay
• Check if Large keyframes can result in consistent freezes on every keyframe janus-ftl-plugin#101 is mitigated. Ideally verify for the same stream that an unpatched edge node repros the issue and a patched edge node does not repro. My usual test stream is a white noise background with a small moving clock etc
• Run a stream over a lossy network to an ingest with NACKs enabled and an edge with playout-delay enabled. Compare the packet NACK and loss rates to the same content streamed to an ingest with NACKs enabled and a "legacy" edge node without playout delay enabled. Hopefully packet loss rate goes down while the NACK rate remains about the same. If the loss rate gets worse I'd be concerned.
• Let the change sit for awhile and see if anyone reports issues.

While this does implicitly bump the janus version and libsrtp version, there was not impact I saw or expected from that, just keeping up with dependencies.

[clone1018]

and my patch of Janus should be pulled from https://github.com/danstiner/janus-gateway/tree/rtp-playout-delay-extension over to https://github.com/Glimesh/janus-gateway (I don't have permission to that repo)

I've added maintainer permissions for the "Video" team in all video related repositories, let me know if this works!

[danstiner]

Thanks! I think it worked. I pushed the patched branch over and just merged Glimesh/janus-ftl-plugin#136 so I think everything is in place now.

I don't have a way to test these ansible changes so no guarantees they work, but they should be close.

[LukeHandle]

Syntactically things look okay.