Latest version of Chrome not including `a=msid`

[se...@pion.ly]

I have been getting a lot of bug reports into Pion about this.

Does anyone have a crbug, was this a planned deprecation? 

Chrome Media Section

```

m=audio 9 UDP/TLS/RTP/SAVPF 111 9 0 8
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:MfuH
a=ice-pwd:fig1ADQ0ADTtEMWH77NptwLz
a=ice-options:trickle
a=fingerprint:sha-256 36:D4:A4:44:0A:D5:97:8E:D4:6F:32:80:2A:87:F1:59:D1:8C:10:53:03:B1:4F:44:D7:4B:10:0E:2E:AA:CE:64
a=setup:active
a=mid:1
a=extmap:1 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
a=sendonly
a=rtcp-mux
a=rtpmap:111 opus/48000/2
a=rtcp-fb:111 transport-cc
a=fmtp:111 minptime=10;useinbandfec=1
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=ssrc:352663822 cname:uljllCW8U9c39XGw

```

[se...@pion.ly]

This seems to only happen when Offer is a `recvonly` transceiver. I will have a jsfiddle shortly that shows the behavior difference

[se...@pion.ly]

Here is a jsfiddle that exhibits the behavior https://jsfiddle.net/6jrypdez/9/

[se...@pion.ly]

I found the relevant crbug[0]

Adding `a=msid-semantic: WMS*` causes Chrome to respond with a `a=ssrc *msid*` line now.

[0] https://issues.chromium.org/u/1/issues/328522463?pli=1

[Philipp Hancke]

If you still rely on the plan-b ssrc specific msids you should stop doing that now

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[Sean DuBois]

Thanks Neil! What values should I be using?

Looking at the docs distributed by Google https://docs.google.com/document/d/1-ZfikoUtoJa9k-GZG1daN0BU3IjIanQ_JSscHxQesvU/edit#heading=h.wuu7dx8tnifl 

The following values are in the example unified plan offer

```

a=ssrc:11 cname:cname

a=ssrc:11 msid: track-id-2

a=ssrc:11 mslabel:

a=ssrc:11 label:track-id-2

```

How should I be determining the MediaStreamTrackId instead?

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[Philipp Hancke]

That document  is pretty outdated (as any doc not containing a name). RFC 8829 recommends looking for a=msid:stream (no space there) but ignores that due to backward compat with existing software it is advisable to include the track id too. And OFC does not consider that there is no way to distinguish that from "legacy" software that does not include msid at all...

Harald: can you do a semi-hostile doc takeover

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