Remove track/stream stats in favor of RTCMediaHandlerStats.mid

[jan-ivar]

@karthikbr82 said in #361 (comment):

if we are moving "tracks" [to the] Obsolete stats section then we could do the same for "stream".

👍 I suspect "stream" stats existed to help locate relevant stats from a media starting point. This made sense when pc.addStream was the media hand-off API. E.g.

pc.addStream(stream);
await negotiate();
const stats = await pc.getStats();
const streamStat = [...stats.values()]
  .find(stat => stat.type == "stream" && stat.streamIdentifier == stream.id);
const [senderStat] = streamStat.trackIds.map(id => stats.get(id));

These days, it's probably more helpful to start from a track:

pc.addTransceiver(track);
await negotiate();
const senderStat = [...(await pc.getStats()).values()]
  .find(stat => stat.type == "sender" && stat.trackIdentifier == track.id);

But the track isn't stable (may be changed with replaceTrack); the transceiver.mid is. So better:

const transceiver = pc.addTransceiver(track);
await negotiate();
const senderStat = [...(await pc.getStats()).values()]
  .find(stat => stat.type == "sender" && stat.mid == transceiver.mid);

Of course transceiver.sender.getStats() works, but sometimes we need to navigate the big one.

[henbos]

TPAC decision: remove "track" and "stream" stats in favor of "mid"; don't need to add streamIdentifiers because that is knowable by other means and not very relevant to stats (if someone want that that should be filed separately).

[henbos]

This issue will be inblocked by #498 which exposes the mid on the "transceiver" stats.

[henbos]

Not sure which PR, but the "stream" stats have already been made obsolete (link) and making "track" obsolete is tracked in issue #479. Closing this one.