Re: [rtcweb] [tsvwg] Diffserv QoS for Video

<> Mon, 09 May 2016 07:36 UTC

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Date: Mon, 09 May 2016 09:34:25 +0200
Thread-Topic: [tsvwg] Diffserv QoS for Video
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Subject: Re: [rtcweb] [tsvwg] Diffserv QoS for Video
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Hi Paul,

I've talked with audio/video experts of Deutsche Telekom and they too favored what you recommend below: transport audio and video by the same queue. Your statement below however stops there and the draft text doesn't clarify the issue:

If there's interactive video with audio, then they both should be marked for the same PHB which is:
- EF ?
- AF4? Like AF41 Audio, AF42 Video (AF43 in addition, if P or B frames are to receive a lower priority / 
  higher drop precedence PHB)?

I personally prefer AF4 if audio and video are to be transported in the same queue.

I'd also ask for the draft text to be clear about the issue when to mark audio by the EF PHB. My understanding after reading your statement below is: Audio marked EF if there's no video flow only.

BC>Finally, why is audio not also subdivided into interactive and 
BC>non-interactive? As far as I can see, both are logically possible.

[PJ] For WebRTC, audio alone is "interactive" in nature (which is 
  why it's marked EF).  However, if one is sending audio and video 
  it makes sense to mark them both same way to get the same PHB and 
  hopefully have them queued in the same buffers along the path.  
  Sending audio as EF and possibly having a PHB that results in 
  packets arriving much faster than corresponding video packets 
  marked as AF42 is not at all helpful for applications that have 
  to synchronize the audio and video flows.