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Re: A Big Proposal: A way to control quality/resolution/framreate/simulcast/layering with RtpSender

From: Chris Wendt <chris-w3c@chriswendt.net>
Date: Wed, 19 Feb 2014 23:32:10 -0500
Cc: Peter Thatcher <pthatcher@google.com>, "public-orca@w3.org" <public-orca@w3.org>
Message-Id: <0C08B038-DAF0-4196-9F8D-8429BF87D8F7@chriswendt.net>
To: Martin Thomson <martin.thomson@gmail.com>

Maybe Iím reading more into this or maybe Iím making it more complex than necessary, or maybe iím stating the obvious, but I think this makes sense.

My originally assumed premise was that you setup a stream with a set of parameters and let the implementation map those parameters to video encoder rate controls and it runs happily along independently doing adaptive bitrate things within the context of the given parameters.

Taking things to the next level, we can imagine having and likely requiring application level control, particularly for SVC and simulcast or in cases where you have multiple RTPSenders, where we need to control across multiple potentially unrelated and independent media streams and based on some metrics feedback that, for example, quality is suffering given some bitrate constraints, so I should switch to half resolution, or no longer send the 3rd enhancement layer or reduce the number of RTPSenders.

So what would be the feedback mechanism here?  Is this up to the application developer to monitor metrics themselves if even possible or practical?

I would propose we think about providing callback hooks based on things like min/max bitrate and min/max quality thresholds.  And maybe specifically define the basic set. 

Again, I think the current discussion around the simple set of parameters satisfies the static config case, but when we talk about max or min type of parameters, I think there needs to be some feedback to notify that application when the min/max point is reached so it can act appropriately.


On Feb 19, 2014, at 6:52 PM, Martin Thomson <martin.thomson@gmail.com> wrote:

> On 19 February 2014 15:44, Peter Thatcher <pthatcher@google.com> wrote:
>> I think we still need scale for simulcast and maxBitrate for cases where you
>> want to constrain bandwidth even when it's available.    And priority vs.
>> resources seems pretty similar.
> I'd like to take simulcast out actually.  I think that aside from some
> bindings necessary to get playback right, you can achieve simulcast
> transmission (what we are talking about here) by having multiple
> tracks with different resolution constraints.  I don't think that
> means fewer options sadly.
> Maybe we can also discuss minimums.  I don't think that it's
> worthwhile having minimum values initially, and maybe not ever, though
> I'm open to the idea.  And I think that it's a universally applicable
> thing across all axes.  I can see cases for minimums on all three:
> frame rate (sign language), resolution (1x1, my image recognition
> can't deal), and quality (my eyes, ow, my eyes).
Received on Thursday, 20 February 2014 04:32:41 UTC

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