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Re: [Bug 22209] "each key MUST be a valid registered constraint name in the IANA-hosted RTCWeb Media Constraints registry"

From: Jan-Ivar Bruaroey <jib@mozilla.com>
Date: Tue, 05 Nov 2013 19:45:12 -0500
Message-ID: <52799118.1010206@mozilla.com>
To: public-media-capture@w3.org
On 11/5/13 12:24 PM, Harald Alvestrand wrote:
> On 11/05/2013 06:20 PM, bugzilla@jessica.w3.org wrote:
>> https://www.w3.org/Bugs/Public/show_bug.cgi?id=22209
>>
>> Giri Mandyam <mandyam@quicinc.com> changed:
>>
>>             What    |Removed                     |Added
>> ----------------------------------------------------------------------------
>>                   CC|                            |mandyam@quicinc.com
>>
>> --- Comment #5 from Giri Mandyam <mandyam@quicinc.com> ---
>> We discussed vendor-specific constraints during the F2F at TPAC 2012
>> (http://lists.w3.org/Archives/Public/public-media-capture/2012Dec/att-0196/minutes-2012-10-30.html).
>>
>> I believe what reflected consensus was that vendor-specific constraints be
>> added to the IANA registry, which would allow such constraints to undergo
>> expert review as per RFC 5226.  We can reconfirm this at the next F2F however.
>>
>> On a related note, I do believe the spec is unclear as to what the
>> implementation should do when a valid IANA-registered vendor-specific
>> constraint is provided to MediaStreamTrack.applyConstraints() that the
>> implementation does not recognize or support.

Why differentiate unknown from unsupported?

Constraints constrain, so if our browser hasn't heard of your mandatory 
constraint, then we don't support what you want, which is what you 
wanted to know, which is why we fire the error callback to you. Mission 
accomplished. We don't need IANA for that. - The browser just has to 
recognize what it knows and object to or ignore what it doesn't know here.

IANA registration is a good process for knowing what to implement, not 
for knowing what to support rejection of, because a new constraint may 
be registered tomorrow.

>> I assume an exception can be
>> raised, but I did not find specific guidance in the latest working draft.  The
>> constrainable interface proposal also defines an error callback on
>> applyConstraints().
>>
> I believe the desired behaviour is 100% clear.
>
> If the constraint is mandatory, the applyConstraints() fails.
> If the constraint is optional, the constraint is ignored.

I agree. It is the error callback in step 4 - 
http://dev.w3.org/2011/webrtc/editor/getusermedia.html#methods-4

.: Jan-Ivar :.

> Jan-Ivar and I have been exchanging mail on how to express that in
> WebIDL form.
Received on Wednesday, 6 November 2013 00:45:40 UTC

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