Re: [rtcweb] Comments to use-cases/reqs document

Stephan Wenger <> Tue, 12 July 2011 15:09 UTC

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Date: Tue, 12 Jul 2011 08:09:20 -0700
From: Stephan Wenger <>
To: Harald Alvestrand <>
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Thread-Topic: [rtcweb] Comments to use-cases/reqs document
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Subject: Re: [rtcweb] Comments to use-cases/reqs document
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That's fine, but then you need to add at least one more use case:
point-to-point, and not quite simple...

On 7.12.2011 08:02 , "Harald Alvestrand" <> wrote:

>On 07/12/11 16:35, Stephan Wenger wrote:
>> Hi Harald,
>> If you define "simple" as "minimum functionality", then there should
>> be a use case "not quite so simple; offer at least the user experience
>> get from a Skype client today".  That use case may well turn out to be
>> more popular than the "simple" use case according to your definition.
>> However, my preference would be not to assume minimalistic use cases,
>> rather tune the level of mandation of the requirements.  (So I'm in
>> Stefan's camp -- keeping the number of use cases reasonable)
>I'm all for "reasonable", but my "reasonable" may be different from
>yours.... the sum of all requirements should indeed allow us to build
>equivalents to Skype or Google Talk on top of this platform (except for
>the parts that don't make sense, of course :-) ), but I find it easier
>to talk about auto-zoom to keep head size constant (for instance - at
>least one Skype beta supported that) as a separate use case, not merged
>with the "basic use case".
>> Stephan
>> On 7.12.2011 07:17 , "Harald Alvestrand"<>  wrote:
>>> On 07/12/11 13:58, Stefan Håkansson LK wrote:
>>>>>> All,
>>>>>> some comments to
>>>>>> ements/?include_text=1>
>>>>>> 3. The "Video Size Change" use case derives F22; but that is already
>>>>>> derived in "Simple Video Communication Service". I propose to remove
>>>>>> the "Video Size Change" use case.
>>>>> I disagree with this proposal.
>>>>> While the "resizing" requirement is in "simple video communication
>>>>> service" as
>>>>> "The users can change the display sizes during the session", I
>>>>> the basic use case does not derive the requirement that the change in
>>>>> video size be communicated to the other party.
>>>>> I would propose the following changes:
>>>>> - Reinstate the text below:
>>>>> 4.2.4.  Video Size Change
>>>>>  Description
>>>>>      Alice and Bob are in a video call in their browsers and have
>>>>>      negotiate a high resolution video.  Bob decides to change the
>>>>> of
>>>>>      the windows his browser is displaying video to a small size.
>>>>>      Bob's browser regenerates the video codec paramters with Alice's
>>>>>      browser to change the resolution of the video Alice sends to
>>>>>      the smaller size.
>>>> My preference is always to keep the number of use cases down.
>>> We may have a difference of style here - I prefer to have explicit use
>>> cases that show only a single action or attribute that needs to be
>>> supported, which means that the number of use cases tends to be high.
>>> I think this is especially important for the situation where a WG has
>>> decide to drop an use case because no agreed-upon implementation can be
>>> found.
>>>>    Could we not just add a sentence to the current "Simple Video
>>>> Communication Service" use case so it reads something like "The users
>>>> can change the sizes of the video displays during the session. Changes
>>>> of the display size are communicated from the displaying browser to
>>>> one sending the stream so that the video codec parameters can be
>>>> accordingly."
>>> As per above - I would prefer the "Simple Video Communication Service"
>>> to be as simple as possible. Even resizing the window locally is more
>>> than "as simple as possible" - the Gtalk video client for my phone
>>> doesn't support that.
>>>> But my preference is not strong - I'm happy to reinsert the use case
>>>> people think so.
>>>>>  Derived Requirements
>>>>>      F22 ( It SHOULD be possible to modify video codec parameters
>>>>> during a
>>>>>      session.)
>>>> F22 now reads "The browser SHOULD use encoding of streams suitable for
>>>> the current rendering (e.g. video display size) and SHOULD change
>>>> parameters if the rendering changes during the session"
>>>>> - Change the text of F22 to be:
>>>>>     It SHOULD be possible for one party to request a change in video
>>>>> codec parameters, such as size,
>>>>>     during a session, and for the other party to react to this
>>>> I think "party" is very vague. What does it mean - the browser, the
>>>> user, the web app?
>>> Since this is the IETF WG - the "party" is the browser, user and web
>>> together; somehow the desire for a change has to be communicated across
>>> the network, and that's the requirement I think needs to be in the IETF
>>> requirements list.
>>> The corresponding API requirement (which I'm not sure how to formulate
>>> all this may go on in the browser and need no explicit API) needs to go
>>> into the W3C requirements list.
>>> _______________________________________________
>>> rtcweb mailing list