Re: [MMUSIC] Review of 4566bis

Paul Kyzivat <pkyzivat@alum.mit.edu> Tue, 02 June 2015 16:10 UTC

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Date: Tue, 02 Jun 2015 12:10:20 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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To: Christer Holmberg <christer.holmberg@ericsson.com>, Roni Even <ron.even.tlv@gmail.com>, "mmusic@ietf.org" <mmusic@ietf.org>
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Subject: Re: [MMUSIC] Review of 4566bis
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On 6/2/15 11:24 AM, Christer Holmberg wrote:
> Hi,
>
>>>> I do not think that general media level overrides session level value
>>>> works for the b= attribute Roni
>>>
>>> b= is not an attribute :)
>>>
>>> Anyway, my suggestion would be that the DEFAULT RULE for all SDP elements that can occur both on
>>> session and media level should be that the media level overrides the session level. Then, in cases where
>>> it does not apply, it should be explicitly stated.
>>
>> I do think this *would have been* the right thing to do from the beginning. But I am uncertain
>> if it is the right thing to do *now*, for backward compatibility reasons.
>>
>> Before doing so we will need to do an exhaustive study of all current attribute definitions that are registered
>> in IANA as valid at both session and media level - to ensure that their meaning won't be changed by this.
>
> I agree.
>
> And, I am not saying we shall apply the media-overrides-session rule to all attributes - I am saying that it needs to be clear to which attributes the rule applies, and to which it doesn't.
>
> Leaving it unspecified will not bring compatibility, and the whole purpose of a bis is to correct bugs and clarify things which are unclear :)
>
> I would assume that, in most cases, the media-overrides-session rule DOES apply.
>
> And, we must make sure that, when new attributes are defined, it is indicated whether the rule applies or not.

OK. I agree with all this.

	Thanks,
	Paul


> Regards,
>
> Christer
>
>
>>> -----Original Message-----
>>> From: mmusic [mailto:mmusic-bounces@ietf.org] On Behalf Of Paul
>>> Kyzivat
>>> Sent: 31 May, 2015 8:43 PM
>>> To: mmusic@ietf.org
>>> Subject: Re: [MMUSIC] Review of 4566bis
>>>
>>> On 5/31/15 9:38 AM, Christer Holmberg wrote:
>>>
>>> Good list Christer!
>>>
>>> I have comments on a few of your issues:
>>>
>>>> Q6_2:
>>>>
>>>> In some of the sub-sections, it is indicated that a media-level
>>>> attribute value overrides a session-level attribute value. As far as
>>>> I know, that applies to all attributes (that can be present both on
>>>> the session-level and media-level), so there should be a generic
>>>> statement about that.
>>>>
>>>> This is similar to the comment on the c= line.
>>>
>>> I used to think this, but I think there are some exceptions. (But I
>>> don't
>> offhand
>>> remember what they are.)
>>>
>>>> Section 6.7:
>>>>
>>>> ---------------
>>>>
>>>> Q6-7_1:
>>>>
>>>> The text says:
>>>>
>>>>       "If any one of these appears in a media section then it applies
>>>> for
>>>>
>>>>       that media section.  If none appear in a media section then the
>>>> one
>>>>
>>>>       from session level, if any, applies to that media section."
>>>>
>>>> There should be a general statement in the draft about session level
>>>> information applying to the media level.
>>>
>>> I wish there could be a general statement, but it is hard, given
>> exceptions.
>>> Perhaps there could be a general statement with note that it can be
>> overridden
>>> in particular cases.
>>>
>>> But in any case, *this* is different, because it says that the
>>> presence of
>> any
>>> *one* of four different attributes at media level overrides the
>>> presence
>> of any
>>> one of those four at session level.
>>>
>>>> Section 6.11:
>>>>
>>>> -----------------
>>>>
>>>> The text says that the attribute "specifies the language" of the
>>>> session description.
>>>>
>>>> There has been some confusion about what that really means, so I
>>>> think it would be good to clarify that it applies to any textual
>>>> information that may be provided within the description.
>>>>
>>>> It would also be good to explicitly indicate that the attribute is
>>>> not related to languages used in the actual media streams.
>>>
>>> +1
>>>
>>> 	Thanks,
>>> 	Paul
>>>
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>
>