Re: [AVTCORE] WG last call on draft-ietf-avtcore-avp-codecs-01

["Ali C. Begen (abegen)" <[e-mail]>]

-----Original Message-----
From: <Somogyi>, "Gabor   (NSN - HU/Budapest)" <[e-mail]>
Date: Wednesday, March 20, 2013 4:06 PM
To: Keith 'DRAGE <[e-mail]>, Colin Perkins
<[e-mail]>, "[e-mail]" <[e-mail]>
Cc: Magnus Westerlund <[e-mail]>
Subject: Re: [AVTCORE] WG last call on draft-ietf-avtcore-avp-codecs-01

>RFC 1890 (obsoleted by 3551):
>   Audio applications operating under this profile should, at minimum,
>   be able to send and receive payload types 0  (PCMU)  and 5 (DVI4).
>
>Maybe I am a little bit late, as RFC 1890 was finalized in 1996. Still,
>my question is why PCMU should be supported, while PCMA is absolutely
>optional?
>
>As far as I know in traditional telecom networks G.711 u-Law (PCMU) is
>used in North America and Japan only, while A-law is used by the vast
>majority. And when interconnecting A-law and u-Law regions, then A-Law is
>used. That suggests that supporting PCMA is at least as important as PCMU.
>
>Maybe I answered my own question referring to "traditional telecom
>networks". I have no access to VoIP / IMS statistics. What is the usage
>ratio between PCMU and PCMA nowadays? And do you see any firm trend in
>royalty and patent free codec usage, such as Opus? I am just asking,
>because if you plan decades ahead, then writing that a high bandwidth but
>low quality G.711 SHOULD be supported sounds a bit like living in the
>20th century. Well, actually in the pre-1980 era, as on radio networks,
>such as GSM, at least the bandwidth was optimized. And "modern" wireless
>devices, such as 3GPP LTE clients may not support PCMA/PCMU at all, even
>though this RFC draft applies to them. (See 3GPP TS 26.114 section 5.2
>"Codecs for MTSI clients in terminals".)
>
>All in all, I may say that supporting PCMU or PCMA is RECOMMENDED, but
>definitely remove SHOULD.

From 2119 perspective, RECOMMENDED and SHOULD are identical.

>
>BR,
>Gabor Somogyi
>
>-----Original Message-----
>From: [e-mail] [mailto:[e-mail]] On Behalf Of ext
>DRAGE, Keith (Keith)
>Sent: Tuesday, March 19, 2013 6:15 PM
>To: Colin Perkins
>Cc: Magnus Westerlund; IETF AVTCore WG
>Subject: Re: [AVTCORE] WG last call on draft-ietf-avtcore-avp-codecs-01
>
>I'm still confused.
>
>Surely PCMU0 was recommended before this update and is recommended now.
>
>DVI4 was recommended before this update and is now optional.
>
>I guess the result of that is that I can be conformant but implement
>neither, although it will not be a terribly useful implementation.
>
>Regards
>
>Keith
>
>
>
>> -----Original Message-----
>> From: Colin Perkins [mailto:[e-mail]]
>> Sent: 15 March 2013 18:00
>> To: DRAGE, Keith (Keith)
>> Cc: Magnus Westerlund; IETF AVTCore WG
>> Subject: Re: [AVTCORE] WG last call on draft-ietf-avtcore-avp-codecs-01
>> 
>> On 12 Mar 2013, at 16:40, DRAGE, Keith (Keith) wrote:
>> > I'm trying to parse the final sentence of the change made to RFC 3551.
>> >
>> > Essentially this i-d modifies:
>> >
>> > "   Audio applications operating under this profile SHOULD, at a
>>minimum,
>> >   be able to send and/or receive payload types 0 (PCMU) and 5 (DVI4).
>> >   This allows interoperability without format negotiation and ensures
>> >   successful negotiation with a conference control protocol."
>> >
>> > To become:
>> >
>> > "   Audio applications operating under this profile SHOULD, at a
>>minimum,
>> >   be able to send and/or receive payload type 0 (PCMU).
>> >   This allows interoperability without format negotiation and ensures
>> >   successful negotiation with a conference control protocol. Some
>> >   environments MAY make support for PCMU mandatory."
>> >
>> > What the final sentence currently says is that some environments
>>provide
>> an option to make support for PCMU mandatory, which implies that other
>> environments do not provide such an option. Neither of those make sense
>>to
>> me and there I believe that cannot be the meaning.
>> >
>> > I suspect we are looking for sentence that looks more like "Some
>> environments REQUIRE support for PCMU", but I am not sure if there is an
>> "only" floating around in there somewhere.
>> 
>> 
>> I don't think the draft ought to say "only". This sentence looks to be
>> addressing the RTCWeb use case, which makes PCMU mandatory to implement
>> but also allows other codecs.
>> 
>> To my reading, "Some environments MAY make support for PCMU mandatory"
>>and
>> "Some environments REQUIRE support for PCMU" are equivalent, but I have
>>no
>> objection to the change if you think it clearer.
>> 
>> --
>> Colin Perkins
>> http://csperkins.org/
>> 
>> 
>
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