Subject: Re: [AVT] minor improvment to RFC3267

From: Magnus Westerlund <[email-masked]>
Date: Tue, 06 Apr 2004 21:19:56 +0200

Hi Thomas,

Please see comments inline.

Belling Thomas wrote:

> Dear Magnus, all, 
> 
> I would like another minor improvment to RFC3267, that you may consider
> for a possible bis draft. 
> 
> Clause 8.1 now reads: 
> " 
>       mode-set:  Requested AMR mode set.  Restricts the active codec 
>                mode set to a subset of all modes.  Possible values are a
> 
>                comma separated list of modes from the set: 0,...,7 (see 
>                Table 1a [2]).  If such mode set is specified by the 
>                decoder, the encoder MUST abide by the request and MUST 
>                NOT use modes outside of the subset.  If not present, all
> 
>                codec modes are allowed for the session. 
> " 
> 
> The text as it is right now rules out that you use the SID mode 8 in
> combination with a restricted mode set. 

I at least had no intention of excluding the usage of SID together with 
a restricted mode set. I assume that the restricted mode sets in GSM for 
AMR does support the usage of SID + 4 speech modes. So I do not see a 
problem of adding an explicit note that usage of SID is always included.

> 
> As an editorial thing, I also suggest replacing the Reference to Table
> 1a in 3GPP TS 26.101 with an internal Reference to table 1 in the RFC,
> as the information is identical and this enhances the readability.
> 

The reason for not referencing the table has been to avoid any 
divergence between the AMR specification and the payload format. 
Therefore all references in the AMR payload format points on 26.101.

> I would suggest the following improved text, which is in line with the
> usage within 3GPP: 
> " 
>       mode-set:  Requested AMR mode set.  Restricts the active codec 
>                mode set to a subset of all modes.  Possible values are a
> 
>                comma separated list of modes from the set: 0,...,7 (see 
>                Table 1). The SID mode 8 is never included in the mode
> set, but 
>                may always be used.  If a mode set is specified by the 
>                decoder, the encoder MUST abide by the request and MUST 
>                NOT use modes outside of the subset except for mode 8. 
>                If not present, all  codec modes are allowed for the
> session. 
> " 

I would actually change the added sentence to:
The SID mode 8 is never included in the mode set, and MAY always be used.

> 
> A similar change should be done in Clause 8.2 for WB-AMR: 
> " 
>       mode-set:  Requested AMR-WB mode set.  Restricts the active codec 
>                mode set to a subset of all modes.  Possible values are a
> 
>                comma separated list of modes from the set: 0,...,8 (see 
>                Table 1a [4]). The SID mode 9 is never included in the
> mode set, but 
>                may always be used.  If a mode set is specified by the 
>                decoder, the encoder MUST abide by the request and MUST 
>                NOT use modes outside of the subset except for mode 9. 
>                If not present, all  codec modes are allowed for the
> session. 
> " 
> 

Changing it for AMR-WB at the same times seems natural.

Anyone having comments on this?

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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