Graham Klyne (GK@dial.pipex.com)
Fri, 06 Aug 1999 08:20:00 +0100
At 11:15 05/08/99 -0700, Blair Whitney wrote:
>For what it is worth, we have a product that uses IMA ADPCM at 32kbps.
>I realize that this codec will not be part of the VPIM spec,
>but it may be nice to allow the proposed MIME tag values to allow this
>codec.
My view is that content negotiation and associated framework exists to
allow new, previously "unknown" capabilities to be introduced.
In the case of audio codecs, it is quite possible that a registry could be
created and the feature tag simply indicates that acceptable values are
from that registry.
I think this could even be done "after the event" -- there are other cases
where a list of options in a standard has later been used to initialize a
new IANA registry.
(BTW, structly speaking, feature tags are not MIME tag values: they can be
used independently of MIME. In this case, the linkage is provided by the
proposed content-features header.)
>This codec usage would be confused with G.726 possibly in:
>>3.5 MIME audio content-types
>>
>> Feature tag name Legal values
>> ---------------- ------------
>> mime-audio audio/32kadpcm
audio/32Kadpcm would be used _only_ if the audio data is not
WAV-encapsulated. I don't know exactly how it is specified, but I would
hope that the spec is tight enough to exclude incompatible alternatives.
>Although it could be resolved with:
>>3.1 Voice codec
>>
>> Feature tag name Legal values
>> ---------------- ------------
>> codec G-726-32
> IMA-32 ???
My take is: the intent here is to indicate a specific codec used within a
generic audio encapsulation framework, such as WAV. In the case of
audio/32Kadpcm, no further clarification of codec may be possible or needed.
If it turns out that such clarification is needed then this tag would
indeed be a possible means to provide it.
In summary: I broadly agree with your comments; mine are added for
(hopefully) clarification.
#g
------------
Graham Klyne
(GK@ACM.ORG)
This archive was generated by hypermail 2.0b3 on Tue Mar 19 2002 - 01:04:17 IDT