Charles Eliot (charle@Exchange.Microsoft.com)
Wed, 13 Dec 2000 17:05:01 -0800
One problem with G.726 is that Windows desktops neither source nor sink
it, so you are looking at several unpleasant alternatives: (1) convince
Microsoft to ship G.726 codecs in some future product and wait for
everybody to install it; or (2) convince every UM vendor or email client
vendor to install a G.726 codec on machines; or (3) burden VM and UM
servers with transcoding burdens.
G.726 was an OK option when the problem was limited to server-to-server
interop, but is not a good option when the (explicit) problem is to
facilitate desktop-to-desktop voicemail.
-----Original Message-----
From: Martin Dragomirecky [mailto:mxd@cisco.com]
Sent: Wednesday, December 13, 2000 10:13 AM
To: Brian Cruickshank
Cc: Charles Eliot; Anthony Baxter; IETF VPIM List
Subject: Re: [VPIM] RE: 3GPP-T-WG3 codecs
would g.726 32k be another option, one virtue being compat w/ vpim 2?
> Brian Cruickshank wrote:
>
> To me, there are the following pros/cons to G.711 and MS-GSM:
>
> Advantages to MS-GSM:
> - Less Storage Space
> - Faster to download to client
> - Faster to send between servers
>
> Advantages to G.711:
> - Better Voice Quality
> - "Universal" Client Support
> - Fewer MIPs / lower complexity / easy to implement
>
> Storage Space:
> With 72Gig drives available and storage capacity following Moore's
Law, I
> think it is fair to say that the 'Less Storage Space' argument will
become
> less and less of a factor over time. I understand that there are size
limits
> on mailboxes which come into play but if this is of paramount concern
then
> perhaps the Unified Messaging vendor would want to transcode into a
lower
> bitrate format than MS-GSM (e.g G.729A, G.723.1, etc.). If the VPIM
codec was
> G.711 then this would be more easily accommodated than if it was
MS-GSM, and
> with better voice quality.
>
> Download to Client:
> Because G.711 is such a light-weight codec in terms of the CPU
required to
> convert 16b linear to / from G.711, vendors can easily transcode VPIM
messages
> into whatever codec they prefer for downloading messages to
low-bandwidth
> clients. If the preferred client codec is MS-GSM, then the 'Fewer
MIPS'
> advantage for G.711 is nullified but if the preferred client codec is
NOT
> MS-GSM (e.g. it could be G.723.1 for a Voice over IP connection) then
the
> 'Fewer MIPs' and 'Voice Quality' advantages for G.711 become even more
> important.
>
> Faster to Send Between Servers:
> To me, the strongest argument for MS-GSM is that it takes ~ 1/4 of the
> bandwidth to send an MS-GSM encoded voice message between 2 universal
> messaging servers than it takes to send a G.711 encoded message.
This
> translates into a lower operational cost to the service provider.
With the
> 'cost per managed bit' dropping in half every 9 months, however, this
may not
> be a significant factor for very long.
>
> I think that the main advantages of G.711 - ease of implementation,
universal
> client support and better voice quality - will make it simpler for
vendors to
> adopt and will keep the intelligibility of voice messages high.
>
> Brian Cruickshank
> Nortel Networks
>
> -----Original Message-----
> From: Charles Eliot [mailto:charle@Exchange.Microsoft.com]
> Sent: Tuesday, December 12, 2000 8:12 PM
> To: Anthony Baxter
> Cc: IETF VPIM List
> Subject: RE: [VPIM] RE: 3GPP-T-WG3 codecs
>
> The ability to take voicemail offline, ie to download onto your laptop
> and read/reply without an active connection, has been one of the most
> compelling scenarios for unified messaging adoption by corporate road
> warriers. I'll try to dig up reference studies.
>
> -----Original Message-----
> From: Anthony Baxter [mailto:anthony@interlink.com.au]
> Sent: Wednesday, December 13, 2000 3:21 AM
> To: Charles Eliot
> Cc: IETF VPIM List
> Subject: Re: [VPIM] RE: 3GPP-T-WG3 codecs
>
> >>> "Charles Eliot" wrote
> > Turns out - after much sighing and gnashing of teeth - that there is
> no
> > patent issue. MS-GSM implements the GSM codec, and the proposed RFC
> > describes how to format a GSM bitstream in such a way that the
MS-GSM
> > codec can read it.
> >
> > The balance between file size and desktop ubiquity is always going
to
> be
> > tricky. I'm leaning these days towards G.711, but as Eric Burger
> pointed
> > out there is still a lot of slow-link dialup going on out there.
>
> As I mentioned in my last mail, though - surely this is more of an
> issue for real time voice, like a phone call, rather than
> store-and-forward
> as for voicemail?
>
> If you are working with low bandwidth clients, I see no reason why
> you couldn't offer a voicemail listen page (say, in a webmail type
> situation) that sends the data in a more compressed format - has
> there been any studies done on how many of those low-bandwidth users
> will actually be pulling their email down to their local PCs, versus
> leaving it on a webmail service (hotmail, or whatever)?
>
> Anthony
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