Charles,
Maybe we should use G.723.1 for guidance. There is a single G.723.1 capability, although there are two rates (and two distinct encodings, unlike G.729/G.729a) which are signaled in-band. All decoders are required to support both rates. The only place in H.245 where the rates are distinguished is in the RequestMode message.
It seems to me, however, that the decision to encode G.729 versus G.729a should always be local, since the major impact, complexity and therefore CPU usage, is local. Otherwise, the remote EP would always want to receive the higher-quality audio of G.729.
Paul Long Smith Micro Software, Inc.
-----Original Message----- From: Hutton, Charles [mailto:charles.hutton@ATTWS.COM] Sent: Wednesday, March 01, 2000 12:24 PM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: Errors / ambiguities / problems found in specs at last week's int erop
Paul:
729 and 729A do indeed use the same encoder. Only the decoder is different. Performance of 729A is poorer, particularly with respect to tandeming.
I can see that it may sometimes be beneficial to control whether the 729 or 729A algorithm (if a choice is available) is used by the decoder in order to prevent significant degradation of audio quality. If that is a real scenario, then it becomes more than "a local issue".
Perhaps others can comment on the "realness" of this possibility.
Charles (Chuck) Hutton Strategic Architecture Engineering Wireless Local Technology Group AT&T Wireless Services PO Box 97059 Redmond, WA 98073 (USPS only) 9461 Willows Road Redmond, WA 98052 (FEDEX/UPS) 425-702-2938 Voice 425-702-2518 FAX charles.hutton@attws.com