In article ,
Brian Reay wrote:

Remember packet. The AX.25 protocol was open, but it could not really be
changed because that would break compatability between the many
implementations that existed after some time.

Which is something the "anti" AMBE CODEC people ignore.

If the open CODEC happens, their scope to "experiment" with it will be
limited- unless they only want to talk to themselves or with others they've
co-ordinated experiments with.

Seems to me there's plenty of opportunity for flexibility with regards
to codecs. The protocol could be designed to allow for negotiation of
a common codec between two radios - start out with a simple
"universal" codec to get the communication started, and then
optionally switch to a different one.

Something like this is done in the commonest voice-over-IP protocol
family (SIP). There are numerous codecs available, ranging from
bog-standard telephony-style (uLaw and aLaw), to simple linear PCM, to
ADPCM, to various forms of sophisticated coding and compression. Some
of these require paid licenses (e.g. G729), some come with a
commercial- but-free license (e.g. ILBC), some are based on patents
which have now expired and can be implemented freely (e.g. versions of
GSM), and some are aggressively open-source and free-as-in-
speech-and-beer (e.g. Speex).

Protocol negotiation becomes tricker when you're dealing with a
repeater system, or a more-than-two-way simplex conversation, but
that's where the fun and experimentation comes in!

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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