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Re: [Discuss-gnuradio] DV Dongle - AMBE USB Device

From: Eric A. Cottrell
Subject: Re: [Discuss-gnuradio] DV Dongle - AMBE USB Device
Date: Wed, 19 Mar 2008 01:37:38 -0400
User-agent: Thunderbird (X11/20070801)

Rick Parrish wrote:
> Eric A. Cottrell wrote:
>> I am also thinking of writing a APCO P25 Voice to AMBE2000 frame
>> converter and see
>> if the device can decode P25 as well.  This may be a general IMBE and
>> AMBE codec.
> I hope so. I looked at this a while back. What concerned me most was
> the AMBE2000/2020 documentation seemed to omit P25 style IMBE
> compatibility. Compare the docs to another DVSI product - the VC55 -
> to see what I mean.

Looking over the docs the VC55 is a P25 only AMBE+ 2 CODEC that only
supports full rate and the proposed (maybe part of standard now) half
rate.  What is good is the mention that the improvements are still
compatible with the P25 vocoder standard.  The AMBE + 2 part sounds like
further improvements to the CODEC over the AMBE2000.  The future
AMBE3000 will implement AMBE + 2 and it appears compatible with the
AMBE2000 and AMBE1000.

The AMBE2000 is more flexible in the data rates and when I look at the
rate tables on page 29 I see the P25 rate listed with the correct voice
and FEC data rates.  You can do the same rate in AMBE or AMBE+.

So one task will be to figure out how to configure the chip so it will
decode P25.

73 Eric

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