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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: Sat, 22 Mar 2008 12:02:02 -0400
User-agent: Thunderbird (X11/20080226)

Rick Parrish wrote:
Jeff Brower wrote:
All the standardized codecs that I know of, both ones with IP rights requirements and free ones, provide a reference design, typically fixed-point C code plus test vectors. I wonder why DVSI has not done the same.

Perhaps the APCO and TIA committees did not require it when the algorithm was published ten years ago.



APCO Project 25 has quite a number of standards documents. If you look at a list for vocoders:

ANSI/TIA/EIA 102.BABA Vocoder Description
ANSI/TIA/EIA 102.BABB-A Vocoder Mean Opinion Score (MOS) Test
ANSI/TIA/EIA 102.BABC Vocoder Reference Test
ANSI/TIA/EIA 102.BABD Vocoder Selection Process
ANSI/TIA/EIA 102.BABD Vocoder Selection Process Tapes

I have not looked at these standards to see the level of detail.

There are other parts of the standard that deal with compliance on a system level.

I was recently involved in testing a device to a standard where a third party creates the test suite and grants the certificate.

Using a AMBE or other codec chip is part of the hardware versus software decision. We want to do everything in software but there are limitations. For example, the functions of the Maxim chip used in the USRP DBS tuner could be done in software if there was sampling rates above 4Gsps and the computing power to handle it. A hardware solution is used because of these limitations. Because we can peek into the IMBE black box and know that it can be easily implemented in software we tend to discount a hardware solution. It is much like the situation with the HDTV decoder where current PC hardware can not do all the decoding. If a hardware MPEG-2 decoder was used, then it could be done, but it ruins the all software solution.

73 Eric

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