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

[Jeff Brower]

Eric-

> 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.
> http://ftp.tiaonline.org/TR-8/APIC/FSITG/CAPPTG%20(06-08-004)_TIA%20102%5B1%5D.CABC-A(draft).doc
>
> 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.

Agree.  In the open source voice community, many times I see people try to cram 
something into software, even though
they know it's would barely fit or likely would not.  In some of the more 
flagrant cases I've seen, after spending
great time and effort, the end result is poor voice quality (usually due to 
increased latency), unstable system that
crashes or hangs easily, and code that is dependent on server characteristics.  
They're so determined to avoid a
hardware solution they end up with no solution.

-Jeff