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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: Mon, 24 Mar 2008 23:39:32 -0400
User-agent: Thunderbird (X11/20080226)

Gregory Maxwell wrote:
On Mon, Mar 24, 2008 at 11:24 AM, Jeff Brower <address@hidden> wrote:
 > 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.
 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.

You guys do realize that the 'hardware' AMBE solutions are just
software running on a TI DSP, don't you?

That is what I meant by "peeking in the black box". :)
Unlike filters or RF mixers wisely implemented in the analog domain
for reasons of physics, dynamic range, and component availability AMBE
is available only on chips in order to protect the ability of some to
profit at the expense of freedom and flexibility for users of the
technology.  (I'm making no argument here about the ethics of limiting
people's freedom in order to maximize profit, only pointing out the
irrefutable fact it is being done. Being that this is *GNU*Radio
perhaps I should be, however).

Well, after being part of a weird process where my employer had to sign a NDA and get an account to access one small area of a company's site to look at one datasheet for a hardware chip my employer was considering, I think DVSI is reasonable in providing AMBE2000 documentation freely on their website even if it is marked confidential. Hardware companies should be in the business of providing hardware. Some companies feel that hiding how to interface to the hardware gives them a competitive advantage and it seems some companies go to extremes.

I thought about the issues of including IMBE support in GNU Radio but did not think it would spark a lively discussion. I consider the other long-term GNURadio developers like EB to have a better handle on these issues. I just use and write GNURadio code as my hobby of learning about and building SDR. I think it is neat that when I have an interest in some digital mode I can code a receiver and learn some DSP techniques. So if it is decided not to include IMBE support in GNURadio then I will still likely write it for my own private use.

On another note, I found some example ASCP source code for the RF Space SDR-14 that I can modify to use with the DV Dongle. I got off on the wrong foot on DV Dongle list but I got a surprise tonight of the AMBETest application posted to the web site. This is a good start but I may still need to write some of my own code.

If I modify the SDR-14 files to work on the DV Dongle and get a C++ API for my experiments then I plan to feed that back to the DV Dongle project. They need some example files if they expect software developers to use it for other modes.

73 Eric

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