Batboard

"Beef is Scarcer than Some Lamb!"

http://flattop.its.bldrdoc.gov/spectrum/P25/

Larry

Larry, do you know your site is compromised and is sending out a VIRIS when you connect for the astro samples?

Sockets De Trois Trojan Horse

Since your post, I've tried it on 3 different PCs, two of them running the latest McAfee anti virus, plus a third PC running the Norton current antivirus (all DAT files are current). No problems whatsoever showing at all with thorough scans.

Sounds like you may have something going on with your particualr PC that is manifesting itself when you hit this site. The site appears perfectly clean, including when I open up the WAVs.

Larry

odd, norton firewall says there is something there.

Weird - must be falsing on something

Keep in mind that those WAVs for IMBE quality reside on the U.S. Dept of Commerce NTIA main website. Those folks would not be likely to let some virus sit on their site! Those IMBE Test WAVs have been there for quite some time, and I would guess that the average user opening those WAVs is an engineer/techie type, so if there was a virus, they'd sound off to the NTIA.

Larry

[insidejoke]
What? No "cross-town bus"?! This is an outrage!
[/insidejoke]

Yes, IMBE does some funny things as the bit error rate climbs, but even funnier is to feed IMBE things outside what is was designed for.

I was doing some testing, as for grins decided to feed the opening few bars of Kansas's "Carry On Wayward Son" - which is nothing but multiple vocals.

The poor vocoder really barfed on that - you could understand what was being sung, but it was VERY distorted, since the vocoder doesn't have entries in its code tables for "more than one voice".

It will be interesting to see how the AMBE vocoder performs when they start making that a requirement - AMBE has entries in the codebook for DTMF, sine, and such, so it will do a few things better than IMBE.

Wowbagger wrote:[insidejoke]

It will be interesting to see how the AMBE vocoder performs when they start making that a requirement - AMBE has entries in the codebook for DTMF, sine, and such, so it will do a few things better than IMBE.

Right now, I like IMBE just fine- AMBE will probably be nice too- just as long as it isn't transmitted over an AM carrier, like iDEN....

Also, talking on a CDMA enabled phone, I realized that CDMA audio isn't a whole heck of a lot better sounding than IMBE audio. I guess that perhaps both are FM signals- which may explain something.

-Josh

The modulation format is irrelevant - AM, FM, CQPSK, it really does not matter. All that matters is the bit error rate - for a given BER any IMBE will sound the same.

CDMA phones use VSELP rather than IMBE, if I remember correctly. Different vocoder.

However, you have to remember that in any case, you are trying to squeeze voice down to hundreds of bits per second - in many cases you are compressing the voice to less bits per second than it would take to represent the TEXT of the conversation. You aren't going to get high fidelity out of that.

It's quite interseting to take a visit to DVSI's web site and check out their audio samples of AMBE+2. http://www.dvsinc.com/samples.htm

In my opinion, AMBE+2 sounds every bit as good as IMBE, and actually better, with a much lower vocoder rate. After all, digital is all about squeezing the same, and more, out of less and less bandwidth. You know, just like your boss asks you to do at work---more for less, with fewer people. Just like achieving better gas mileage, with improved 0 - 60 times!

Even IMBE amazes me when I think how crystal clear the recovered audio is over the slow 9600 baud ASTRO modem. I can certainly remember just 15 or so years ago when you certainly could not get great sounding voice recovery with a 9600 baud modem connection! IMBE sounds every bit as good as a typical straight VF analog voice phone connection, and think of the advantages of digitizing it and being able to run it anywhere in the world at 9600 baud, without the losses and analog distortion that results from overseas analog voice phone calls.

Can't wait for the Quantar replacement machine with VoIP!

Larry