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Favorite Codec combos on a Comrex Access?

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Hey guys here's a question for you... I've got a week full of remotes from a car wash next week with no connectivity other than a 4g Verizon dongle on my Comrex Access. Any ideas from the crew on best codecs to use?

I currently run a mix of AAC-LD (12k limited) to the station (we're talking voice only here) and Bric-ULB as IFB/Predelay back. Seems to work well (since we have dropouts even on LTE with something like Bric HQ) but delay is around .5-1 seconds. Any better ideas? We're going live so I'll take lack of quality over any spuddering or big delay... Hence the low bitrates.

Appreciate your thoughts!
 
I know you were asking other users, but here's my perspective from Comrex
Nothing's going to beat AAC-ELD in that box. It's by far the best engineered algorithm out there for remotes, with the absolute best balance of bandwidth, quality and delay. On LTE you should easily be able to run it in duplex. Is it possible your 4G modem isn't really finding a 4G signal?

Now that we're shipping AAC modes as standard in all ACCESS, we really only continue to deliver the BRIC-HQ stuff for legacy compatibility. Everyone should be running on the AAC modes.
If you're experiencing .5-1 second delay on LTE, either the LTE coverage in your area is poor, or badly implemented.

Modes like ULB were implemented back in the days when using only a trickle of data improved your odds on wireless. These days, our experience is that dropping from 40 to 15kb/s isn't likely to make much difference on wireless networks. When these networks drop out, they do so pretty completely.
 
Noted. The combo of algorithms I'm using here actually carries over from using our original Access units (we have three originals and one shiny new 2USB) with Sprint PCMCIA cards. It has been my experience that the Sprint network here leaves much to be desired in robustness.

I will definitely try some experimenting in the next week with the 4G on the new 2USB.

Thanks!
 
I thought I'd take this opportunity to elucidate a few general principles that probably apply (Sorry, but I haven't had the opportunity to read the options on the Access so just consider these in a generic sense).

I regularly see people say "it's only voice" when considering codec choice. If you want the voice to sound natural, and if there will be *any* background sound, voice is quite hard to encode (Actually it varies considerably on the speaker. When testing AACplus on the Xport I discovered I have a voice that is very hard to encode).

Therefore the first principle is to lower the compression ration as much as feasible. The strategy most overlook is to reduce audio bandwidth by reducing the codec sample rate. In other words, if you have the option of 10 kHz versus 15 kHz the slight naturalness gained by 15 kHz is probably not worth the increase in coding artifacts, all other things being equal.

The flip side of this coin is that the lower the sample rate, the more delay you will have as the frame rate through the DSP is based on the sample rate.

So, within a particular algorithm these are the biggest tradeoffs.

Of course this post is not arguing against the recommendations of "Comrex," just some food for thought.

Rolf
 
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