Venting on the XLR

I love XLRs.
I hate XLRs.

They are universal, robust, and easy to repair. They have obvious gender to indicate direction. They are the only respectable way to provide a pro-grade, balanced audio I/O. They also carry digital audio.

They are also huge. In an age where portable gear is shrinking, it's crazy to dedicate a one inch diameter circular port to a mono audio feed. And requiring a pair for stereo? don't get me started.

Even in studio gear, the demand for back-panel space has grown. Besides the power socket, we need to now provide video monitor, USB, serial and contact closures. Can you imagine what a piece of gear would look like if each of the signals on these connectors took up the space of an XLR?

Why hasn't the broadcast/pro audio industry moved to something with a more reasonable size?

4G LTE in the United States

Spectrum allocation for 4G wireless services in the US is a mess. Here's a short list of the four major wireless providers and the spectrum on which they serve LTE:

Verizon: Their main network is in the 700MHz band (band 13) but for a couple of years they've been offering LTE in some areas on the AWS band (band 4- upload is 1700MHz and download is 2100MHz). They brand this as XLTE, Users with gear that supports both bands may find themselves automatically pushed into the XLTE band due to lower congestion. And while it's currently less crowded, the higher frequencies result in less coverage and building penetration. Verizon is also now overlaying LTE into older 3G spectrum (Band 2, 1900MHz) in some areas.

AT&T is even more of a hodgepodge, since their legacy of buying other cellphone companies results in a patchwork of licensed frequencies. In most areas, you'll be using AWS (Band 4, 1700/2100) or Band 17 (700MHz). In some areas, they've opened up 3G bands to LTE (Band 2, 1900MHz) and in others they've licensed Band 5 (850MHz). To be safe, you'll need a modem or hotspot to cover all of these bands (like the Comrex Connect modem)

Sprint: They suffer from the legacy of introducing 4G service first, but in a non-LTE form that died away quickly. They now offer LTE in this band 41 (2500MHz) but the extremely high frequency leads to coverage difficulty. They've been promoting their "Vision" plan for the last few years which overlays LTE on all their available spectrum (1900MHz Band 2 and 850MHz Band 26) as well as backhaul upgrades, but our experience is still mixed in many areas.

T-Mobile: Their very late LTE deployment results in mostly urban coverage.LTE is provided mostly in the AWS band 4 (1700/2100MHz) but they've been overlaying on their 3G band 2 (1900MHz) and are starting to deploy LTE on Band 12 (700MHz) in some limited areas where they have spectrum.

So depending on your carrier or location, you may be experiencing LTE on Band 2, 4, 5, 12, 13, 17, 26, or 41. Compare this with most countries that have two choices for all carriers. The situation in the US has resulted in the inability to move a data modem or phone from one carrier to the other. Thankfully, higher-end smartphones and tablets now cover the majority of US bands, so they are portable.

Comrex Connect LTE Modems

USB modems are by far the simplest way to do audio and video remotes over LTE. But they are becoming less available, and their form factor generally isn't "pro-grade". So we're introducing our solution, the Comrex Connect Modem.

There are actually three versions, thanks to all the intricacies (both technical and political) of interworking with multiple LTE providers. One version works on Verizon, one on AT&T, and the other on most non-US networks.

Connects come with nifty mounting solutions designed for our LiveShot and ACCESS portable codecs. They have high-gain adjustable antennae to help in fringe areas. Just add a full-size, subscribed SIM and you're ready to go. Contact your friendly dealer or Comrex sales at sales@comrex.com for more info.

Introducing Fleet Commander

Do you have a "farm" of Comrex audio IP codecs? Do you want a slick, unified interface where you can control all of them? Fleet Commander is that. It's a new Windows application that offers full configuration and control of up to (tbd)* codecs simultaneously.

Fleet Commander also has some unique functions, like the ability to copy custom connections and profiles between codecs.

Fleet Commander has a cost, but we're offering a limited number of free licenses to beta testers. You'll need to qualify as a beta tester by having over three ACCESS or BRIC-Link codecs, and a need to use a unified control app. In other words, we want beta testers who need, will use and provide feedback on Fleet Commander. Drop a note to techies@comrex.com to see if you qualify.
* unlimited based on your computer and network

ACCESS/BRIC-Link 4.0 beta testing

If you're a "cutting edge" type of audio IP codec user, you can now give our 4.0 firmware a spin. It includes the CrossLock VPN reliability layer, which enables the use of multiple networks on a single codec. It also includes support for the U620L modem from Verizon.

4.0 works on all ACCESS Racks, BRIC-Links, and BRIC-Link IIs. It also works on most ACCESS Portable 2USB modems (without the card slot) but you'll need to check with Comrex support to make sure your hardware qualifies.

Verizon's new 4G modem

The modem situation on Verizon's 4G network has not been pretty for the last months. But Big Red has finally introduced a new 4G modem that covers their entire spectrum, deployed and "yet-to-be". It's the U620L and it replaces the "a lot to be desired" 551L modem. It came out in mid-July and we've already integrated support in our ACCESS and LiveShot firmware. LiveShot beta firmware is available now, and ACCESS support is coming in 4.0

Allow me a line or two to whine about USB modems. This is Verizon's fourth-gen 4G modem. So far each modem has used an entirely different software interface, (requiring a firmware update)and a different SIM card size (the U620L uses the Apple-style nano SIM).

Keep making it easy on us Verizon, we love you!

CrossLock is coming to ACCESS/BRIC-Link

We'll be cutting a beta-level release of new audio codec firmware in a couple of weeks.  It will be all about reliability.

As you many have noticed, we've been toiling hard the last few years in the video segment.  It's a lot harder to move video over 3G/4G networks than audio, since it's 10-20 times the digital bandwidth for HD video. So this required that we take a look at how we can stabilize a poor data channel even further. It also required the ability to aggregate multiple IP networks for increased bandwidth.

What we came up with for video was coined "CrossLock". Essentially it's entirely new VPN layer that gets established between your hardware devices. It has all new error correction facilities (including both FEC and ARQ styles) throttling, and the ability to use multiple networks on each end of the link. It's the "killer app" for IP reliability and it's time to deliver it to audio codec users in firmware 4.0

Watch this space for firmware 4.0 release before Sept 1.

Are Robo-calls tying up your IP codecs?

Many ACCESS and BRIC-Link users set their codecs to accept incoming SIP calls, which is required for the the system to be compatible with apps like LinPhone and WebRTC. But a side effect of opening these ports is that they will also answer calls from other SIP-based sources.

We are finding an increasing number of SIP-based "probes" or robo-callers, attempting to make connections with random IP addresses. When one of these hits your codec, it will attempt to answer the call. This typically results in a "hang" condition of the codec until the bad-call timer runs out, defaulted at 60 seconds. This is annoying but not usually a major concern.

Until recently, when we've started seeing a persistence of these dialers to hang on to a codec. When the codec disconnects, the dialer reconnects, resulting in a Denial-of-Service like condition. The user generally needs to reboot his system (maybe a couple of times) for the call to completely clear.

So we took a look at the incoming parameters of these calls to see if there was some way to reject them out-of-hand. And we found a series of "user agents" (the name of the software used to make the call) that were common among these calls.

We now have a beta-level version of firmware for ACCESS and BRIC-Link that adds a "blacklist" which defaults to the three most common user agents we have found in these dialers.  The list can be expanded by the user. If you're experiencing incoming SIP calls on your codecs that tie up your system, ask our support department about an upgrade.  You can reach them at techies@comrex.com.

Edit 3/17/15: Firmware 3.0p6, available at our support page for all models, has this fix. And our UML295s are in stock.

USB modem situation worsens on Verizon

It seems LTE USB modems are going the way of the Dodo bird and ISDN lines fast.  Verizon recently killed off it's line of Pantech modems, and the remaining one, the Novatel USB551L has a lot to be desired (see reviews from the Verizon site on left).

This is even more so on versions recently purchased from Verizon. We got some troubling reports, and got our hands on a sample.  This modem works fine on a computer, but there's a fundamental hardware timing issue that makes it unable to associate with our ACCESS codecs. It doesn't look like there's any work-around, either. So don't buy these.

We will be announcing a long-term solution to the USB modem issue next month at NAB. Until that solution is in place, we'll be stocking the Pantech UML295 (yes, we got a hold of a limited supply) for sale. This is the only USB modem that can take advantage of all of Verizon's LTE bands. And is hands down the best USB solution we have seen so far. Contact our sales department for more info.

Oh and don't forget the idea of using the ACCESS Wifi modem in conjunction with a hotspot device on Verizon! This lets you share your 4G with a computer in the field.

AT&T Please fix tower 15932433

We spend a lot of time testing codec performance on real-life 4G networks. We've found several spots in cities that function well as worst-case scenarios, including the vicinity of the White House and Times Square. We've also found a good testing ground closer to home--the Boston Common. It's a wide open spot in the center of the city where you can count on changing cell towers pretty regularly as you walk around.

We had some interesting results yesterday while testing our LiveShot video codec there. We had three modems attached. (for you audio codec users, this capability is coming soon in firmware 4.0) Verizon and Sprint modems were champs, but depending on location our AT&T modem would behave miserably--to the point where it's presence was actually more of a hindrance to the overall stream than a help.

That was actually good news, since we were trying to tweak our algorithms to minimize or quarantine the data from a bad network. But we took it a bit further and started reading the stats on the modem as it entered and exited the "zone of doom". Sure enough, it was a discrete tower switch at the exact moment the channel fell apart.

The above graph illustrates the percentage of packet loss over time in one second intervals. When viewed on the product, this graph moves in real-time from right (most recent) to left (60 seconds ago). It's pretty obvious when you're on the bad tower.

Why is this particular cell so bad?  Is it located in a place where multipath is a problem on the Common? Is there a local transmitter with a spur in the 700MHz region blanking the cell tower receiver? I'm sure bribing an AT&T tech would be the only answer, and none were around.

In case you think this problem is specific to AT&T, we were at this exact location about 10 months ago, and AT&T was flawless throughout the area. But at that time, an identical situation occurred on Verizon, at the opposite end of the test area. Go figure.

Is POTS dead?

No profound insights or innovative solutions to talk about today. Just a bit of navel-gazing.

We're getting more and more war stories of broadcasters unable to find a "real" POTS line at a venue from which they need to broadcast. The phone jacks they used to rely on get terminated in a VoIP switch. POTS codecs rely on a very intricate modem balance on a phone line. And VoIP systems treat modems like a weed on a putting green-- A nuisance to be destroyed.

Of course the answer is "Go IP", but that's a pretty cold response to someone who doesn't have the budget for shiny new hardware. And IP codecs are still hot commodities hard to find on Ebay. POTS codecs are relatively easy and cheap to find there (possibly a testament to their demise?)

It's really hard to gauge how rough things really are-- we don't hear about the successes as often as the failures. But at a minimum it seems those who show up assuming that RJ-11 is connected to the CO by a pair of copper wires will be disappointed in short order.

I turned off my HD Radio today

I have always had an overall love of broadcasting and care a lot about radio, even in the sectors that don't affect Comrex directly. When the industry finally settled on HD Radio after what seemed like endless debate, I was very skeptical it would add the kind of value the proponents said it would. But I was willing to be proven wrong on that.

It was time for a new vehicle last summer. Being a frugal Yankee, I lean toward well reviewed but value-oriented cars. But being a techie I tend to upgrade those with some shiny options. It turns out one of those options this time around was HD Radio.

I wasn't surprised, given the dismal results of the HD Radio marketing campaign, that I had to teach the sales rep what it was and that it wasn't satellite. On this radio, HD is a global on/off setting i.e. you can't enable a couple of HD2 channels but disable HD1 switch-over on others.

Having had the family in the car now enough times, I made the decision to turn it off. I live about 30 miles from most of the Boston market's FM transmitters in Needham MA. It was result of two conversations. The first from my teenage son:

Him: Dad, why does the sound of the music keep changing?
Me; It's called HD radio. It's switching from old fashioned radio to digital. But the station set their sound processing so different on each side that it sounds like a different song whenever it switches..
Him: Can you make it stop?

The second was with my teenage daughter, listening to the local NPR affiliate:
Her: Why does the guy keep stuttering?
Me: It's called HD Radio. It's switching from analog to digital. But the station hasn't aligned the two signals in time correctly.
Her: Can you make it stop?

At no time was any advantage to HD noticed by any of my family. And HD2 channels are unlistenable in the suburbs. So I made it stop today.