Test Drive: ISDN Replacements - ipDTL

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by Steve Cunningham

Recently I said my final goodbyes to my ISDN phone lines. I know, I was late to the party getting them in the first place, and am now late in losing them. I'd originally had them installed back in the mid-late 1990's, when the monthly cost was about $35 a month to maintain the basic service, and did not include per minute charges. And that was a bargain, both then and now, since many ISDN plans have recently seen their fixed cost-per-month, to simply maintain the service, shoot up from that $30-something per month range, up to the $400 per month seen recently by some Chicago-based VO talent, in a matter of a few months while working under the ISDN yoke of Verizon.

But wait -- why would ISDN rates spike like that in the Chicago market, or elsewhere? Vendors will often raise rates on a scarce product simply because they can, even when the market size is small. One might be tempted to believe that ISDN was so well-liked by the small market of VO that use it, that the phone companies could afford to squeeze more profit from that monthly fee for just having the service. Since those VO folks need that service, their market will likely just remain compliant, accept the increase, and deal with it.

Or perhaps there is another reason for the spike in the pricing of ISDN service. Maybe the phone companies simply want to price ISDN out of existence. True, the market for it consists of profitable businesses, but they tend to be small and their numbers are not increasing. Paying to support these customers is expensive, and wouldn't that time and money be better spent promoting more cell phone services? Why should they keep ISDN around for a shrinking number of businesses? In either case, it would appear that ISDN's days are numbered, whatever the reason, as more reports of price increases appear.

Fortunately, the market is already providing what appear to be suitable replacements for the venerable remote recording technology. This month, let's take a look at one of the newer entries coming to us from out of the UK: ipDTL.


Kevin Leach, a sound engineer for the likes of the BBC and other stations in the UK, had often utilized Skype as a medium for conducting remote broadcasts and interviews for radio. Like most, he found it an effective tool, but the results were variable, due in part to the way Skype interfaced with personal computer's sound facilities and attempted feedback management. Leach's understanding of Skype's VOIP shortcomings lead him to create the initial version of what would become ipDTL product. It eliminated the feedback management portion of Skype and took advantage of Google Chrome's extensive real time communications suite, resulting in the formation of a company known as In:Quality, and a product known as ipDTL.

First things first: ipDTL stands for "Internet Protocol Down The Line," although recently at least here in the US, VO users have tended to refer to the product as "Ip-Dittle." This moniker may or may not catch on as the products' spoken name on this side of the pond, but a note from this author to Kevin Leach, the founder of the company: You might want to manage that pronunciation, my friend.

More important than the pronunciation of the name is how ipDTL works, and how few resources it requires. ipDTL literally requires the following: a reasonably fast internet connection, a computer running the Chrome browser, and a microphone. Oh, and a subscription to use the ipDTL software.

That's it, really. Computer, connection, Chrome, microphone, subscription. The computer can be running just about anything, so long as the Chrome browser is supported. That means Windows XP SP2 or better, Vista, and Win 7 or 8. On the Mac side it's 10.6 or higher, and almost any recent Linux distro will work (Ubuntu 12.4, for example).

What is the definition of a "reasonably fast" internet connection? Not as high as you might think. ipDTL claims the service works with as little as 300kbp/s upload speed, which is quite do-able for even most consumer-grade internet connections. Frankly, my consumer Time Warner Cable Standard connection does over three times that speed on upload, and worked quite well in testing.


Creating a signup on the ipDTL.com page is about as simple as one could want. Figuring out which license you actually need is a bit more complicated at first glance. The first thing one has to remember is that our friend Mr. Leach comes from a radio background (as opposed to a primarily commercial VO background). When he imagined who might be an appropriate customer for ipDTL, his first thought was to a radio station or a radio network. Such a network might buy a full yearly license so it could receive ipDTL sessions and record them, and also one or more limited yearly licenses so that staff field reporters could, one at a time, log in to the station from the field and deliver a report remotely, without having to buy another full yearly license for the privilege. Moreover, a radio station might well be happy with recording remotes at a lesser bandwidth than one would want for recording an ISDN-quality commercial spot.

Thus, there are two groups of yearly licenses available; Standard Audio and HQ Audio. Standard Audio can record at up to 72kbit/sec, while HQ Audio extends the bitrate to 128kbit/sec. More on the actual codec used below, but for purposes of deciding which Audio class to buy, suffice it to say that the vast majority of voice actors rightly opt for the HQ Audio license, which easily duplicates the quality of ISDN's two 64-bit B-channels (and in fact is better than that, better than G.722, in my A/B testing experience between ISDN and ipDTL). The Full license at HQ Audio is $25 per month or $160 per year. The same license at Standard Audio quality is $15 per month or $80 per year. (Note: see ipDTL's website for pound sterling and Euro pricing).

Within the two groups of licenses relative to bitrate, there are multiple categories as well. In both Standard and HQ, one can buy a "Full" license, which permits one to connect to any other user who has ipDTL and a valid license. In both, there is also a "Link +" license, which allows one to send a link to someone who does NOT have an ipDTL license, whether for sourcing or recording, so that individual can work with the Full license owner on a one-off basis. In essence, the "Link +" license is valid for one user, one time, but is infinitely renewable, and is priced the same as is the Full license at either Audio quality. Finally, within the Standard Audio category only, is the aforementioned Limited license, which allows for example a radio field reporter to remotely login and record on the station's computer and Full license, without buying another Full License. The Limited license is $10 per month or $20 per year. Remember that the Limited license can only be used with someone who holds a valid Full license.

To simplify a bit, if you are a voice actor then you will definitely want a Full ipDTL HQ Audio license, which will allow you to voice any session with a client who has its own ipDTL Full license. If, as a voice actor, you would also like to be able to work with clients who don't have their own ipDTL license, then you will want to also buy a Link + license so you can send a web link to those clients.


My favorite part of writing these reviews is telling you what I think about the product, where it works and (more importantly) where it doesn't work.

This time I don't have much to say that hasn't already been said by others. Consider that most voice actors (many of whom I know personally) who have used ipDTL in a working situation have come back with little save rave reviews. Occasionally I've seen a comment that there was a hiccup, but usually under strained circumstances. And I'm sorry, but the very best WiFi networks are almost as good as a wire, so any system that performs well using wireless internet gets an automatic pass from me. And ipDTL does well with wireless networks.

Look, my experience has been extremely good. It sounds good, it's easy to set up, I'm a Google Chrome browser user anyway, so I have no complaints with that. It just works, and it's arrived just in time, given that I finally let go of my ISDN account (and like everything I've let go of, it has claw marks in it).

The main problem with ipDTL right now is lack of adoption. Where voice actors have been willing to push the issue and ask their client to try out ipDTL, and having that extra license helps here, everyone seems to come away happy. So far I have not heard anyone complain about performance or sound quality or reliability. Have there been some hiccups? Yes, but very few. Meanwhile, how many actors are giving up their ISDN, before their telco company raises the rates to untenable levels? More than you might imagine.

So in reality, the only way ipDTL is going to make it is for the VO community to continue to push it forward, little by little. Go try it for yourself, and let me know what you think. I'm in.


One of the more interesting aspects of ipDTL is how it creates what's known as a peer-to-peer connection between the source computer and the recording computer. This type of connection is unique in that it finds a way to get through the firewalls that invariably exist on both ends of a Voice Over IP (VOIP) connection.

In an ideal world, your computer (the source, with your microphone attached as its input) would be able to talk over the internet directly to the computer that was to record that microphone signal. To accomplish this, your computer establishes a connection with the recording computer using TCP (Transfer Control Protocol) packets, which contain all the necessary setup information both computers require to create a bi-directional multiple-handshake connection with each other. Communication using TCP packets requires that each packet sent is acknowledged by the receiver, to ensure that the connection is both fast and secure, which of course slows down the initial communication between the two computers. However, once that connection is completed, your computer switches to sending the far simpler UDP (User Datagram Protocol) packets, which require no such acknowledgement from the receiver and thus can be sent and received far more quickly than can the TCP packets. The conversation between the sender and receiver continues to occur quickly using UDP packets, with TCP packets sent only occasionally to monitor the continuity of the connection. If and when the TCP packets are not acknowledged by the receiver, then the source would begin sending the necessary information to restart the conversation with as little packet loss as possible.

Sometimes ipDTL can make a clear peer-to-peer connection between the source computer and the recording computer. When it can do that, it does. When it cannot, well, it goes to plan B. Because unfortunately we don't always live in an ideal world, the internet can be a dangerous place full of bad actors attempting to do bad things to our computers and connections. For safety's sake, our computers run firewalls and obfuscated IP addresses to prevent those bad actors from doing bad things on our machines. However, those firewalls make creating a peer-to-peer connection between our computers more difficult, as they obfuscate and block direct connections between our computers (performing a function called Network Address Translation, or NAT). The methodology for overcoming these little bumps in the road, when they exist, usually involves engaging another server, which connects the source and recording computers to each other by accepting incoming packets from both machines and then routing them.

This is the purpose of servers that Skype uses for everything from routing packets to checking on the "heartbeats" of a communication session. ipDTL performs the same routing and monitoring. Interestingly, Skype uses primarily its users' servers, at least those that have static IP addresses, as "volunteers" to perform these necessary tasks. ipDTL has its own servers in the UK, Europe, and some in the US to perform similar functions. The majority of those servers are in the UK at the moment, but In:Quality promises that new servers are coming online in the US on a regular basis, concurrent with the increase in US users. The more servers available, the quicker and more capable the connections between audio source computers and recording computers, when both are utilizing ipDTL. With the high need to keep computers behind tight firewalls, the need for ipDTL servers to be available to "punch through" firewalls becomes more important than ever for good performance.

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