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Hardware Support Discussions related to using various hardware setups with SageTV products. Anything relating to capture cards, remotes, infrared receivers/transmitters, system compatibility or other hardware related problems or suggestions should be posted here.

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Old 05-23-2010, 05:39 PM
sagenewbie sagenewbie is offline
Sage User
Join Date: May 2006
Posts: 6
How to: Change channels directly on Comcast DTA

Hi all,

Like so many of us, I was forced to use the comcast DTA boxes when they recently ceased broadcasting most of their channels in the clear over QAM in my area. In my case, I’m running two Hauppauge 1600 cards, and so used a splitter to feed two DTA boxes to the analogue jacks on the 1600s, while also keeping the two QAM jacks on the 1600 connected to the raw cable feeds (for HD locals).

I will say that the quality of the DTA feeds is acceptable, though not as good as what I previously could tune over QAM. I did find that just a bit of tinkering with the contrast and brightness settings for the Hauppauge cards (through the tuner settings in SAGE) helped with the clarity of the picture, but everything still has just a tiny gaussian blur to it. Afraid that’s the best it will get. People with higher end desires and the money to pay for them will need to go the HDPVR route I guess.

Anyhow, the main point of this post is to note that you can directly control the DTA boxes for channel changes without having to use blaster / receiver cables between your computer and the DTAs. Handily, these DTA’s (and I think this is true of all models, whether Motorola / PACE or Thomson) have a female 1/8th inch jack on the back which is meant to allow you to attach an external IR receiver (which also ships with these units). What most folks have done is used Sage to send channel changes to an IR blaster cable, and controlled the DTAs that way. Though that does work, I wanted something more reliable and direct for my Thomson DTA.

If you want to go this route, the first thing to note is that while Hauppauge cards do generally support IR blasters, they seem incapable of emulating the codes for the DTA boxes (and are limited to controlling only one set top box in a multi-tuner system anyhow). I tried and tried to find a workaround to no avail and I suspect other tuner cards will have the same problems. So you’ll need a USB-UIRT. Sage sells them, as do others on the net. This great little box (read more about it in the forums) can learn the codes from the comcast remote control that came with your DTA and emulate them just fine for channel changes. Handily, on the back of the USB-UIRT is also a female 1/8th inch stereo jack which is meant to feed up to two IR blaster cables (one on the “left” pole of the jack, the other on the “right”, and a common ground).

Now wouldn’t it be great if you could just hook up the blaster jack out from the USB-UIRT directly to the IR receiver jack in on the DTA, and obviate all that blinky-flashy IR stuff in the middle? If so, you’d have the equivalent of a serial connection between sage and the DTA. Well, you *can* do this! The trick is that you need a special little optical resistor thingamajig hard wired between the two.

I wondered if anyone had created such a connecting cable – and sure enough, found a great guy on ebay who was selling just such a cable for comcast victims who use slingboxes and tivos. I sent him the specs on the USB-UIRT and he turned around and made me exactly the connecting cables I needed. Please note I am not him, and I am only posting this to repay the extra time he spent with me to create a solution. They work like a charm, and now that I’ve got it all set up, my channel changes are *rock solid*.

So if this sounds like something worth trying to you, here’s what you’ll need:


2) A 1/8th stereo to dual mono 1/8th splitter cable. This is necessary to separate the two feeds available at the back of the USB-UIRT. Such a cable is available here:

Scroll to nearish the bottom of the page. You want: “Stereo Mini Plug Y'd to Left and Right Mono Mini Jacks (all 3.5mm or 1/8")”

3) One (or two, depending on the number of DTAs you want to control) special IR patch cables. These are available from Gary Gray on EBAY, here:

Place an order for the slingbox to Comcast DTA cable. When you place your order, tell him you are actually using a USB-UIRT to control a Comcast DTA box. Specify that the USB-UIRT side of the cable needs a 1/8th inch mono jack, and that the DTA side needs a stereo 1/8th inch jack. He’s now familiar with this.


Read these posts for some general orientation:

My thanks to the authors of those posts! A couple further notes. I found that the .ir files they kindly provided did not work for me – probably because there are subtle differences from one DTA to the next. Here’s an outline of what worked for me:

1) Shut down sage and service. Install drivers for USB-UIRT before plugging it in.

2) If your sage rig currently has any channel remaps (whether for QAM or otherwise), you may need to clear these from your properties file before proceeding. If you find that the USB-UIRT is changing the channels, but seems to do so in an utterly random fashion, previous channel remaps are likely the culprit. I also think it advisable to remove *all* current tuners in “set-up video sources” before proceeding. But you can skip these steps and see if you get lucky first. If not, come back here and start over.

3) Plug in USB-UIRT and start sage. Add a new source (external set top box, channel 3) and proceed as directed in the posts above. After telling Sage you’ll be using the USB-UIRT, you should land at a screen which asks you to name the device (call it something like comcastDTA1). Then you’ll be prompted to point your comcast remote directly at the USB-UIRT and one by one, to push the zero – nine buttons. Do this, and finish setting up the cable line up of your choice.

4) Once finished with the source setup, go to the program guide in Sage and test whether the UIRT is now able to use its onboard IR emitter to change the channels on the DTA. Do so by pointing the front face of the UIRT at the IR receiver provided with the DTA. Run through all of the channels in sage. If every channel changes, you are set to go on to the next step. If you are getting utterly random channel changes, go back to step 2. On the other hand, if you are getting some channels right some of the time, you more likely to need to change the timing and repeat count settings in the IR text file. Using notepad, open: Sagetv/common/remotecodes/USB-UIRTtranceiver/(the device name you assigned, like Replace the single opening line with the following two lines:

(your device name followed by a single space) 0 0 0 500 3000 Enter
RepeatCount 2

The next line under RepeatCount2 should be a long string of IR codes for each channel digit – leave these alone, they are the codes the USB-UIRT learned from the comcast remote. Remember to save the file in notepad. Restart sage and see if channel changes are now working. If not, remove the source and try re-learning the codes. You can also try out different settings for timings and repeat codes in the sage interface, but the ones I provided above have worked for several of us.

5) As of now, the USB-UIRT should be sending the correct IR codes via the emitter on its front panel. We need to redirect those codes to the jack on the back of the USB-UIRT. To do so, open up the working .ir code file as you did in notepad in step 4. Here’s what my file looks like before and after being modified to use the back jack:


comcastDTA1 0 0 0 500 3000 Enter
RepeatCount 2
0 0000 0069 0000 0024…
1 0000 0069 0000 0024…
2 0000 006A 0000 0024…
…Continues for each channel number to 9.

Becomes this:

comcastDTA1_Zone1 0 0 0 500 3000 Enter
RepeatCount 2
0 Z10000 0069 0000 0024…
1 Z10000 0069 0000 0024…
2 Z10000 006A 0000 0024…
…Continues for each channel number to 9.

Note the addition of “underscore Zone1 ” to the device name. And note the addition of “ (space) Z1” after every channel number and directly preceding the actual codes.

Save the new version of the .ir file and restart sage. A handy test of your work is to insert a pair of earbuds into the 1/8th jack on the back of the USB-UIRT. Change channels a couple times, and each time you should hear a loud tone coming from one of the earbuds. If so, you are almost done!

6) Insert the 1/8th stereo to mono splitter cable into the jack on the back of the USB-UIRT. Use your earbuds again to verify which side the signal is being output to. Now connect the mono end of the special cable from Gary to the side carrying the signal. Connect the stereo end to the DTA. And voila!

7) (optional) You can configure a second tuner and DTA by following these instructions again. Make sure to give the second IR device a unique name (e.g. ComcastDTA2) and this will create a separate IR file for your second DTA box. When you get to step 5, use “_Zone2” and “ Z2” when you edit the files. The signal will then appear on the second mono jack of the stereo splitter cable.

Others more experienced than I may have simpler or more direct ways of getting this all up and running – if so, please add your notes to this thread and help me to pay it forward.

Good luck, and thanks to all involved in helping me solve this!

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change channel, comcast, dta, usb-uirt

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