Analog Broadcast TV will soon be going away.

Even if you're not concerned about that yet, the upgrade to better (perfect!) picture quality and addition channels is well worth the upgrade.

In my case, the end result was going from 3 watchable over the air channels to 12, which all now have perfect picture and audio quality.

After much research, I decided to use my first of two government coupons on a Zenith DTT900 to use with MythTV.

All the Digital Converter Boxes on the market have some type of problem(s), but the Zenith seemed like the best of the bunch. Based on my usage over the past month, I am very happy with the decision and would recommend this device to anyone.

Here's how to get the Zenith DTT900 working with MythTV using a Serial IR Blaster.

Converter Box Overiew

To get any converter box, digital or otherwise, working with MythTV, a couple things are required:

1. Setup the audio and video out from the converter box so it feeds and capture card such as a PVR-150.
2. Setup an IR (Infra-Red) blaster that will change the channel on the converter box by pretending to be a remote control.

The first issue is addressed fairly easily in mythtv-setup, I won't go into that here.

The second issue, controlling the channel on the converter box is a much harder problem. You need to:

1. Select and Purchase an IR Blaster
2. Configure the IR Blaster so that LIRC can talk to it
3. Configure LIRC so that it can control your Digital Converter Box
4. Create a script so that MythTV can change channels through LIRC
5. Configure MythTV to use the channel change script

Select and Purchase an IR Blaster

1. TV-Tuner tuner cards that include IR Blasters
2. Serial IR Blasters
3. Professional IR Blasters (Like the CommandIR 2)

In this article, Serial IR Blasters are what I will cover, primarily because that is what I have.

TV-Tuner tuner cards that include IR Blasters

You may already have an IR Blaster included with your TV Tuner card. I won't go into that here.

Serial IR Blasters

This is considered the entry level, but "good enough" for many people. These are simple devices you can build yourself or buy pre-made. Serial IR Blasters use signals exiting a serial port to power an IR emitter. Technically, these will work fine for many users in many situations, although it's really a hack. If you are a hobbyist who likes to tinker, or has a low budget, consider this options.

First-hand experience has shown my Serial IR Blaster to mis-fire about 1-2% of the time with my emitter mounted directly over the IR Receiver on my Digital Converter Box...your results may vary.

Professional IR Blasters

Professional IR Blasters are the way to go if serial is either not an option for you, or not reliable. The "hack" of using a serial port signal to directly power an IR emitter is known to not be 100% reliable.

I hope to have an evaluation unit soon from CommandIR* so I can write first hand about such devices.

Configure the IR Blaster to talk to LIRC

I followed the directions to get MythDora working with a serial IR Blaster.

I'm not thrilled with how Serial IR Blasters are configured for LIRC. It certainly is not "end-user" friendly, and I ran into issues from trying to follow a couple other sets of directions (which didn't work) before I found the above thread.

Configure LIRC so that it can control your Digital Converter Box

LIRC needs to know which remote signal(s) to send for any given command. In my case, a lirc configuration file for the Zenith DTT900 didn't exist yet, so I had to create one myself.

Now that I've recorded one, the grunt work of this step is done. You can download the file I created:
Zenith DTT900 LIRC Config

The contents of that file needs to be appended to your /etc/lircd.conf file. you can do this by runnning:

cat DTT900 >> /etc/lircd.conf

Create a script so that MythTV can change channels through LIRC

Create the following script as "/cc.sh". I put it in the root directory, so if/when you have to enter the path using a remote control it's easy to enter. If you are trouble-shooting, you can end up entering and deleting this a few times...when entering text using a remote control, shorter is certainly better.

cc.sh

#!/bin/bash
REMOTE_NAME=DTT900
for digit in $(echo $1 | sed -e 's/./& /g'); do
irsend --device=/dev/lircd1 SEND_ONCE $REMOTE_NAME $digit
sleep 0.4 # note, you may have to tweak the interdigit delay up a bit
done
irsend --device=/dev/lircd1 SEND_ONCE $REMOTE_NAME OK

You can run this script from the command line using:
/cc.sh

So for channel 9, I would enter:
/cc.sh 009

Go ahead and try it. Make sure you can change channels using the script from the command line before you try and get it working through MythTV.

Configure MythTV to use the channel change script

Go into mythtv, watch live tv, and (if needed) change the channel so you can see the video feed from the Digital Converter Box.

Run mythtv-setup, open up the configuration screen for the input "device" you are need to control the set-top box. Set "External channel change command" to "/cc.sh". If you need to set a channel preset (3 or 4), set that here as well.

Try it

Exit mythtv-setup and watch live tv again. When you try and change the channel, mythtv should run the /cc.sh script and change the channel on your Digital Converter Box.

Additional Notes

Depending on if your local stations have sub-channels, you may need to change the frequency number using the channel editor so that it uses the three digit format.

The Zenith DTT900 has a "feature" I wish were not there...
If you are watching, let's say channel 9, a channel with sub-channels. If, using the remote, you enter 9,OK again, it will switch to the second sub-channel.

You can get around this "feature" by sending 009,OK. This becomes a problem when MythTV tries to record two programs in a row on the same channel.

* CommandIR has been an advertiser on MythPVR.com