HD 101: IR blasters, HDMI-CEC, RS-232 and IP control
By Ben Drawbaugh 
posted June 30th 2010 11:00AM
posted June 30th 2010 11:00AM
Just getting into HD? Check out these other HD 101 features:
HD 101: Overscan and why all TVs do it
What is ATSC, PSIP, QAM, and 8-VSB?
How to use Dolby TrueHD and DTS-HD with your PS3
Why there are black bars on HDTVs
Infrared (IR)
This is the king of control protocols in the living room and in fact just about every remote control made in recent history uses it to deliver controls from across a room. It's very basic in that the remote emits light at a wavelength outside our eye's range and the receiving device patiently waits for the signal. Because it's based on light its line of sight (i.e. if someone is standing in the way the remote doesn't work). The only wonderful thing about IR though is its universal support, and so it is the de facto control standard. While no control protocol is perfect, the big problem with IR is that most devices can't send signals, only receive them. This means that while you can buy a programmable remote to control everything in your rack, the Blu-ray player can't send a signal to your TV and tell it to turn on. Technically it's possible, but since every manufacturer uses its own IR codes, even if the Blu-ray player did have an emitter, odds are it wouldn't emit the correct signal. Lets assume for a second, though, that every device did use the same codes. Then you'd still have two more problems. Since IR is line of sight any TV in range would respond, and even worse, if something was blocking the signal it wouldn't work at all.
There have been some devices that emit IR signals to control other devices like the original TiVo, the Slingbox and in the near future the Google TV, so to deal with the line of sight issue, IR blasters are used. A blaster is basically an IR emitter attached via a wire directly to the controlled device. This way you can place the emitter directly in front of the device you're controlling in an attempt to ensure nothing gets in the way. IR blasters work pretty good as long as they stay in place -- especially if you install a shield that blocks stray IR signals -- but still don't overcome IR's one way nature. And of course the controlling device must be programmed to send the appropriate IR signals and timings. It also helps if the device support discrete IR codes for on and off, as reliably controlling a device with only toggle power commands can be almost impossible.
High-Definition Multimedia Interface - Consumer Electronics Control (HDMI-CEC)
HDMI has really taken off as the new standard in connectivity in the home theater and for good reason -- it isn't perfect though. Instead of requiring a number of cables to carry the various signals between your Blu-ray player and your HDTV, a single cable carries audio, video and other data like control signals. Unfortunately HDMI-CEC isn't nearly as popular as HDMI, and even when it is supported, manufacturers only support it when connected to the same brand hardware. Most even go further and re-brand it like Samsung who calls it Anynet while Panasonic that calls it VIERA Link. In reality most of the basics do work between different manufacturers and since no programming is required, many functions just work. The best example is when you turn on a Blu-ray player, the HDTV would also turn on and switch to the input that the Blu-ray player is connected to. There are also examples of when it doesn't work, and sometimes it is intentional. We've seen a few devices that would probably work together, but disable themselves if they don't detect the expected device on the other end. But even worse, some manufacturers don't seem to support it at all which can at best be annoying, but at worst prevent other devices from communicating -- for example if you have a Blu-ray player connected to an HDTV via a AVR that doesn't support HDMI-CEC, then it doesn't work at all. We've even seen some HDMI cables that won't pass the signals, so yeah, there's lots that can go wrong here.
All the bad things aside, HDMI-CEC does have the most potential of all the control protocols used in the home theater, but until it is widely supported by the industry, it'll never gain significant traction in the home. When it does work it is pretty sweet, especially since it is truly plug and play -- so no programming required.
RS-232
Oh the interface that'll never die lives on in the our home theaters too. It even uses our old friend the DB-9 connector and is pretty universal. After you get the old 8-N-1 going you'll have to know the codes which can be more difficult to come by since there isn't exactly large databases of codes like there are for IR remotes, and you can't exactly learn the codes either. But when you can get the protocol from the manufacturer you have yourselves some very reliable two-way control. Now of course most devices don't sport RS-232 ports these days and even when they do there's only one. So it isn't like you can daisy chain 'em like HDMI-CEC, which means you need a dedicated device to control everything. This device can be as simple as an old PC loaded with serial ports or as high end as a Crestron controller that retails for more than most cars.
1394 (aka Firewire)
This isn't exactly one of the first things that pop in your head when you think of control interfaces, but anyone who has transferred video from a HDV camcorder knows that you can control the camcorder from the capture software. Well these same controls and more are available to make recording via 1394 from a set-top box possible. And while we've only seen a few HDTVs with 1394 ports, there are lots and lots of cable set-top boxes with them -- although thanks to a loophole in an FCC mandate, many of the ports don't actually work. We've seen people use the 1394 port to change channels on their cable box from their HTPC. It is more reliable than IR, but not nearly as widely supported.
IP control
The most prolific communications protocol in the world is also useful for controlling some home theater gear; and has the best chance of taking over the job of being the de facto standard from IR. More and more devices are internet connected than ever these days and in many cases these same Ethernet ports can be used to control the device. Sadly many of these protocols are not documented at all and only exist to allow the manufacturer's iPhone remote to work. Luckily most of these devices don't require authentication so using a network sniffer to discover the protocol isn't beyond the abilities of any decent networking geek. So far we haven't seen the adoption we need to really make IP the new standard, but there are plenty of AV receivers, and Blu-ray players that can be controlled like this and TiVo's have performed this trick for years. The best part is that most of the IP control protocols we've seen go beyond basic on/off and transport controls and do allow you to query data from the device and other fancy things.
Lots of options, but no silver bullet
As you can see there are plenty of control options for your home theater gear way beyond IR, but even with some very carefully planning you'll probably end up using more than a few of them at the same time. The only two that have any chance of being used by your mom is HDMI-CEC and IP control with the later being a stretch since it requires all the devices be connected to the same network. We say that because both can auto discover and configure themselves once the proper plumbing is in place. But at the risk of sounding like a broken record if just about every device out there doesn't support the same control interface, then it is all for naught.
@kevon27
Yep, and you know what? Fat people still existed in the 80s despite the tremendous exercise that getting up to change the channel provided.
@Pacey Yes, they existed in the 80's but which decade that the most fat people? It's the 90's and 2000's.. all because of the remote.
@kevon27
This isn't just about being lazy. This is about simple things like your Tivo being able to control your cable box. Without this capability, a non-CC Tivo has no way of tuning in scrambled cable channels.
I use the USB ports on the DirecTV receivers for this very thing. Others use firewire ports or IR blasters to change the channel on an STB they are recording from.
In my experience, the USB ports on the DTV recievers are nearly troublesome enough to not be worth bothering with.
@kevon27
I guess you'll need to convince electronics companies to actually put the function button on the TV, receiver, cable box, etc, instead of just on the remote then. Sure, Power is on the TV, but a lot of other functions aren't.
Plus, if you are just talking about turning the equipment off, how much more exercise will you get turning the stuff off by hand, then leaving the room, over just leaving the room after hitting off on the remote?
My Panasonic TC-P42G10 HDTV communicates with my Sony PS3 CECH-2001A (slim 120GB USA) over HDMI-CEC. It does this so well, in fact, that it has eliminated any need or desire I may have had to purchase Sony's bluetooth remote or the PS3 bluetooth adapter for my Harmony remote.
There are only two disadvantages to the setup I'm using:
1) The TV will automatically turn on the PS3 when I switch to the correct input, but the reverse is not true; the TV will not turn OFF the PS3 when I switch AWAY; it'll only switch off the PS3 when the TV is turned off. In addition, the PS3 cannot be switched off using HDMI-CEC if it is playing a disc; it has to be on the XMB. I have to do a bit of a cumbersome dance to power down my PS3 and move on to some other activity. No big deal though.
2) The TV can't send a repeating command. Meaning, if I have to scroll down a long list of items in the XMB, the TV can't send a dooooooooooooooooooooooooooooooooooooooown command so I can't just hold the 'down' button on my remote. I have to keep tapping it, and there is a delay between commands sent to the TV, so I can't tap very quickly. But in those scenarios, I just reach for my PS3 controller.
So yeah, I'm using a combo of HDMI-CEC and a Logitech Harmony remote control.
Well, I'm using RS-232 from my HTPC to turn my TV on and off, IR to control my audio receiver, wifi for my Ipod Touch remote, and 2.4 GHz for my Gyration remote! And strangely enough, since it all goes through the PC, it all works very well together.
Nice article.. I agree BT should have been mentioned, but isn't widely used.. definitely shows they need a standard!
This is why I love EventGhost (http://eventghost.org).. I'm not into Home Theater installation, but you can get it to do anything IR, RS-232, BT, or communicate through the network.. it takes a lot of work to setup, but the plugin system is great, and already supports a lot of hardware..
I created an Android app to communicate with EventGhost.. this is about as close as you can get to controlling everything. You are still relying on devices to have discreet codes, and may still be limited to one-way communication based on your hardware..
Best 101 article yet, keep 'em up Ben.
Awesome post. Can you guys do a post on surround sound and the kind of equipment and connections required for a 5.1/7.1 audio with PS3, Xbox and hd-TVs.
I've been spending a lot on amplifiers and optical cables for getting the surround sound experience with PS3
next, you should do an article on eventghost and writing python scripts to control everything via anything.
For a solution to let the home automation system talk with HDMI CEC devices:
http://www.kwikwai.com/
i know it's not on many devices, but what about RF. Yeah it's about as simple as IR, but at least it gives you non-line of sight functionality.
HDMI -CEC is the work of Satan himself. I setup home theater systems and the like and I shut that crap off every single time. Most hd boxes can and usually are left on. This screws up the entire hdmi cec interaction. Or even better, imagine if you left a disc in your bluray player. You press eject to get it out, and the entire system switches over. If you have a Harmony remote, this can also screw up things with hdmi cec turned on. Bottom line hdmi cec sucks.
That being said, if a viewer only has a tv and bluray, it can make this dead easy, but it's really the only situation that works with hdmi cec.
It ends up costing more to fix one or more of the broken features then just buying a separate component.