In the living room, red, white, and yellow RCA jacks are the universal standard for input. If you've ever hooked up a cable box, a VCR, a DVD player, or any video game console such as an Xbox or PS2, you will find this 30-plus-year-old standard still going strong.
Cars have been equipped with speakers and sound systems since the dawn of AM radio. With the advent of navigation systems and DVD players, most high-end cars have an option for video screens as well--either in the dashboard, or folding down from the ceiling.
Figure 1. A/V inputs (RCA jacks): Wouldn't it be nice if car manufacturers just did the usual and put these jacks in your car?
If you have a factory DVD system in your car, you're probably in luck. Some of these systems include RCA input jacks right on the front of the DVD player, so you can plug in your video game device, digital camera, portable video player, or whatever else you have.
However, the front navigation screen presents more of a problem. Because they don't want to raise the ire of lawmakers, U.S. cars manufacturers don't allow video input to the front screen--even if the car is parked.
Even if you don't need the video, chances are you would like to plug arbitrary devices into your car. Perhaps you need to play cassette tapes but your car only has a CD player. And perhaps you have one of the hundreds of portable music players that isn't an iPod. Well, most of the cars have some way to smuggle sound into the stereo--if you can figure out how.
I'm going to skip the usual cop-out solutions of FM modulators and tape adapters, and point you in the direction of getting a clean audio and video signal into your car.
Figure 2. Fold-out in-dash video screen
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The center controls of a car's audio system are usually called the head unit. Depending on the car, the amplifier will be either inside the head unit, or stashed somewhere else in the car, such as under a seat or in the trunk. But the head unit is the audio hub, and all the audio goes through it first to get out to the speakers.
Depending on the complexity of your factory stereo system, the head unit may be dealing with a half-dozen audio sources or more--AM, FM, satellite radio, CD player, external CD changer, DVD player, hands-free cellular, OnStar, and the navigation system. But for most cars, even the most basic stereo system is designed to connect to an external CD changer.
Figure 3. Auxiliary input box from Peripheral/AAMP
Now, don't even think about some sort of standard interface here. Every different head unit has its own proprietary CD changer interface--sometimes several per carmaker. These head units won't enable the audio input unless they actually sense the presence of a CD changer. But if you do have the CD changer installed in the trunk, you can simply splice in a pair of audio wires and voilà.
I don't know what your time is worth, but for my money there's an easier way. For less than $100, you can buy a plug-and-play version of these gadgets from several manufacturers for almost any car you own. (Since these are some of the same manufacturers that make video adapters, which we'll get into next, I'll list all of them in the Resources section at the end of this article.)
Figure 4. Simple Pioneer (IP-bus) input dongle
Now, there's another way. If you were already planning to upgrade to an aftermarket stereo (such as a Pioneer, Kenwood, Alpine, Sony, or Clarion), most of these units either come with a pair of RCA inputs, or have a simple (but proprietary) dongle for their system that enables the AUX in. (Sometimes you simply have to go through the menus on the head unit and enable it.)
Now, if your CD changer is built into the head unit, you're a bit out of luck because there's no audio wire running to the CD changer in the trunk to splice into.
But there's yet another way to get audio in, which applies to both factory and aftermarket head units. Many of these systems are labeled "XM ready," "Sirius ready," or "satellite ready." This, of course, describes yet another handful of fairly nonstandard interfaces, but the fortunate thing is, if you've upgraded to satellite radio, you may be able to piggyback onto the analog audio wires that bring the satellite radio to the head unit. In fact, if you have an aftermarket satellite-ready radio, you can use the XM Direct interface (from Terk, about $50) and you'll get a happy pair of RCA jacks, and it will work even if you don't buy an XM receiver--the head unit will simply say "no signal" but the audio will come through.
Figure 5. XM Direct units from Pioneer
So, the easiest ways to get audio directly into your head unit are:
Splice into the CD changer audio input, for factory head units
Upgrade to an aftermarket head unit with AUX input
Splice into the audio input on any satellite-ready head unit
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There are numerous reasons why you'd want to use the video screen in your car for something other than navigation. One of the more popular upgrades is to install a rear-view camera lens, so that when you back up, a fish-eye view of the obstacles to your reverse motion show up on the console screen. Another popular, if controversial, use is to play back movies and DVDs, which is generally prohibited while the car is in motion, at least in the United States.
Europe is not so restrictive, so one of the solutions people use for their high-end BMWs and Mercedes vehicles is to buy an import version of the entertainment system and transplant that into their car, which has easily accessible video input options.
But you don't have to start wearing tight shirts and socializing medicine to get video into your head unit. Just as with audio, a number of companies have developed adapters to fill this consumer need for video. Generally, these aftermarket adapters provide several video inputs, allowing you to manually switch between them, and even to automatically trigger an input for a rear-view camera when the vehicle switches into reverse.
Now, if you're looking to connect a car PC to the factory navigation screen in your vehicle, there are a few considerations. Nav screens actually have a higher resolution than your average LCD TV screen--they have to have enough resolution to show street names and roads crisply. However, most adapters assume you're just putting video on the screen, so they only input lower resolution S-Video or composite video.
Video input adapters usually inject your video in the path between the navigation system and the LCD display, allowing you to switch between the two without affecting what the navigation screen is currently showing. This nav-LCD connection can be RGB (fixed frequency, analog), TTL (an older digital connection using a lot of wires), or the more modern LVDS/LDI interface. (The latter two of these are the same interfaces used in laptop LCD screens between the video card and the screen.)
Figure 6. G-Net RGB nav screen video adapter
With a few of the newest LVDS cars and adapters, a high-res VGA signal can be input. But for the bulk of the cars out there, S-Video is the sharpest you can get--which is fine for anything but reading fine text.
Just as in audio, every car has its own proprietary Morex adapter, that is, some collection of multicolored and unlabeled wires, that connects the nav system to the LCD screen. While early adapters required the installer to locate and carefully snip and splice the right wires, the newer adapters have harmless plug-and-play interfaces so you can safely install them, even on a leased vehicle.
(If your car did not come with the factory screen, there are still a number of ways to get a video screen installed into your car. For more information, see Chapter 3 of my book, Car PC Hacks.)
So, the easiest ways to get video into your factory-installed automotive screens are:
If you have a fold-down screen/DVD combination, splice your audio and video in between the DVD player and the screen, or find if there are already AUX in jacks on the DVD player
If you have a factory navigation screen, find an aftermarket adapter that allows you to splice in composite, S-Video, or even VGA video
If you have a foreign vehicle and its European cousin has video input to the NAV screen, buy the Euro-entertainment package and transplant it into your own vehicle
There are only a handful of primary manufacturers in the "12V" accessory market (as they call it.) There are also a large number of one-off products designed and manufactured to solve a specific vehicle and model need, such as "AUX in adapters for late '90s Jettas" or the like.
In addition, in these niche markets, sometimes one manufacturer makes the adapter and a number of other companies buy it and put their sticker on it, but don't actually make it. Some companies will also clone other companies' adapters, selling knock-offs, so the standard make-sure-you-can-return-it-if-anything-goes-wrong consumer advice applies.
Here's a list of audio adapter companies:
And here's a list of video adapter companies:
Damien Stolarz is an inventor who's made different kinds of computers talk to each other for a decade. He co-founded Blue Falcon Networks to architect and develop networking software. In 2002, Damien created Robotarmy, a high-technology consulting firm.
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