Connect a mini to an older RGB-only HDTV

Mar 19, '06 07:30:00AM

Contributed by: robg

Tiger only hintIf you don't check macworld.com on a daily basis, you may not know that I spent the last week writing a very detailed series of articles about the Core Duo mini. I used it in a variety of tasks, from basic word processing through gaming, and basically just wrote about everything I discovered while using it. Overall, I was quite impressed by the newest Intel Mac. There are three parts to the series (linked from the above story), as well as a follow-up to answer some readers' questions.

Some of my testing involved hooking the mini up to our high definition television (HDTV). For those of you with newer HDTV's, this is a simple task, as it apparently just works. But our set, a Pioneer SD-582HD5, is nearly five years old, and lacks any form of computer connectivity other than an RGB input. I spent many hours with Google, talking to friends, and playing with way too much hardware in the family room before I finally got things working acceptably.

So I thought I'd take a few minutes and document what I did here, just in case there are three or four others of you out there, trying to do the same thing (I can't imagine this hint will apply to a large number of readers!). If anyone knows an easier way to do what I just did, I'd love to hear that, too.

(As an aside, if you'd like to see the difference between HD quality and DVD quality, check out this short one-frame comparison movie I made for a Macworld article, using the latest Harry Potter movie and its HD trailer: 836x354, 548KB1673x709, 1.7MB)

Before we begin, keep in mind that you're proceeding at your own risk here :). I don't think it's possible to physically damage an HDTV set with any of this trickery (and I certainly saw a lot of distortion patterns on mine before I got it working) ... but just in case it is, consider yourself forewarned. These steps are also from memory and some rough notes jotted down when in the midst of the process. I think I got it all straightened out in the end, though, but it's possible there are a few minor errors.

Although this is written relative to the mini, this basic process should work just as well for any machine capable of playing back HD video. And again, this is specific to an HDTV with RGB inputs. If you have a new mini and your TV has an HDMI or DVI connection, then it should "just work." Also keep in mind I am far from a video expert, so there are probably technical inaccuracies in the following, but hopefully none that affect the tip's functionality. The tip also assumes you have 10.4; it may be possible using 10.3 as well, but it would require some changes. Finally, this is a very detailed writeup, mainly so that I can easily use it as a reference in the future if need be. I apologize in advance for the verbosity.

Here are some things you'll need to have, or to have done, before you start the actual connection process:

Now the actual connection and configuration begins...
  1. Because of my AirPort connectivity issue at startup, I chose to boot once with the monitor attached, get connected to AirPort, and then sleep the system. If your mini connects automatically, you can skip this step.

  2. Make sure your television is off. Connect the RGB cable between the mini and the television. On our set, this is a switchable input; there's a toggle next to the RGB port that I had to flip over to activate the connection.

  3. From the PowerBook, launch CotVNC and connect to the mini. You should now see the 800x600 screen you set up earlier. From here on, all listed commands, unless specifically called out, are to be executed on the mini via CotVNC.

  4. Open Displays in System Preferences, and see what resolutions are listed. More than likely, and the reason you're reading this hint, is that you won't see anything unique in the list. I don't recall what was listed for me, but I think it was your standard set of resolutions between 640x480 up to 1280x1024. If you're lucky, really lucky, you'll see some interlaced and widescreen options listed (that's what those who connect via DVI/HDMI will see), and you'll be done (pick one and it should work). More than likely, though, you'll see nothing useful.

  5. Now you need to find out what resolutions your HDTV supports. Hopefully this information is in your manual, but if it's not, searching Google with the model number of your set and available resolutions should produce some meaningful matches. In my case, our Pioneer supports 480i, 480p, and 1080i.

    A brief aside on the 'i' and 'p' settings for the above resolutions. The 'i' means interlaced, which means the TV draws every other line on one pass, then goes back on pass two and fills in the missing lines. The 'p' means progressive, which draws every line in order. When used for displaying a computer screen, interlaced pictures are horrendously flickery, but when playing video back, you won't notice the interlacing. So for my TV, a 1080i signal would give me the best HD playback, with a usable but flickery computer screen. 480p, on the other hand, would make a beautifully stable, but quite small, computer screen, and lowered quality for HD video. Since I mainly wanted the mini to play back HD clips, I needed to find a way to send a 1080i signal from the mini.

  6. Enter DisplayConfigX. This program lets you tell the Mac to send any sort of video signal you desire to the attached monitor. It does this by installing customized resolution settings directly into the Displays preferences panel, through a special display Overrides directory. When you register, you can create your own settings from scratch, as well as use some predefined higher-quality settings that might work right out of the box. As noted earlier, you'll need the registered version to make this tip work.

  7. Click on the Resolutions tab, then click the + sign at the lower left to add a new resolution. In the new window that opens, select a resolution that matches one your HDTV offers. In my case, I chose HDTV 1080i. Click the Done button, and you'll see the new resolution at the bottom of the list. Repeat this process for any other resolutions your television offers. (I added 'SDTV-480p' and 'NTSC-480i' to the list.) You can also, if you wish, uncheck any entries in the Resolutions tab that your TV does not offer; this will deactivate those resolutions. I suggest leaving 800x600, or whatever resolution you were currently using, in the list.

  8. Now click on the Install tab, then click the Install button. This will copy your newly-defined resolutions into the Displays Preferences Panel. At this point, take note of the Uninstall button, and the directions underneath, just in case things go horribly wrong.

  9. To see the new values in the Displays panel, you must restart (you can try pressing the Detect Displays button, but I never had any luck with it). After the restart, reconnect via CotVNC on the PowerBook, and open the Displays panel.

  10. Turn on your HDTV; there probably won't be a picture yet, instead you'll just see distortion patterns. On the PowerBook, select one of the HD resolutions you just installed. Your HDTV should now switch over to the new resolution, giving you a picture--and most importantly, the ability to click the confirmation button to retain the new settings. If you're using a high resolution such as 1080i, you may find (as I did) that CotVNC can't refresh quickly enough to show the confirmation button, hence the need to use the mini's mouse to confirm via the HDTV image.
Whew, at this point, you're almost done. What you'll probably find now is that you can't see some/all of the menubar and/or Dock, or perhaps the left and right sides of the screen. This is due to something called overscan, wherein your TV is actually drawing those images off the top and bottom of the display. To fix the problem, you'll need to re-launch DisplayConfigX, and invest a few minutes of your time, along with a few reboots.

In DisplayConfigX, select the resolution you're using (1080i in my case) from the Resolutions tab. With it selected, click the plus sign again. This will bring up the New Resolution screen, with the selected values already completed. Now click the pop-up at the top of the window, and change it to Timing. Every field on the screen is now editable, and you'll want to change the Front porch (top or left border) and Back porch (bottom or right border) settings for the Vertical and/or Horizontal columns as appropriate. To make the menubar and Dock visible, for instance, you need to increase the Front and Back Porch values in the Vertical column. In doing this, you also need to change the Active entry, such that the figure in Total doesn't change. Total is simply Active + Front Porch + Sync + Back Porch. I'll use my settings as an example, and hopefully that will make this bit clearer.

Here are the default settings for 1080i in DisplayConfigX:


When I worked on my overscan settings, after a few iterations (more on that below), here is what I came out with:


As you can see, I had to move the Front Porch from 24 to 62, and the Back Porch from 20 to 122. Since these values increased by a total of 140, that amount had to come out of Active, dropping it from 1080 to 940. These are large overscan values, and there's apparently a service mode hack for our Pioneer that will reduce the overscan. I plan to test that this week sometime, as if I can lower the overscan, I can reduce the porch sizes, giving back more resolution for the picture itself.

So how do you find your ideal porch values? Lots of testing and rebooting, in my case. (You can try to use the Test Screen tab in DisplayConfigX to measure how many lines are missing, but I found it too hard to read on the 1080i screen.) The basic process is: duplicate the basic setup, and tweak the porch values a bit. Click OK to add the resolution, then click the Install tab and then the Install button to put the new resolution in the system. Reboot the mini to enable the new resolution, open the Displays System Preferences panel, and select the new resolution.

Now test the Dock and menubar and see how much of them are visible. If you got things spot-on, congrats, you're done! If, like me, you missed badly the first time, return to DisplayConfigX and repeat the process -- duplicate the resolution you just tested, increase the porch values again (remembering to decrease the Active value by the same amount), save the resolution, install the resolution, reboot, select the resolution, and test. I did three iterations of this before I got the settings basically correct for our set.

Once you've got the Dock and the menubar, you're done. You can try playing some HD videos, and they should look great. Of course, if you haven't bought a 'minijack to Toslink' audio cable, you'll be listening to the crummy Intel mini's speaker, but you're on your own for that one.

If you ever move the mini to another monitor, you (probably) don't need to worry about losing your display settings. DisplayConfigX stores your custom settings as the values for an unknown monitor. I moved the mini back and forth several times, and never lost my custom setups. You could, however, lose your settings if you connect another unkown monitor, as it seems that OS X keeps only one set of settings for any unknown monitor. Note that I do not know this for a fact, but I believe I read it somewhere on the DisplayConfigX website.

I hope this helps the (more than likely) very few of you out there who are interested in connecting your mini (or other HD-capable system) to an older RGB-only HDTV.

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