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Published: 2007-06-09 - 21:58:00
Home Theater : Ask The Expert

Why Does My Cable Box Hate Me? It Turns All My HDTV into 480i SD!

By Chris Boylan

Question:

Hello, Big Picture Big Sound,

I am totally new to all things digital. Just this week I installed a home theater system consisting of a Vizio 50-inch Plasma TV, Onkyo HT-S907 receiver and DVD, and an Optimum/Cablevision (Suffolk county, NY) Scientific Atlanta 8330 HD dvr cablebox.

The Problem: the cable box reverts to 480i so that I usually end up watching TV at this resolution. A hard reset of the box restores the HD signal but it usually reverts to SD (standard definition). I have spoken to Cablevision numerous times as well as to Onkyo and Vizio tech support. Each one generally blames the other. The recommendations variously obtained include, getting a new dvr box, going back to a standard (non-dvr) box, turning the system on in a particular sequence (ie tv-receiver-cablebox), configuring the cablebox for only 1080i signal or only 720p which is the Vizio tv resolution.

Any help, advice or direction to web references would be appreciated!

P.S. Composing this e-mail helped to understand the problem better for me, as I didn't know anything about this stuff before a day ago. I guess that's something.

Joe P., Long Island, NY



Answer:

Hi, Joe,

Welcome to the sometimes mystifying world of home theater electronics! For a "newbie," you're doing pretty well so far: you bought some nice gear and are definitely asking the right questions. It sounds like your cable box is trying to detect the resolution capabilities of your system and failing, either due to the Onkyo receiver or Vizio TV giving "bad" information in the HDMI handshake, or (as some have suggested) due to the full signal chain not being completely powered up, which may be necessary in order to deliver proper resolution information back to the source.

There are a few things that should make this problem go away, some of which have been suggested already and some of which have not. I'm assuming you've at least tried a new DVR box to make sure this is not a defect in the box itself (a fairly easy test).

Assuming the behavior persists with a new box, then here are a few suggestions:

  • Power-Up from Display to Source: if you power up the components in the chain starting with the display (Vizio TV), followed by the switcher (Onkyo receiver) followed by the source device (cable box), then the Scientific Atlanta cable box should get accurate information as to the display capabilities of the Vizio TV and should not revert to SD output (480i/p). Purchasing a universal remote such as a Logitech Harmony 880 or Harmony 890 would make this simple as you could just hit one button (e.g., "Watch HDTV") and the remote would power everything on in the proper order, every time. You might want to build in a second or two delay between the power commands being sent to the various components just to make sure they're fully on before the cable box is powered up.


  • Use Component Video output from your cable box instead of DVI or HDMI: HDMI (as well as its video-only sibling DVI) is a two-way connection that can both send and receive information. Component video goes in one direction only - from source to display. With a component video connection, the cable box, if configured correctly, should send the highest quality signal available out to your TV, depending on what you have set in the cable's set-up menu. If you have told the box that your TV supports 1080i, 720p and 480i/p, then the box should set its output resolution to the native resolution of the channel you're watching, and your TV should have no trouble locking to the appropriate signal.

    With high quality component video cables (and with these specific home theater components), you'd be hard-pressed to tell the difference in video quality between HDMI and component video. Also, component video does support the highest output signal of your cable box (1080i). The main drawback to this approach is that you'll need to either plug the component video cable directly into your TV, or, if you wish to route it through your receiver, then you may need to also hook up a component video cable from the Onkyo receiver to the Vizio TV. Some of the Onkyo receiver models support transcoding of the video signal from component video to HDMI, but I do not believe that your specific receiver supports this. You will also need to hook up an audio connection from cable box to receiver (preferably fiber-optic or coax digital) so that you can continue to get discrete surround sound from programs that include Dolby Digital 5.1 sound. So the connections will be more complex, but again, a good quality universal remote control will make this complexity completely transparent to the end user (even mother-in-laws).

    At some point in the future, it's possible that cable and broadcast providers could step down HD broadcasts (1080i/720p) to SD (480i/p) automatically over component video, activating something called the ICT (image constraint token). This is a feature of HDCP (High-Bandwidth Digital Content Protection) that allows content providers to step down the resolution of high definition signals sent over analog transmission lines (e.g., component video). If this happens, then the full resolution high definition signal will only be available over an HDCP-compliant DVI or HDMI connection. This is not an issue yet, but might be some day.


  • Set the Cable Box to 1080i only: If you tell your cable box that your set only supports 1080i, then it should prevent the box from querying the display device, and it should pass-through or up-convert everything to 1080i. You mention that your set's native resolution is 720p, but that's not precisely true - it's actually capable of slightly better resolution (more detail) than 720p. Your Vizio plasma HDTV's native panel resolution is actually 1366x768 pixels, not the 1280x720 pixels that would quality as "720p." What this means is that the set's internal scaler has to convert the signal either way - either it down-converts and de-interlaces 1920x1080 pixels (interlaced) to 1366x768 pixels, or it upconverts 1280x720 pixels up to the standard resolution of the panel, which means it has to generate additional detail that is not in the source signal (48 extra lines). Personally, I'd rather start with more detail (1080i), instead of less detail (720p), so if you choose this approach, then set the box to output 1080i only.

    But, of course, setting your cable box to 1080i-only means that channels like Fox-HD (720p) will actually be upconverted and interlaced by the box to 1080i, then down-converted and de-interlaced by the TV to the native resolution of the panel. But there's nothing good on Fox anyway, except the fake news (entertaining, but is it news?), and Major League Baseball... Oh, and maybe "24" is fun to watch and some people seem to like that crazy "American Idol" show, but I digress...


  • Throw Away Your Cable Box: depending on which Vizio model you have, there should be a built-in digital tuner (ATSC and/or QAM digital cable). With the QAM tuner, you can plug your Cablevision cable directly into the Vizio's coax cable input, select "auto-tune" or "auto-add" and the TV will search through the available cable channels, adding everything it can find, including many if not most of your HD channels (the unencrypted ones anyway). Then you can use the TV's remote to change channels. Yes, you'd lose your PVR functionality, but you'd also simplify your life a bit.

    If you want to simplify your life even more then cut your cable entirely and stick a standard UHF antenna on your roof, point it due West and get all the FREE High Definition channels available from the Empire State Building just a few short miles away. I'm actually in Astoria (Queens) and my little roof antenna pulls in CBS-HD, NBC-HD, Fox-HD, PBS-HD, PBS-Kids, UPN-HD, WB, Qubo, "The Tube" and many additional digital channels without the pleasure of a monthly bill. Radical, I know, but it works for me.

Of the above choices, the "best" option (least disruptive to your life) is probably just training yourself to power up the components in the "proper" order, or training a universal remote to do it for you. And if this solves the problem, then you can settle in and get back to what's really important: Enjoying that Big Picture Big Sound experience!

Regards,

-Chris

Keep those cards and letters coming! if you have a question for one of our home theater experts, shoot us an e-mail to "Ask The Expert." We'll select among these for future installments in this column. Due to the volume of requests we receive, we cannot reply to each question personally.

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