How High is Your Definition: A Look at Broadcast Resolutions

HDTV Not all High Definition content is created equal. We all know that an upscaled DVD can’t match the image clarity of a BluRay disc. Definition, also known as resolution, can even change between movies on BluRay format. You should also know that not all television HD content is created equal. Even if the channel your watching is clearQAM and marked “HD” you may still be receiving content on par with regular analog.

Despite the fact that clearQAM signals from your cable company are digital signals that doesn’t mean they are HD quality. A quick check of your area on the SiliconDust website will show you that not all clearQAM channels are even close to true High Definition Resolutions. In fact a quick look at the Columbus, OH area shows that the majority of stations are being sent out at 480i/p, which is basically analog resolution in a digital wrapper.

SIlicon Dust clearQAM Resolutions

To add insult to injury, your cable company’s compression methods can produce image artifacts and other distortions of the original image lessening the image quality even further. Many enthusiasts will be quick to tell you that antenna based digital reception is by far the superior method of bringing HDTV into your home. Content broadcast over the air is uncompressed and so doesn’t include these artifacts and distortions introduces by cable and satellite providers.

HDTV Cable/Satellite Compression

However, not all over the air content is sent out in the highest possible format either. Digital over the air is typically broadcast in either 720p or 1080i. Both formats have their advantages, 720p gives smoother motion packing twice the frames but half the resolution of 1080i which provides twice the pixel at half the frames per second. Typically 720p is the preferred resolution for fast action events such as sports, while 1080i would be preferred for most movie and TV series’.


This is where the problem with how American providers have chosen to implement digital distribution comes in. In the United States providers have chosen to distribute all content in a single resolution instead of choosing the appropriate mode for a particular show. Fox and ABC have chosen 720p while most other networks are broadcasting in 1080i. As a side note, this single resolution ideal is also present on the cable/satellite side of things with a listing of resolutions for each channel found on CNET’s HDTV World page.

So remember that not all digital is created equal and even if it says “HD” it may very well not be a High Definition at all. While over the air is certainly the best method for getting a clear HD signal it has it’s own pitfalls, including being limited to only the local stations. In my opinion, the best way to get all your HD is to try out all the options available to you and select the best combination of methods.

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bjdraw said...

I'd point out that the "real" reason Fox and ABC choose 720p has nothing to do with the fast motion and everything to do with the fact that the bit rate requirements are about 30% lower on 720p60 vs 1080i60.

And before you make the claim both formats use comparable bitrates, without going into keyframes and how mpeg compression works, just take a look at your HDHomeRun gui and you'll see it is less.

MHealy said...

The reason why any given station chose a particular resolution was never discussed in the article. The fact that they chose a singular resolution format over variable resolutions was however. Perhaps you misread.

I see no justification in reduced bit rates either, especially when dealing with ATSC broadcast as opposed to clearQAM, where the same bandwidth restrictions wouldn't apply.

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