How we transmit HD signals

Someone over on the Insight forum on Broadband Reports had this question about how we transmit our HD signals:

[CATV] HD resolution I know that networks such as ABC broadcast in 720p and others such as CBS send 1080i. My question is; how does Insight send that signal to us? Do they pass it through or convert everything to 720p? Specifically, I live in the Columbus, Ohio area and have a Motorola DCT6412 III DVR box.

First, a high definition primer

HD signals are not all the same. The numbers (720 and 1080) refer to how many vertical lines are scanned on a television screen. Simply put, more is better because more lines delivers more visual information for our brains to "process" resulting in sharper pictures.

The "i" (interlaced) and "p" (progressive) refer to how the picture is painted onto the screen. Televisions historically have used interlaced painting which delivered every other line in 1/60 of a second and the then fills in the missing lines in the next 1/60 of a second. That happens so fast, the picture looks complete.

Progressive scanning is a more recent technology, first available only in the 720 format. Progressive scanning paints the picture line-by-line, in order. In certain conditions, such as slow motion video pictures, interlaced pictures can have a bit of a combing effect.   More recently 1080 televisions are being made to receive progressive scans.

HD televisions are labeled 720p, 1080i, or 1080p. All of them will accept and display any HD format from a source, such as a television network or a DVD player.  They will, however, convert the signal to the format that the TV is labeled. That means that if you own a 720p HDTV, you can watch your favorite programs that are transmitted in 1080p or 1080i but you will see them in your TV's limited 720p format.

Now, to get back to the answer to the question asked

Insight retransmits the HD signals we receive in the same format in which we receive them. If a broadcaster or cable network is transmitting in 720p, that's what we send out. If we receive the signal in 1080i or 1080p, that's what we send out.

Comments

[cypherstream]

The only problem is the Motorola HD boxes convert everything to one specified resolution set in the obscure (power off, menu) screen. So you can only pick 480i, 480p, 720p, 1080i... not a combination of them. So for instance I have mine set to 1080i, but when I watch stuff like ABC, ESPN, FOX (which natively broadcast in 720p), my picture looks softer and lacking the detail of 1080i. If I power off the box and change the resolution to 720p, then those channels look much sharper, but it throws off the 1080i native channels into a slightly less detail state (NBC, CBS, Discovery, etc..).

I'd like to see MSO's push Motorola as hard as they can to release a firmware update that allows native HD resolution selection, without powering the box off. Sometimes you cannot change the resolution due to a recording in progress on the DVR. This shouldn't be a hard task, Scientific Atlanta, Pace, DirecTV, Dish Network, and Tivo HD all figured this out. Why is Motorola the oddball on this very simple, yet important feature of HD quality viewing.

[sineswiper]

Seems like a better solution would be to make sure that the Motorola version will broadcast in 1080p, not 1080i. If you're converting from 720p to 1080i, it's probably the interlacing conversion that's causing the "less detail" you're seeing. After all, if you have a 1080p HDTV, it's going to upconvert a 720p signal anyway.

Eventually, this will be a moot point when cable card DVRs go public, and DVRs will be as easy to buy as cable modems are now.

[Doug]

I'm interested to read the comments about the Motorola HD box. We tried the HD service for about two months and I was always confused about the settings/instructions/non-intuitive menu for resolution settings. But that's not the reason we decided to return the box and switch back to OTA for our local digital channels. I strongly disliked the channel guide. You can only display 4 or 5 channels at at time, as the bottom quarter of the screen is wasted by advertising. Also, you cannot block out the channels you do not subscribe to. Navigating just took too much time. I was content to go back to analog cable and a personal DVR.