Sub channel in 480i and 16x9?

[Dah-Henny]

This one's got me scratching my head. I scanned in a channel last night, WGHP channel 8 from the triad area of NC. 8.1 is HD, and 8.2 (Antenna TV) is in SD. I was checking the info from the station, and I noticed that 8.2 was broadcast in 480i, 16x9. All of the sub channels on other locals are 480i 4x3. I have all SD channels on my 722 set at full zoom, but 8.2 doesn't full zoom without also changing ALL HD channels to full zoom. The problem with the 16x9 on 8.2 is, all of the programming is 4x3, on a 16x9 format.

The pic shows 4x3, in a 16x9 format, if that makes sense. Any of yall have channels like that?

 

[Tower Guy]

I noticed that 8.2 was broadcast in 480i, 16x9. All of the sub channels on other locals are 480i 4x3.

The pic shows 4x3, in a 16x9 format, if that makes sense. Any of yall have channels like that?

None here.

By transmitting a 4X3 picture with sidepanels the effective resolution is decreased because fewer pixels are filled with picture elements. The MPEG2 coefficients for the sidepanels are all zeros. That makes the picture quality of the subchannel lower, but allows more bits to be allocated to the main channel, causing it's picture quality to increase. CATV systems can use 544 horizontal pixels with 4X3 video to achieve the same goal, but 544 is not an over the air standard. Yet a few stations have used 544 and it seems to work.

 

[foxeng]

I can answer this since I work there.

Yes, it is 720x480i but anamorphic with the 16:9 bit set to be sure the the display formats the picture correctly. The network programming is 4:3 with anamorphic format added locally, but when we start to add local commercials, they will be in 16:9. The signal path we are using is an all digital anamorphic path so it does not have the analog artifacts of PQ degradation that you see when this is done with an analog signal. Any analog in the path would show PQ degradation but not with SDI.. FOX network also used 4:3 anamorphic in network distribution in their pre HD days of "FOX Digital Widescreen" from 2001 to 2004 as well with an all digital path. We used this same set up for over a year on our main channel with no viewer complaints while we converted our master control to HD. We have had no viewer complaints on 8.2 either.

 

[Mr Tony]

The pic shows 4x3, in a 16x9 format, if that makes sense. Any of yall have channels like that?

yes...partially
A station I can pick up (KEYC) has CBS on main and Fox on subchannel (its the only channel in the market). During Primetime (and during sports) KEYC-DT2 is 16:9 otherwise its black bar hell. Station is in 480i

My thread on it from this past summer
http://www.satelliteguys.us/digital-over-air-ota/213368-station-480i-hd.html

 

[Dah-Henny]

Thanks for the reply Ice, and thanks foxeng and Tower Guy for explaining the tech of it.