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For awhile now, I've noticed some subchannels showing the 4:3 content with an extra set of pillarboxes. My TV puts light gray bars up when it sees 4:3 content. But on some channels, I see narrower black ones inside the gray ones. I'm pretty sure these extra pillarboxes are being transmitted as part of the 4:3 content (the light gray pillarboxes didn't change in width). Note: I'm watching over the air TV (no cable).

Here's a diagram of what I'm seeing (white center part has TV show):

diagram

At first, I thought maybe the content was actually narrower than 4:3 (old movies), but that's not it because some subchannels are showing 70s TV shows and these are definitely 4:3 content.

Maybe these channels are implementing some sort of newish "anamorphic widescreen" capability so someday they can air 16:9 content on a subchannel meant for 4:3? (I'm guessing. My TV is an older HDTV, so if anything was added in the last 10 years or so, it couldn't automatically handle it).

Anyone know what's going on here? Knowing what it is could help me correct for it.

UPDATE: I found a subchannel that had bars that looked like old fashioned wallpaper (instead of black). Also, I noticed the widths of the bars vary from channel to channel (some are pretty thin, the ones with the "wallpaper" look are pretty wide).

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    This is just a guess but it looks to me like either your tv or the channel itself is incorrectly adjusting the aspect ratio. So there’s a piece of 4:3 content, pillarboxed for 16:9 broadcast, then being squashed back down to 4:3, so you end up with two sets of pillarboxes and an image that’s squished even narrower than 4:3.
    – Jim Murtha
    Commented Dec 18, 2020 at 4:02
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    Tests - depending on you TV's capabilities… 1. force back to 16:9 (my old TV used to misinterpret some channels as 4;3 when they weren't, I had to manually flip back each & every time, it would not disable the auto setting permanently) 2. see if you can find imagery clearly defined as a square or circle & test it for elongation at both 4:3 & 16:9. (Photograph then crop to eliminate distraction)
    – Tetsujin
    Commented Dec 18, 2020 at 12:30
  • I just found a subchannel where the additional bars are made to look like wallpaper. Thus, I don't think this is an accident. My guess is the content providers are expecting you to stretch the picture. It's interesting I couldn't find chatter about it on the internet (hence this posting). So, either most people have setup their TVs to always stretch 4:3 content, or there's a signal embedded so modern TVs automatically stretch it, or no one but me watches these channels :).
    – Adirondack Jim
    Commented Dec 20, 2020 at 14:43
  • Response to Tetsujin: Yes, with some time, I could verify the picture is "squished" and needed to be stretched. But, I really didn't want to digitally record content and look for something that should be round (it would have to be "head on" and not at an angle as well) & then freeze it so I could "analyze it". Too time consuming. So many subchannels in my area are now doing it, I was hoping someone else had seen this phenomenon and knew what was going on. Thanks for the comments though.
    – Adirondack Jim
    Commented Dec 20, 2020 at 16:45
  • If you have Netflix, they have a test program. Or if you can watch youtube on your TV, I'm sure there is a test video there. But your TV might not treat internet content the same as broadcast TV.
    – Acccumulation
    Commented Dec 21, 2020 at 5:22

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OK, no one knows, so I did it the hard way. I watched various channels when my TV was told to show 4:3 content in 4:3 (not stretched in any way) and looked for known round objects (car wheels, clocks, et). I found them to be squeezed. I recorded a channel that had the double pillarboxes on my HTPC and when I played it back, the extra pillarboxes were gone. Somehow my HDTV tuner/player knew the image was being squeezed and automatically stretched it. I did a lot of searching and found there is a bit that tells the TV the image is "squeezed", much like an anamorphic widescreen DVD: link one, link two. The second link is an addendum to the original standard. That probably explains why my TV doesn't auto stretch and no one else sees this--my TV is too old.

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