Impossible Interlacing Problem

I’ve been observing this and I think it dawned on me what is going on… I’ve been seeing some terrible interlacing (combing) on my 720p stations. These stations broadcast at 720p… so what is going on? Specifically:

  • Morning news programming looks fine at 720p
  • Commercials often have terrible interlacing characteristics (combing, window blinds, etc.)
  • Tablo is set to 720p encoding
If I understand this stuff correctly, Tablo’s 1080 setting will deinterlace 1080i sources. The 720p setting, however, would see no reason to deinterlace a source that is already progressive. BUT, I think 720p stations broadcast some content (in my case, commercials) at 720i.

Can anyone confirm that?

Going further, I think I never noticed this with my TiVo because it was saving the transport stream RAW… and that 720i content was actually 720i @60Hz. Perhaps I had a hard time noticing the interlaced content when it was flipping by at 60fps.

Tablo, however, is encoding everything at 30fps. And, if it is not deinterlacing before capturing those frames… I suppose that could exaggerate the interlacing effect.

We definitely haven't seen interlaced material on a progressive broadcast - this is the first we've heard of it. But, anything's possible. 

The best thing to do (in order to be thorough) would be to grab a sample from your Tablo and take a look at what you're seeing. Can you send me a note here with all the details? We'll set up a remote session.

Text moving sideways example:

Text moving vertically example:

This was a political commercial during the commercial break for the KCRG-TV9 news. (

My Tablo is set to 720p recordings.

Playback device: Roku 3 (gigabit wired) via HDMI to a 720p display

I do not see any interlacing artifacts during the news broadcast. However, very often I can see them plainly during commercials. The examples provided above were seen during playback and captured with the playback paused.


If you need access to my recordings just let me know when to put the TabloTV into the right mode.

@cedarrapidsboy Let’s do that. Easier for us to extract the video that way - can you send me a note?

Noticed something the other morning related to this interlacing problem. I can confirm the station isn’t changing their video format, or something weirdly impossible like that.

Due to several school closings, the local station had a scrolling bar (ticker) at the bottom of the screen.

While there was absolutely no interlacing artifacts in the ticker, a commercial playing above it had very bad interlacing artifacts (like the footage provided above). So, the station seems to be showing interlaced content via the progressive broadcast. When Tablo steps the frames down to 30 (from 60 – as is required for many devices to playback), the interlaced content looks a lot worse (instead of 1/2 image every 33ms you get 1/2 image every 67ms - except for the ticker in this case, that was a full image every 33ms).

I wonder, can you do a decomb filter on progressive stations?