Distorted Video

[mike300]

I transferred an episode of Lost to my PC using TiVo Desktop 2.3 from my dual-tuner with 7.3. Everything went fine, but when I play it back using Windows Media Player there is a small distorted line at the top of the video across the whole screen. Does anyone know what could be wrong?

[l2bengtrek]

If it's like a line of white dots/dashes (lack of a better description!) I've seen what you're talking about. I see it too. It's probably that way on all transferred files.....bottom line is that you don't see it if you play it back on regular TV's so I don't know if it's something that can be remedied.

[greg_burns]

http://www.tivocommunity.com/tivo-vb/showthread.php?t=291814

[gconnery]

You're talking about the so-called "line 21" or VBI (vertical blanking interval) which isn't seen on the TV due to overscan (the particle beam is returning to the top for the next scan I think). Anyway there's a variety of stuff that can be encoded there--closed captions, V-Chip program ratings, the free TV Guide stuff on PBS channels, channel name, I think there's even some auto-time setting stuff. Anyway, its all a normal part of the TV signal. You'd kindof expect the player to suppress the display of this stuff, since its not part of the normally seen image, but the CODECs need to pass it along so the player can display closed captions and such. You might try another player--Zoom Player or Media Player Classic perhaps. I'm not sure if they solve this better than WMP.

[jmemmott]

You're talking about the so-called "line 21" or VBI (vertical blanking interval) which isn't seen on the TV due to overscan (the particle beam is returning to the top for the next scan I think). Anyway there's a variety of stuff that can be encoded there--closed captions, V-Chip program ratings, the free TV Guide stuff on PBS channels, channel name, I think there's even some auto-time setting stuff. Anyway, its all a normal part of the TV signal. You'd kindof expect the player to suppress the display of this stuff, since its not part of the normally seen image, but the CODECs need to pass it along so the player can display closed captions and such. You might try another player--Zoom Player or Media Player Classic perhaps. I'm not sure if they solve this better than WMP.

For some reason, this issue seems to generate many half truths that forever muddy everything. The information you are seeing is the line 21 VBI data but the "problem" is specific to only some Tivo models. Tivo needs to preserve this information for every show because as you point out it can contain a lot of useful stuff : Closed Captioning, ratings, Tivo popup flags, etc. Although there are no standards, there are several different schemes for saving this information within an mpeg program stream. Which one is used depends on which mpeg -> analog converter chip is being used (Tivo needs the help of this chip to get the line 21 data back into the right place in the VBI part of the analog signal before it sends it to the TV). The older Tivos strip out the line 21 data and store it outside the video in user data elements in the PES. Newer Tivos with the newer integrated BroadCom chips store it as luminescence data in the first row of mpeg macroblocks within the video. When the broadcom chip converts this back to analog, it strips this row out, reinserts in into the right place in the VBI and sends it on. A non-broadcom mpeg decoder doesn't know it is suppose to do this and treats it as real video information. Since it contains only luminance and no chroma data, it is a line of black and white noise. Short of being able to clip the first row of macroblocks, I don't see any way to get rid of it.

PS - it is not overscan. Your TV may have overscan but mpeg files don't...