Fast forward artifacts

Discussion in 'TiVo Series3 HDTV DVRs' started by Ivomir, Jan 24, 2007.

  1. Ivomir

    Ivomir New Member

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    Apr 5, 2006

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    Hi

    I got an HDTV few days ago and started seeing some artifacts when I do 2xFF or 3xFF.

    They appear when there is a big change in brightness somewhere on screen. Visually they are areas of the picture where every other line is very bright (or very dark).

    This happens on every SD channel I tried, as well as recorded shows. It doesn't happen on HD channels, or when I do 1xFF.

    My explanation is that Tivo can't keep up decoding the video and starts dropping frames. Since most frames are deltas, dropping a frame can desync the decompression and corrupt the next few frames. Since in SD the video is interlaced this only shows in every other line.

    I don't have a problem with this if it is a normal behavior. My concern is that it may be a hardware problem.

    Have you guys seen this?

    Thanks
    Ivo
     
  2. cbono

    cbono New Member

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    Nov 18, 2004
    Hmm.

    I've noticed that when I FF through a sequence that has a sudden burst of bright light (explosion, night-->day, scene change, etc.) I get an "interference" pattern that looks like a bunch of diagonal lines ... kind of like some signal dropout blip. Hard to explain. Maybe I should film it?

    Anyway, I never noticed it before the S3. Then again, I didn't watch HD before my S3, so it could be something to do with my TV.

    Interesting someone else is describing what sounds like a similar phenomenon.
     
  3. TAsunder

    TAsunder Debates Ghee vs Gi

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    If it's the same magenta and neon green lines I'm seeing, then it's more than an artifact, it's a major FF problem (similar to the one I have on fox HD, but that one just has time jumping) where several seconds (up to one minute) of video is skipped in that one brief moment.
     
  4. Ivomir

    Ivomir New Member

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    Apr 5, 2006
    If I pause during a 2xFF most of the time I can get the artifacts to stay on screen. I did a couple of screenshots this morning. Notice the interlaced spots.

    [​IMG]
    [​IMG]

    Please tell me you are getting this too (and it is not a problem with my hardware).

    Ivo
     
  5. TexasAg

    TexasAg New Member

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    Apr 2, 2006

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    No offense, but those pictures make it look like the image is completely watchable while you are fast forwarding. You can easily tell where you are in a program when it is fast forwarding, right? Does it really make a difference that there are some artifacts when you are watching a program at 4 or 8 times normal speed?

    Also, just curious - are you on Fios? If so, there are some known FF problems with the Fios signal. I use the 30-sec skip anyway, so I never really notice it.
     
  6. Ivomir

    Ivomir New Member

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    Apr 5, 2006
    None taken :) :
    So if you are seeing the same thing when you FF, I'm happy.

    No, I'm on Time Warner Cable.

    I'm guessing what's happening is the Tivo skips 10 frames, decodes one even frame, skips 10 frames, decodes one odd frame. The even and the odd frames are 10 frames apart, and you can clearly see the difference. It would look better if it skips 20 frames, then decodes one even and one odd frame - then the two will be contiguous and will compose one clear image.

    The S2 doesn't have that problem, and I didn't see it on the S3 with a 27" CRT. So I wonder why is there a difference. Maybe it is a composite vs HDMI thing.
     
  7. pmrowley

    pmrowley Member

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    Apr 4, 2002
    Irvine, CA
    I just started seeing this effect too, after having a major scare with losing all of my Now Playing data a few days ago. After rebooting, I noticed these artifacts appearing, and was worried that there were encoding issues. Fortunately, it looks like the issue is with the FF function, and not the encoding functions. I'm on Cox Cable, with 2 cards, and I can say with 100% certainty that this effect is something new.

    Did a software update get pushed in the last few days? My current image is 8.0.1c

    -P
     
  8. Ivomir

    Ivomir New Member

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    Apr 5, 2006
    I have 8.0.1c as well, and I've had it since the day I got the S3 and it did the service connection (more than 2 weeks ago).

    I started noticing the problem after replacing the CRT TV with an HDTV few days ago. The change involved some rearranging of cables and a couple of reboots. After one reboot I got a green error screen saying the Tivo will try to repair itself. It did complete in a few minutes, and aside from the problem mentioned here, I don't see anything wrong.

    So it may be:
    - visible on the CRT but I haven't noticed it before
    - visible only on the HDTV
    - related to the green reboot screen
    - related to a software update

    Ivo
     
  9. Ivomir

    Ivomir New Member

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    Apr 5, 2006
    P.S.

    I did some more testing, and it turns out the problem doesn't show if the Tivo is running in 480p (and of course Hybrid). But OTOH the picture quality is much worse, because the TV's upscaler is not as good as Tivo's.

    I can see the problem in 720p and 1080i, and it looks the same.

    I tried messing with the video smoothing option, and tried a reboot, but they had no effect.

    Again, I don't mind the artifacts if it is a normal behavior, I'm only concerned that my Tivo may be defective. I've had it for 3 weeks, and now's the time to exchange it if I have to.

    Please respond if you can reproduce this (or you can't) on your Tivo - play an SD recording on HDTV in 720p or 1080i, and fast-forward on speed 2 or 3.

    Ivo
     
  10. Ivomir

    Ivomir New Member

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    Apr 5, 2006
    I am happy to report that the 8.1 software fixed the problem. It also fixed another problem I was having on some channels (USA, Sci Fi): When fast forwarding between the show and a commercial, or between different commercials, there was a single frame showing thick horizontal stripes from both programs. It seemed to be caused by different resolutions or bit-rate of the two programs. After getting 8.1 this doesn't happen any more.

    Thanks, TiVo!
    Ivo
     

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