Why are certain Netflix shows jittery on certain devices and not others?
February 28, 2012 11:11 AM   Subscribe

Why are certain Netflix shows jittery on certain devices, while other combinations of devices/shows are not?

I have three devices at home (aside from my laptop) that can stream Netflix. For a long time now, if I stream a Netflix program on my Tivo or Roku, there is a chance that the program will be jittery.

By jittery, I do not mean that frames start getting sporadically dropped here and there like you would see with a bandwidth or CPU load problem, but that from the first second of playback to the last, there is maybe one frame missing every 24 (just to give an estimate). Jittery-ness never starts in the middle of a show or stops before the end.

If I find, on one of these devices, that the program is jittery, then I know it will be jittery on both devices. And, no matter how many times I try to restart playback, or what time of day or what month I try it, it will always be the case. On the other hand, if I play the same program with the Wii or my laptop, it will never be jittery.

One difference between Roku/Tivo and my Wii is that the Wii does not stream HD but the other two do. So, I tried setting my Roku to SD and it still had exactly the same jitters. Aside from that my laptop does HD fine. All three devices are hooked up to the same router via ethernet (and my laptop is wifi), so it is not a wifi issue.

Examples of programs that are always jittery:

- Lilyhammer series
- Downton Abbey series

(It is not exclusively TV shows, but I can't recall any specific movie titles at the moment.)

I have been surprised to see little discussion of people with similar problems, as it seemed to me that it had to be a video-encoding issue. But if it were then lots of people should have been complaining about Downton Abbey and Lilyhammer. So I am stumped.

My hardware:

- Tivo HD (not premiere)
- Roku 2 XS
- Wii from 2008
posted by kosmonaut to Computers & Internet (7 answers total) 2 users marked this as a favorite
How are the three devices hooked up to the TV? Have you tried different input methods (component vs. HDMI vs. DVI)? Also, both Downton Abbey and Lilyhammer are shot in 1080i, so it might be a de-interlacing issue.
posted by clorox at 11:27 AM on February 28, 2012

Best answer: This is usually known as "judder", and is caused by frame rate mismatch between the rate of the source material and the rate your player is playing back at. I've noticed judder on a lot of material on my Roku, generally stuff shot on film or shot to look like film (24fps). People are indeed talking about it on the net, such as here and here. The general consensus is that the Roku isn't capable of 24fps playback, and instead tries to shoehorn it into 60fps, which is obviously not evenly divisible, so it has to either drop or duplicate frames. The Wii is probably doing pulldown on the 24fps material, so you don't see the judder.
posted by zsazsa at 11:30 AM on February 28, 2012 [2 favorites]

Best answer: Is that a PAL vs NTSC issue? Maybe some devices handle the conversion better than others? Both of those shows would have been filmed in PAL (I believe, based on their countries of origin)
posted by JJtheJetPlane at 11:38 AM on February 28, 2012

Yeah, that is "judder." The shitty Roku we have in the bedroom does this all the time. Everything else we have is smart enough to not have it happen.
posted by Threeway Handshake at 12:12 PM on February 28, 2012

Response by poster: Okay, using the links provided by zsazsa, I found the various test videos available on Netflix (search "Example" and you'll find videos like "Example Short 23.976", Example short 24" and so on). They are encoded at different framerates so you can identify judder (and thanks for telling me the correct name as well!).

The results:

- Example Short 23.976: no judder
- Example Short 24: no judder
- Example short 25: judder!

So, it would seem the judder occurs with programs that are encoded at 25 fps. As I understand, 25 fps is the PAL standard, and so JJtheJetPlane appears to have guessed correctly! As far as I can see from these Netflix tests, the 24fps/60fps thing is apparently not an issue anymore.

Now, I don't see a way to find out the framerate of any Netflix program, but... Downton Abbey is certainly from a PAL country, and Lilyhammer is shot in Norway so it could easily be PAL.

I may be falsely remembering theatrical movies having judder — perhaps it has only been certain TV shows, specials, and originally made-for-TV movies that have had this issue.

(Incidentally, I tried randomly selecting about five random British TV shows and none of them had judder.)
posted by kosmonaut at 1:43 PM on February 28, 2012 [1 favorite]

Just as an extra data point, I've watched S1 and S2 of Downton Abbey on a Roku with no judder at all.
posted by yoink at 2:01 PM on February 28, 2012

Response by poster: yoink
See, now that's baffling! What version of Roku, and how is it connected? Are you able to watch Netflix's Example Short 25 without judder?
posted by kosmonaut at 2:49 PM on February 28, 2012

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