Motion judder

I highly, highly doubt it has anything to do with the atv. Mine is as silky smooth as a baby behind. The problem may be LCD. I hate lcd tvs.. they suffer from what some people refer to as "screen door effect". I stuck with plasma.. for that natural motion and colors. Try it on a different TV and see if you can. But again, doubt its the ATV.

Have you seen the same movie on DVD to say it's definitely related to AppleTV playback?

Juddery motion can be due to a number of things:

- usually happens with fast pans when you become aware of unnatural motion effects
- older movies/shows tended to have far slower pans than newer ones
- poor encoding of the source video for AppleTv could be responsible
- too complex encoding of source material for AppleTv could be responsible (it struggles to keep up with frame creation), but seems unlikely
- network not keeping up for streaming leads to juddery motion (not here)
- TV processing/display not capable of reproducing smooth motion

If you're happy with playback from DVD and haven't noticed big issues then I suspect it's AppleTv and the file encoding. Out of interest, how are you connecting your DVD player and is it an upscaler or not?

I watched Disney's Enchanted in HD last night on the 1080p setting and there's quite a lot of fast movement/action in that in places and I didn't really notice many motion artefacts, and my Panasonic plasma is not the best when it comes to motion judder in panning shots.

I don't know either what refresh rate the 1080p is, but given that AppleTV cannot officially decode any higher than 720p at 24fps (which is then upscaled to 1080p rather than being 1080p source resolution), it could be a case of a movie being 24fps causing issues played back at 50Hz or 60Hz via your Tv, whereas your PAL DVDs are usually encoded at 25fps.

AC

I've seen a quite impressive demonstration of such judder in my local TV shop. He had a few regular LED displays (all current models) and some higher priced ones next to each other. It was the same picture being fed to the different displays simultaniously ...and many of the regular ones did exhibit what you discribe as judder.

I guess the cheaper ones must save their money somewhere ...

I think a heck of a lot of it depends on the encoding of the file, and just because we may be buying/renting shows from Apple does not necessarily mean that they are encoded with the best possible parameters even though it would be logical to think the movie companies would want to maximise quality for their wares. In fact I suspect they delibereately do not encode them as well as they might as they are so paranoid in case copy protection is circumvented in some way.

I can remember my first TV Show purchase from Apple was an episode of Lost - there was a lot of judder in panning shots, so I went to Blockbuster and rented the DVD which looked at a lot better.

Despite all the hype about h264 compression being equivalent to MPEG2 encoding at lower bitrates, network capacity and server capacity probably dictate that we get poorer quality encodes than are actually possible as they try to keep file sizes for download to a reasonable size. Add to the equation that they probably think lots of stuff will be watched on an iPod/iPhone and quality vs size becomes part of the marketing dichotomy.

I've often felt it would be nice to have a couple of versions for download for your fee - low res/low bitrate for iPod and higher res/bitrate for AppleTV or computer.

AC

tokyobeing wrote:
I've seen a quite impressive demonstration of such judder in my local TV shop. He had a few regular LED displays (all current models) and some higher priced ones next to each other. It was the same picture being fed to the different displays simultaniously ...and many of the regular ones did exhibit what you discribe as judder.

I guess the cheaper ones must save their money somewhere ...

Absolutely, and consumer electronics is a cut throat market - a few years ago a plasma would have cost several thousand pounds, but they can now be had from about £500 for a 37" model upwards. I bought a 42" Panasonic last year which is great, but not perfect - excellent value for money but the replacement improved model is only about 60% of the cost a year or so later. Build quality and quality assurance must suffer.

I've been eyeing up a Pioneer LX5090 which is still very expensive in comparison to the Panasonics, but the extra costs relate to far higher quality video processing circuitry, and also a smaller market share.

AC

What do you mean by judder, are you referring to longish pauses with a stop start type of effect or something altogether more minor but nonetheless irritating.

I wouldn't be concerned about the refresh rate (MHz), if the tv has only given you one option then it has already eliminated the refresh rate that doesn't match your tv.

Winston Churchill wrote:
I wouldn't be concerned about the refresh rate (MHz), if the tv has only given you one option then it has already eliminated the refresh rate that doesn't match your tv.

Yes, there may not be much to do in that respect, but if the video is say 24fps with a 50Hz Tv display, I don't think we really know what AppleTV does in terms of frame rate conversion, and it may not be pretty. Different TVs have widely differing processing and what might look good on one set could look jerky on another.

AC

Message was edited by: Alley_Cat

Agreed, I also have no idea how the tv deals with varying frame rates, although my guess would be that it doesn't and there is no conversion. After all the tv has to cope with frame rates other than 30/25/24 and would need to work to a whole bunch of conversion algorithms covering the eventuality of not only many possible frame rates but also two different refresh rates.

One way of coping with various frame rates would be to play them frame for frame in the same way that 24 fps video is played on a PAL system, resulting in the media being speeded up or slowed down. Whilst this is essentially unnoticeable for 24 fps playback on PAL, it would certainly be noticeable for video encoded at 12 fps for example, since 12 fps video suffers no such speeding up on the tv, it's likely safe to assume the tv does not employ this technique.

Simply playing (for example) 24 fps content at 25 fps will result in tearing as the image changes in the middle of a single scan, again I don't particularly see any evidence of this on my tv's but it may be slight and unnoticeable and indeed may depend on the tv itself.

Even if we could see the motion judder, it would be quite difficult to determine why it occurs, indeed as you point out it may well be an issue introduced in encoding or even one of peak data rates, not being able to see the OP's problem makes it even more difficult, but a restart of the tv may help in some cases.

Yes, I have the same issue. I have 2 ATV's and everything I have watched in HD so far has been almost unwatchable because of the judder. The files play ok(ish) on my iMac, but there is still some noticable judder in fast motion.