Consistent image shudder during payback of mkv files

[cinesimon]

Hello there!
I've asked this at other sites, and have had no luck - so thought I'd try here. I can't see any hint of this being discussed here but if it has, my apologies - and please point the thread out to me...
During playback of an mkv file - regardless of size or resolution(720p-1080p, 4gig-10gig), and whether I play it using my computer, my Western Digital WD TV media player, even on DVD after converting with convertxtodvd, there is a consistent shudder in the image. There is no other way to describe it - you'll know what I mean if you've seen it.
The frequency is about every second, and it's throughout the entire film. It is always there, but I've noticed it can sometimes be not so noticeable, sometimes very annoying - of course it's extremely noticeable during long pans and zooms, but I'm sure there is a variation in intensity also: that is, on some rips it's not so intense, sometimes the film is unwatchable the shudder is so intense. The intensity of the shudder is consistent throughout the film.

So does anyone know what I'm on about, recognizes it and knows a solution?

Though I consider myself technically proficient in general sense, in this field I'm not so knowledgeable so please excuse my lack of terminology and knowledge - especially if you need to ask further questions to help me figure this out - if you choose to!

Thanks in advance,
Simon in New Zealand

[poisondeathray]

What software for playback, and what computer specs?

Maybe you have a bad video? or whoever made it didn't process/rip it correctly? It seems unlikely that both your computer and WDTV would exhibit the same behaviour, unless your video is like that to begin with

What is the source? 23.976 fps "film rate" is often "juddery"

What about other video files?

What about other containers? e.g. remux into .mp4

[Baldrick]

Play using MPCHC (maybe with reclock also) and adjust your monitor/TV to match the framerate of your source(24fps=24hz/48hz/72hz).

[Squash]

As poisondeathray pointed out above about "film rate" being juddery, it sounds like you might be particularly sensitive to "temporal sampling judder": the 24 frames per second rate of film is not sufficiently rapid to convince you of smooth motion, particularly in pans and zooms. It drives some people nuts (I'm one of them). If that's what it is, then it's nothing to do with the MKV container; that just happens to be what your "rips" are packaged in.

It only started bugging me when I got a large-ish TV; I passed some sort of scaling threshold where the movement steps were no longer fluid. The solution for me was to get a TV with frame interpolation. Many people condemn this approach, but it works quite well for me and others. You can also do the interpolation yourself on your computer using avisynth scripts if you're so inclined.

There've been a few threads on the subject here; this one got pretty nasty before it was over:
https://forum.videohelp.com/threads/305001-Current-HD-standard-is-a-FAIL
It starts slow, but stick with it for a while.
The original poster felt insulted here at Videohelp; after he left the conversation continued over at doom9:
http://forum.doom9.org/showthread.php?t=146795

If that's not it, then never mind.

[cinesimon]

Squash that's really interesting.
I did begin to notice this on my projector, and then on my computer monitor when I paid more attention.
Big BUT though: it's only with HD - is the theory still valid when I don't have this problem with DVDs whatsoever?
I only see this with HD rips - never ever on DVD.

[creamyhorror]

Are your HD rips encoded by yourself or by someone else? If you're making them, you could be introducing a problem during the encode. Do you watch any Blu-rays?

[cinesimon]

They're scene torrents. All of them.
I have thousands of legit DVDs, and don't want to replicate them by getting the bluray as well - still dodgy I know, but hey I own the films!
That's my justification, anyway!
I've asked at the private torrent site I belong to, and they apparently don't see an issue - so it may well be that it's me, as Squash says above. Never knew it could be an issue! I thought the only issue like that was some people being susceptible to 'the rainbow effect' on DLP projectors. Though I still haven't figured out if that is the actual issue here - the fact that I don't see the problem on DVDs(or any other file format) is of concern: I'm trying to figure out if the 'physiological' issue Squash describes is particular to HD.

[cinesimon]

By the way - it's certainly not a 'juddery' issue: I recognize that issue, especially with lower kbps rips.
It's a 'shudder' - or even a 'pulse' - with a frequency of roughly every second, consistent throughout the film regardless of camera movement. But it's much more noticeable during smooth camera actions like pans and zooms.

As for the initialll queries: my system is XP, dual core 2.8 about 5 years old. It plays HD xvids absolutely fine with either vlc or mpc. The video card was the best Dell could offer during the time - apparently it;'s styill pretty damn good.
Still: given that my WD TV is exactly the same, it's obviously not my computer or any software - unless it's possibly Vuze? But I doubt that.

I'm checking to see whether I can match my projector, the WD TV and the file's framerate - that would be amazing if that's all it was: mismatched frame rates!
Will check same with my computer & screen.

Hey thanks everyone for your input so far - plenty of things to explore.
Really appreciated.

I hope it's not my brain!!!

[poisondeathray]

no, 23.976 judder is well established. Just google it and look in the avs forum, you'll see 100's of posts on it

as squash said, "purists" won't touch anything that frame interpolates. They would argue that original cadence is how the director meant the artistic piece was meant to be viewed

the fact that I don't see the problem on DVDs

you should technically see a slightly different judder with DVD. It's actually more pronounced, because of the way the 24fps is stored with 3:2 pulldown. On blu-ray you can get native 24p (or 23.976p)

[poisondeathray]

By the way - it's certainly not a 'juddery' issue: I recognize that issue, especially with lower kbps rips.
It's a 'shudder' - or even a 'pulse' - with a frequency of roughly every second, consistent throughout the film regardless of camera movement. But it's much more noticeable during smooth camera actions like pans and zooms.

This is an entirely different issue. It's from long GOP and low bitrate. Keyframe pulsing. It's because the bitrate is too low for that particular content complexity. Because the P,B frames are significantly lower in coded size, and they code the differences between frames, the quality drops significantly until the next higher quality I-Frame, which suddenly "pops" as the quality improves. It's worse with movement, because there are larger differences between frames (i.e. higher content complexity)

[cinesimon]

Wow - that's beginning to sound right poisondeathray! The 'pop' certainly makes sense to me in an abstract way.
But would EVERY release from 'scene' groups have that issue? Very common releases: 720p, about 4.4 gig, 4-5000 kbps?

And yes I do see the judder on DVDs, but I have a very very high end DVD player, which likely reduces that a lot.

So it sounds to me like I need to either get a bluray and start buying legit bluray releases, and/or only download high(well above 5000kbps) kbps torrents. T hat sound about right, and I'm likely on the right track?

Again, thanks so much. Disappointing to learn I'll have to be more patient(d'oh!), but hey - I always had a feeling that many available torrents were too good to be true.

[poisondeathray]

Without examining a sample, I cannot say for certain. I don't know much about "scene" group releases, or how well they do their encodes. But from your last description, this suggests what is going on.

Remember , this all depends on the content complexity. So for action movies (with explosions and lots of movement), they would typically require a much higher bitrate for a certain level of "quality" than a slow moving drama, for example. The scene release, by artificially enforcing a size limit (I know there are "rules") , they don't do optimal encodes

[cinesimon]

Yep: likely I'll have to be more selective. And start looking at upgrading my collection earlier than I was wanting to.
If I want to watch films without cursing, that is!

Re content complexity: would that not also apply, though, for a simple image that is very 'dense'? Or is that just my ignorance shining through?

[poisondeathray]

Re content complexity: would that not also apply, though, for a simple image that is very 'dense'? Or is that just my ignorance shining through?

This is all relative; that is relative for a certain level of "quality" and bitrate.

By "dense", if you mean more noise, or more detail, yes. e.g. A scene with a blank wall will take less bitrate than one of a forest.

If you're talking about single images, there is no temporal component. i.e it's all intra frame, so there are no long GOP, or P, B frames. There is no motion. But the relationship with content complexity still applies with intraframe compression. You can even see relationship this with still photo cameras and jpeg compression (i.e. a "complex" picture will not compress as well as a "less complex" picture, and the former will require a higher bitrate)

So it sounds to me like I need to either get a bluray and start buying legit bluray releases, and/or only download high(well above 5000kbps) kbps torrents. T hat sound about right, and I'm likely on the right track?

You can't answer that without knowing the content complexity, at least in general terms. e.g. a cartoon release will compress much better than an action movie. You also have to factor in many other things like encoder settings (were they good), preprocessing (did the guy know what he was doing), frame size (5Mb/s for 1080p is quite low). In fact, most retail blu-ray barely have 720p lines of actual resolution (the frame size might be 1080, but the actual resolved detail is much less). Encoding at 1080p is usually a waste for most Hollywood releases (some exceptions with CGI)