Judder/studder in blu ray rips

[Vilago]

I am using the WDtv live to play my blu ray rips. Some files, after ripping, play fine in VLC but on the live motion does not seem "smooth" and there is a fair bit of judder which unfortunately is distracting to the point of annoyance.
It appears like a frame rate issue, possibly dropped frames.
It seemed isolated to the harry potter movies at first so i let it go. Now it's back for a different movie which has me worried that the issue may be more widespread.
I have tried reseting, rolling back the firmware, using a different hard drive (i'm playing the files locally over USB) and nothing helps. The same file plays fine on my computer through the same hard drive in VLC so that eliminates a hard drive defect issue or ripping issue. It looks like the live is struggling with these specific files for some reason.
Since I have a hard time describing the issue, I'm posting a youtube video of the problem (see below)

Look at the motion in the scenes and how it isn't smooth. There is some very noticeable judder.
The judder isn't random, it appears in these same spots in the movie when I play them over and over again. If no one has seen this before, I'll try posting in the WD forums but I hope someone else has this same problem.
for the video, watch the pumpkins as the lighting flashes, and then when nevil moves around. it's like the flashing is somehow making the framerate hiccup....
keep in mind this issue is much more pronounced in real life. (this isn't the only time it does it, but is the most visible example i could find)

http://www.youtube.com/watch?v=1f2Ogy5a ... e=youtu.be

I have tried posting in the WD forums and avsforums. They claim it is a problem with the file itself since converting to m2ts fixes the problem, but when converted back to mkv still exhibits the issue.

and if all that wasn't enough, here's a link to a clip of an exact file that exhibits this issue. i tested it on my live to verifiy that clipping it didn't change anything.

http://dl.dropbox.com/u/56152042/Potter.mkv

sorry about the large file size, i don't compress my blu ray rips.

Also, one final thing, i noticed that after updating to the newest version, the studder is JUST...ever...so...much better than it was before which is leading me to suspect there might be some weird error in the ripping routine. hopefully this will get figured out. i know makemkv has a better track record than WD for fixing problems at least. lol

[DaveQ]

It seems likely that the stuttering is due to the bit rate exceeding that which your WDtv live can handle. The bit rate varies from scene to scene depending on how difficult the scene is to encode/decode efficiently. One clue is the lightning flashing, which will cause the bit rate to spike briefly as the entire frame changes from one moment to the next.

You can test to see if this is the case by encoding the problematic scene (or chapter) with Handbrake, using a constant quality setting of around 21. This should bring the bit rate down quite a bit compared to the uncompressed blu-ray rip, and if the resulting chapter(s) or scene(s) play smoothly, you have your answer.

Dave

[DaveQ]

Okay, so I downloaded your Potter.mkv clip. For what it's worth, it plays smoothly on my Mac using Plex, no stuttering. Bit rates vary from moment to moment between around 14 Mb/sec up to the mid 20s Mb/sec.

I used HandBrake to encode your clip with my fast conversion settings and CQ factor 21. The new clip varies in bit rate from around 3 Mb/sec to around 12 or 13 Mb/sec, and also plays smoothly. If you want to download it and see how it does on your WDtv, you can find it here:

http://www.filedropper.com/potterencoded

Dave

[Chetwood]

An easier way would be to test this by remuxing to m2ts. Also, I've read somewhere that 50 Mbit/s is fine for the LIVE so I doubt it's due to peaks.

[DaveQ]

An easier way would be to test this by remuxing to m2ts.

He said in his original post that converting to m2ts fixes the problem, and that converting back to mkv causes the problem to recur.

Also, I've read somewhere that 50 Mbit/s is fine for the LIVE so I doubt it's due to peaks.

I'm thinking (based on what he's tried already) that it might have trouble with the uncompressed bit rate when the video is in an MKV container. If he wants MKV, then perhaps reducing the bit rate by re-encoding will eliminate the problem. He can test it by downloading the clip I re-encoded and trying it on his WDtv live.

NOTE: Don't judge the video quality of any clip in VLC. As cool and flexible as that software is, it sometimes produces video artifacts on clips that other playback software plays fine. For an example, see:

http://forum.videolan.org/viewtopic.php?f=12&t=108422

Dave

[Vilago]

Yes, I think that's the case too. Most of my movies play fine from what I can tell, including movies that are much larger in size. I had someone remux to m2ts and it fixed it, but when remuxing back to mkv the problem was still there.

[DaveQ]

Vilago, I made a reply to Chetwood's post but it hasn't shown up yet. (It's waiting for a moderator to approve it because it included a link.) Basically I'm guessing that the WDtv live may have problems with the bit rate when it's pulling a video stream out of an MKV container. (I had noticed your comment in your first post about everything working fine when it was m2ts.)

I'll go further here and say it's nearly impossible for MakeMKV to be doing anything to cause this problem. MakeMKV doesn't actually change the video stream; it simply extracts it and leaves it, unencrypted, in an MKV container. The video stream you get out of the MKV container is the same video stream you get out of the m2ts, assuming you aren't re-encoding.

The test I proposed is pretty simple. Download the re-encoded version I made and try it on your WDtv. That file HAS been re-encoded to a smaller average and peak bit rate.

Dave

[Vilago]

yeah i will try that when i get a free minute soon. i never really thought it was makemkv's "fault" but had to at least consider that option to cover all bases.

thinking about your theory, it actually makes a lot more sense to me and seems like it could actually be the right one. let me try your file and i'll also tell WD about it too.

[Chetwood]

The test I proposed is pretty simple. Download the re-encoded version I made and try it on your WDtv. That file HAS been re-encoded to a smaller average and peak bit rate.

Which still doesn't rule out possible positive side-effects of the remuxing process.

[DaveQ]

The test I proposed is pretty simple. Download the re-encoded version I made and try it on your WDtv. That file HAS been re-encoded to a smaller average and peak bit rate.

Which still doesn't rule out possible positive side-effects of the remuxing process.

In his first post on this thread, Vilago said:

[...]converting to m2ts fixes the problem, but when converted back to mkv still exhibits the issue.

This would seem to rule out positive side effects of remuxing as the determining factor, though it doesn't mean there isn't some difference in the containers that the WDtv is sensitive to.

It's somewhat difficult to troubleshoot anyway, given that his original problematic clip plays smoothly for me. That said, if the re-encoded clip I provided plays smoothly for him, it at least points him toward a possible workaround.

Dave

[Vilago]

Okay, so I downloaded your Potter.mkv clip. For what it's worth, it plays smoothly on my Mac using Plex, no stuttering. Bit rates vary from moment to moment between around 14 Mb/sec up to the mid 20s Mb/sec.

I used HandBrake to encode your clip with my fast conversion settings and CQ factor 21. The new clip varies in bit rate from around 3 Mb/sec to around 12 or 13 Mb/sec, and also plays smoothly. If you want to download it and see how it does on your WDtv, you can find it here:

http://www.filedropper.com/potterencoded

Dave

Hey dave can you reupload? the link doesn't work and i tried typing it in manually.

[DaveQ]

Vilago, I PM'd you with a new link. Didn't post it here because forum posts with links in them are delayed until a moderator can approve them.

Dave

[Vilago]

Sorry for the long delay, i've been pretty busy.

Dave, I had a chance to test your file...it works!!

it isn't makemkv's fault after all.

maybe it's very possible we have isolated the issue to very very transient peak bit rate spikes that somehow don't appear when you do a bit rate analysis.
...or something changed during the re-encode.

In any event, i'll tell WD about our findings and post the compressed file. hopefully (but not likely) WD will fix this.

meh this is annoying!