mkvmerge bug?

[jflatt]

Here's the story, I want to strip the extras from my DVDs and keep them in a friendly, usable format and not lose any quality. I started with Phantom Menace R1 NTSC. As a side note, any chapter and subtitle tools I used bombed out because of the angles at the start. The text scrolling is available in three languages. If anyone wants corrected chapters and subtitles for this disc let me know. Worked fine after ripping to disc and stripping the angles. I have used the mpeg2mkv.exe utility through Wine in the past, and it seemed to create excellent matroska files. I would then merge in my ac3 audio, chapters, subtitles, etc. This was using mkvtoolnix 1.0.1 and libmatroska 0.7.4. Because of some weird gentoo dependencies, I decided to mix things up a little bit so that I can run the latest VLC, which plays these files very well. I then used mkvtoolnix 1.4.2 and libmatroska 0.7.6. mkvmerge will now die with an assertion error when using the mpeg2mkv pre-processed video track. I notice that it can now mux the MPEG-2 m2v file directly now, sweet. But now, during playback, it seems this directly muxed video track has some playback errors I can see in the image. It looks like some strange blockiness in the outer portion of the video, and there seems to be some choppiness in the playback. Happens in mplayer as well. I can get things working by juggling all these different pieces of software, but it would be nice to get this process streamlined. I really like this container format, paired with VLC it really kicks ass. Thanks.

[TonyMo]

I'm not sure if my problem is related to yours, but I too am experiencing blockiness when trying to mux dvd mpeg2 into matroska...

In my case, the problem is 100% reproducable, without using any chapters, subs or even audio.

Here's what I'm doing (please correct me if you spot something I'm doing incorrectly)

I take my DVD, run it through DGIndex and use the m2v file to mux back into matroska, using mkvmergeGUI. I'm using all the latest matroska packs etc, on Windows XP2

Most of the time, it works perfectly, however, when viewing the material, there's an occasional glitch, about 2 minutes out of every hours worth of material so far, which is obviously hard to track down without dedicated viewing habits!

The problem usually occurs at a scene change, and the video will suddenly start exhibiting severe blockiness (see attached screenies). This may either last until the end of the scene, at which point, if you're lucky, the video will revert back to normal at the next major scene change, or will take a couple of minutes until the problem decides to 'reset' itself and video suddenly pops back to normal...

When this happens, it always happens on the same scene, I've remuxed several times with and without the audio tracks etc to try and pin down the problem but no luck so far... A couple of observations which may help are, a) always seems to happen at a major scene change, usually going from bright to dark, or vice versa... also noticed when cutting to an outside scene... b) only noticed this problem on NTSC dvd so far. Not seen on PAL discs at all, but I have a far higher ratio of NTSC discs so that could be a red herring.

Finally, a related problem. As I am usually muxing TV episodes into mkv, I tried with a whole movie. The movie played fine, but I noticed that when searching through the movie, the same blocking problem rears its head EVERY time I do a seek. This time, the blocking stays for a long time, until the current scene fades to black and the next major scene starts (probably coincides with Chapter stops in this case, but again, dont know if related to the problem), minor scene changes do not reset the video as in the TV examples... again, probably unrelated to the problem, but worth pointing out.

Hope someone can help fix this problem, and would be interested to see if anyone else can replicate the anomolies, and to eliminate my particular system from the crime scene....

PS. I've got a (relatively tiny) cut down m2v file if anyone reading this wants to help debug the problem...

Here are the attached examples...

[unplugged]

There may be some bug in MPEG2 muxer part of mkvmerge, I have never had sound sync problems with fourcc based ones (xvid, divx...) but there is one .m2v video that when I mux into .MKV gives out of sync audio after the seek pos. of 22 minutes. (before this position every seek goes perfect)

Even with original audio (not compressed) and even with it played externally with MPC dub mode, after the 22th minute the problem is there.
I can guess that's a video mux problem.

[multicone]

Mkvtoolnix is at 1.5.5 already

[TonyMo]

Problem persists even in 1.5.5....

[unplugged]

Update, oh sorry there is some problem with the .m2v file itself, sorry again mosu.
:( false alarm

[jflatt]

Example 2 looks very much like the same problem

[TonyMo]

@jflatt Interesting to note your problem occured with an NTSC source. I've been through a few more PAL discs since posting my findings and PAL sources all seem to be clear of the problem so far...

[spyder]

@TonyMo

I am interested in this sample m2v file which shows this problem. Please post it here or upload it to Mosu's ftp server. I wrote the mpeg2 parser in mkvtoolnix so if there's a bug I suppose it's my fault. But if you want to you can blame Mosu, it makes me feel better ;)

[TonyMo]

@spyder

Thanks for responding to this, I will try to upload to MOSU's FTP server, as I think the file is a little too large to upload to this board, and no blame attached.... !!! More gratitude than anything. Hope you can find the problem.

I can get some more samples if you need them, just let me know...

Thanks again

TonyMo

PS Ran this through mkvmerge 1.5.6 just to make sure problem still occurs. It does...

PPS. File uploaded to FTP site already. File name: "Tintin Sample"

[j7n]

I just Googled up this old thread. It seems to exactly describe my problem.

I multiplexed the first episode of Lost (PAL 720*576). The blockiness first occured at 0:20, then at 1:23.9 and many more times throughout the video, lasted a few GOPs and then the picture reverted back to normal. Now I remember that I have seen this effect before in PAL DVD of Knight Rider, which I also muxed in Mkvs. Back then I assumed that those DVDs were poorly encoded and forgot about it. However, these VOBs now play back properly without any artifacts!

I used mkvmerge v1.7.0 (What do you take me for) to multiplex M2V + AC-3 + AC-3.
The same artifacts appear if I transmux a MPG made by TMpgEnc.

I like to use Matroska because of precise seeking and less overhead than MPEG-2 PS. Any suggestions?


Decoders:

1) Gabest's Matroska Splitter v1.0.2.9
Elecard MPEG-2 Decoder v2.0.2525

2) VideoLAN 0.8.5


Screenshots, not exactly the same frame.

Original:
http://img112.imageshack.us/img112/9408/bscaporiginalio6.png

Blocky picture of the Mkv:
http://img112.imageshack.us/img112/9522/bscapbadui0.png

I can upload a clip if you feel it is fine concerning Copyright.

[TonyMo]

I think your post is the first report I have seen of this happening on a PAL disc.

I had this problem a long while ago despite sending off files to the relevent guys as requested, it's never been resolved to my knowledge.

I have tried sporadic updates but with no luck... I have since given up on Matroska as a container as this bug could have disastrous consequences on any hard disc collection over time, as it only rears its head every now and then, and your collection could be ruined unless you have the patience to go through and check every frame of every movie you have converted....

Until this is resolved, I would suggest you stick with VOBs and steer clear of using Matroska for your uncompressed DVDs. I have never seen this bug arise for other types of files so I think its fair to say that Matroska IS safe for other formats... otherwise we would have heard reports of it by now.

[j7n]

The problem in Matroska has been fixed. Unfortunately compatibility with old Matroska tools, such as Gabest's Matroska splitter, has also been broken.



2007-01-11 Moritz Bunkus <moritz@bunkus.org>

* mkvmerge: bug fix: MPEG-1/2 video: The sequence and GOP headers are not removed from the bitstream anymore. This should fix the blockiness if the sequence headers change mid-stream. Fix for Bugzilla bug #167.

This is however irrelevant, as I have found how to use DVDShrink without actually shrinking anything. It can remultiplex needed streams to one big MPEG-2 PS file, plus it keeps the IFOs, so I can reauthor the DVD if I have the need to.