how to correct out of sync video/audio in mkv file

[55trucker]

I have an MKV file that will not play cleanly (stutter, audio dropouts) because the h.264 video is out of sync with the DTS audio.
One of the two or both? are to blame? I have the MKVToolnix program to go into the mkv file to extract both video & audio.
If I extract them both I can play the audio portion cleanly with no apparent errors with WMC as it should do.
If I remux just the h264 back into an MKV container on it's own that will play cleanly as well in WMC.
MKVMerge will let me do little adjustments to try to alter the files to try & get them resync'd but it doesn't seem to help.
Is there another more indepth program that can be used to go into the files to try and diagnose them and repair anything to let me put them back together and get them sync'd to each other properly?

[jagabo]

That is more likely a player problem. What player are you using?

[55trucker]

Hi there.
I'm using Windows Media Player Classic-Cinema Series. In the payer I can alter the video output (Overlay mixer, VMR-7-9, renderless) and it makes no improvement to the situation. I've tried adjusting the *stretch* of the audio, adding a small delay as well, went so far as to completely alter the framerate of the video from the stated 23.976 to 30fps which does shorten the overall length of the video (in this case from 149mins to 119mins) and then recalculate how much to stretch the video back again to get the 149mins to see if the proper framerate reappears and it did so. I'm assuming that the problem is moreso with the audio than the video.

[jagabo]

Audio multiplexing/skew problems would be limited to playback from a CD or DVD where seeking is very slow. I'm guessing you mean Media Player Classic Home Cinema, MPCHC. Try changing the source filter and/or the h.264 decoder. View -> Options -> Internal Filters. Change the state of the Matroska source filter and/or the h.264 decoder(s). You have to exit and restart MPCHC for the change to take effect. If you don't have a Directshow MKV splitter or h.264 decoder installed try Haali and ffdshowmt.

[55trucker]

My bad on the player name.
It is MPCHC. I have the full package as supplied with K-lite Codec Pack 666, MPC version 1.5.0.287.
Making changes to the source filters doesn't solve the problem either.
The (original file) audio is almost 3 secs too soon, and suffers from dropouts.
The default install for MPC appears to make use of Haali and that appears in the systray along the ffd filter for AC3 and AC3 filter for DTS passthrough out my soundcard.
This has me scratching my head, as the other mkv files I play don't suffer from the annoyance that this one is displaying.

[jagabo]

Does the problem only happen with DTS track? Does it happen with all DTS tracks? Or is it only this particular video? What if you mux this DTS track with some other video? What if you mux this video with another DTS audio track?

[55trucker]

No, I've many files (HD) that are either DTS or AC3 where audio is concerned, and MPC plays them all with very little fuss. It's just this one. I have tried re-encoding the DTS to AC3 via Audio Converter to see if the problem (if it is the audio) is corrected. At the moment I don't have access to another file of this movie so I can't do a mix&match. What I was looking for is a software program that I can get into the six channel audio file in the same manner that I use Soundforge for editing all of my two channel audio files. I wanted to *see* the wav, Soundforge (at least the version I own) doesn't recognize 4,5, or 6 channel audio.

[jagabo]

You don't have to have matching audio to run a test. Just mux the video with any other DTS audio and see if you have stuttering problems. And mux the audio with any other h.264 video file and see if that has stuttering problems. That may isolate the problem to either the audio or the video.

If you are getting stuttering it has nothing to do with whether the audio is in sync or not. The player doesn't know if the audio is in sync with the video. It just plays audio along with the video. Audio doesn't have to start at the same time as the video and the two tracks don't have to be the same length. The player is having some kind of problem playing either the video or the audio. In all likelihood the MKV reader/splitter is having trouble communicating with the audio or video decoder.

[55trucker]

You've suggested something that did not occur to me. I did as you suggested.....took two different movies and did a swap in both directions for both video & audio. When I paired this troubled movie's audio with another movie's video they played cleanly. But, when I paired the the troubled movie's video with the other clean audio the movie would not play properly. The audio would stutter as it happened with the original troubled file. So, now I know that the vid is the problem. Thx for the assistance......now I wonder what if possible I can do to correct this situation.

[jagabo]

Hopefully you won't have to reencode the video.

[55trucker]

Well, my inexperience with h.264 is showing thru.... If I extract the video from the mkv container and attempt to just play the 264 file in MPC I cannot play it at all. No matter what output setting I choose (overlay, VMR 7, VMR 9, NULL) MPC cannot/will not render the file so as to play it. So when the two parts of the file are together MPC is renderring the audio and properly playing that but the video is *just going along for the ride.* Now I was under the impression that if the video (like the audio) is encoded properly they should both be capable of playing outside of the MKV container, and I am not getting that with this video. Now, assuming the file is corrupt, in it's present form would I use something such as MEGUI to go into it and restructure the file hoping that any error can be corrected?

[jagabo]

You demux the video to an h.264 elementary stream? I wouldn't count on many players to play that. You might try muxing the audio and video into an MP4 file. See if that works any better.

[poisondeathray]

Try tsmuxer and .m2ts transport stream, because you will have problems with DTS in .mp4 container

Try other players, non directshow, like VLC or SMPlayer

or try older MKVToolNix version to re-wrap . Something like 3.2.0 or 4.0.0 are know to be very stable

[jagabo]

you will have problems with DTS in .mp4 container

Ah, yes. Forgot about that.

[55trucker]

Well, after getting nowhere with what I had, my nephew sent me another file of the movie. This time he sent it as an M2TS file AVCHD (compressed). The gods must not like me, it won't play either. I took poisondeathray's suggestion and removed all of the k-lite codec pack I had and went back to an older version of just MPC (1.4.2499) and just for good measure I also installed net framework 3.5 just to get the EVR codecs option and both of the files sent to me will not play properly in any of the available output options. I did try remuxing the first into an m2ts file and it improved nothing. So, either the source disc must be corrupt? or something went wrong with the original encoding of the movie, but it seems I can go no further with this.

[poisondeathray]

mpc is directshow player . I said non directshow player, like vlc or smplayer

The reason for this is to test if it's a problem with directshow filters, splitters etc.... VLC doesn't rely on system installed filters, it runs independently and self contained

If it plays cleanly in vlc, then you've narrowed down the problem . If the same issues occur , then it might be problem with source

Does this recent file play ok on your nephew's system? If it does, that points to the problem being your directshow setup.

[jagabo]

the source disc must be corrupt?

Copy the file from the disc to your hard drive. If you don't get errors during the copy the disc is fine.

[55trucker]

Unfortunately I don't own a Bluray rom drive to actually rip to my hard drive, so I have an outside source to do so. I've tried VLC in the past and when it comes to anything else other than a 1080p or 720p file it runs flawlessly, but these hd files cause it to have an absolute heart attack when attempting to play. Now, my system is an older P4, but it IS a big P4...3.5gig, 4 gig of ram, my graphics card is an HDMI 1 gig ATI card, and I'm still using XP SP3, it still to my mind is a useful system as it doesn't hog power as Vista does/did and as the moment I haven't considered upgrading to 7 as I don't know if there would be any real benefit. Puzzled to say the least.

[jagabo]

A single core P4 (even with Hyperthreading) can't play 1080p h.264 video smoothly unless you have a graphic card with GPU h.264 decoding and are using a player that supports DXVA.

[55trucker]

Well the VLC version I have at the moment is.......1.1.7 (win32)......I'm pretty sure that is the latest version?

[55trucker]

A single core P4 (even with Hyperthreading) can't play 1080p h.264 video smoothly unless you have a graphic card with GPU h.264 decoding and are using a player that supports DXVA.

This ATI card makes use of what they refer to as AVIVO HD. It is supposed to allow playing of h.264 content (among others) and it has up to now been pretty much reliable. As for the DXVA, I was under the impression that MPC does that.

[jagabo]

DXVA (DirectX Video Acceleration) is what Microsoft calls the interface that allows graphics cards to perform hardware h.264 decoding (amongst other things). VLC didn't support DXVA until recently. MPCHC supports DXVA but you may have to enable it. View -> Options -> Internal Filters -> Transform Filters -> H.264/AVC (DXVA).

All the parts have to be available: DXVA (started with DX 9, I think), a player that supports DXVA, and a graphics card that supports DXVA. If you can play other 1080p24 or 1080p30 videos smoothly you probably have everything. Note that DXVA doesn't support all possible h.264 features.

[55trucker]

You possibly can't imagine how frustrating this can be (perhaps you can if you've encountered this as well) LOL....it may be something so simple as an adjustment to the MPC players settings, but one doesn't quite know just what to adjust. I did come across this tutorial that someone out there went to the trouble of putting together (I think it is a blog). I basically followed this (except for blocking the filters section because those ffd filters do not display at all) outline as it mentions XP SP3, my series of graphics card, etc etc, and still can't get this file to play. My graphics card is set to display the HDMI output at 1920x1080p@24hz going to my 46" TV (extended), everything to my 21" primary monitor is system default. http://imouto.my/watching-h264-videos-using-dxva/

[jagabo]

If you want to post a sample I'll take a look at it. Or try opening it with MediaInfo and posting what that program has to say about the video. Especially the "Encoding Settings".

[dylz]

I didn't really read the post but most audio sync issues are with outdated or conflicting codecs the one way to check is use a player that uses it's own codecs like vlc or the preview in vdub or avidemux. Remuxing can sometimes help aswell.

When there seperated h.264 and dts audio did you open file h.264 and dub the dts ?

[55trucker]

If you want to post a sample I'll take a look at it. Or try opening it with MediaInfo and posting what that program has to say about the video. Especially the "Encoding Settings".

If I were to post a *sample*....how large can I allow? A 10 min segment is approx. 900mb large. 1 min is going to be roughly 90mb. ^Dubbing the audio while playing the h.264 stream? Didn't realize that one can actually do that.

[55trucker]

Here's the mediainfo on just the sample I created



General
ID : 1
Complete name : I:\a Time to Kill\A Time to Kill 1080p BluRay AC3 edited cut.m2ts
Format : MPEG-TS
File size : 906 MiB
Duration : 9mn 58s
Overall bit rate : 12.7 Mbps

Video
ID : 4113 (0x1011)
Menu ID : 1 (0x1)
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 8 frames
Duration : 9mn 58s
Bit rate mode : Variable
Bit rate : 11.0 Mbps
Maximum bit rate : 40.0 Mbps
Width : 1 920 pixels
Height : 804 pixels
Display aspect ratio : 2.35:1
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.298
Stream size : 815 MiB (90%)
Writing library : x264 core 66 r1112M f43e22a

Audio
ID : 4352 (0x1100)
Menu ID : 1 (0x1)
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Duration : 9mn 58s
Bit rate mode : Constant
Bit rate : 640 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Stream size : 45.6 MiB (5%)
Language : English

[jagabo]

8 reference frames (ReFrames) may be too much for DXVA and 1080p video. But I wouldn't expect the encoder to have used 8 reference frames very often. And I would only expect playback to have problems when it did.

The encoder didn't include the settings it used as metadata so MediaInfo doesn't report it. So we don't know how many consecutive B frames the video uses. That can be another source of problems for DXVA. The other settings we can see look pretty normal. You may have to reencode the video.

[55trucker]

Yeah.....I was under the impression that reframes should not exceed 4? This is the entire mediainfo text

[55trucker]

As I write this I'm attempting to completely remux the entire file with Mediacoder. I don't know if it will have any benefit, but I'm hoping that the program can alter the reframes situation that jagabo mentioned. Seeing as all of my other mkv files have a respectable reframes setting of 5 or less maybe this will work. Does anyone know for certain if the h.264 file once created can be recreated to alter the reframes? I was lead to believe that the reframes of the file can't be changed once established.
So one has to start all over again beginning the process at the copying of the disc.