Audio Files Muxing - Sync Problems

[blazzer12]

HI,

I have two files, lets say a.mkv[H264+AC3:720p, 24fps] and b.mkv[MPEG2+AC3:420p, 29.97fps].

Both files are the same movie, but different languages. They are just dubbing. Have a duration difference of around 1 second.

So, I figured I would adjust the 1 second sync problem and mux the audio file in b.mkv into a.mkv but got a sync problem.
-----the audio is starting correctly and ending correctly, at the exact seconds. But there is no sync. How to make sense of it?

Is there a way to sync them properly?

-------------FILE INFO-------------
I should have done this in the beginning itself. Sorry for not providing full details earlier. I didn't think the problem would take all this info in to account.

>>>>>>a.mkv<<<<<<

Format : Matroska
Format version : Version 2
File size : 3.00 GiB
Duration : 2h 25mn
Overall bit rate : 2 959 Kbps
Encoded date : UTC 2012-05-08 04:01:40
Writing application : mkvmerge v5.2.1 ('A Far Off Place') built on Jan 2 2012 23:21:10
Writing library : libebml v1.2.3 + libmatroska v1.3.0

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.2
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 2h 25mn
Bit rate : 2 317 Kbps
Width : 1 280 pixels
Height : 544 pixels
Display aspect ratio : 2.35:1
Frame rate mode : Constant
Frame rate : 24.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.139
Stream size : 2.29 GiB (76%)
Writing library : x264 core 120 r2164

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : A_AC3
Duration : 2h 25mn
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
Compression mode : Lossy
Stream size : 664 MiB (22%)
Language : Hindi
Default : Yes
Forced : No

>>>>>>b.mkv<<<<<<

Format : Matroska
Format version : Version 2
File size : 3.42 GiB
Duration : 2h 25mn
Overall bit rate : 3 375 Kbps
Encoded date : UTC 2013-01-04 11:21:06
Writing application : MakeMKV v1.7.10 win(x86-release)
Writing library : libmakemkv v1.7.10 (1.2.0/1.1.0) win(x86-release)

Video
ID : 1
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings, BVOP : No
Format settings, Matrix : Custom
Codec ID : V_MPEG2
Codec ID/Info : MPEG 1 or 2 Video
Duration : 2h 25mn
Bit rate : 2 860 Kbps
Width : 720 pixels
Height : 480 pixels
Display aspect ratio : 16:9
Original display aspect ratio : 2.40:1
Frame rate mode : Constant
Frame rate : 29.970 fps
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Scan order : Top Field First
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.276
Stream size : 2.90 GiB (85%)
Language : English
Default : No
Forced : No
Color primaries : BT.601 NTSC
Transfer characteristics : BT.601
Matrix coefficients : BT.601

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : A_AC3
Duration : 2h 25mn
Bit rate mode : Constant
Bit rate : 448 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 465 MiB (13%)
Title : 3/2+1
Language : Telugu
Default : Yes
Forced : No

Text
ID : 3
Format : VobSub
Codec ID : S_VOBSUB
Codec ID/Info : The same subtitle format used on DVDs
Language : English
Default : Yes
Forced : No

[Cornucopia]

Multitrack Audio Editor/DAW put both in parallel tracks, adjust one to the other, by sound or visually by waveform. Won't every exactly sync because of language cadence differences, but might could sync during the interim music and the rest should flow.

However,
1 + 2 + 1 + 2 + 3 + 2 + 1 + 2 + 1 = 15
and
1 + 2 + 3 + 4 + 5 = 15

They may start and end at the same spot (or very nearly), but if the cuts are different, there is NOTHING you could do to get them in sync.

Scott

[blazzer12]

They may start and end at the same spot (or very nearly), but if the cuts are different, there is NOTHING you could do to get them in sync.

Sorry for the n00b question, but what are cuts?
If your are referring to the videos, they are the same. No extra or missing scenes or chapters.

[El Heggunte]

@ blazzer12:

Your problem still is defined "too vaguely".
Which file has audio with duration of "+1 second", a.mkv or b.mkv ?
Also, how did you "adjust" the audio of b.mkv ? By specifying a fixed delay (which can have a negative value) in the Matroska muxer, OR by changing its duration plus a re-encode ?

[hello_hello]

[
Sorry for the n00b question, but what are cuts?
If your are referring to the videos, they are the same. No extra or missing scenes or chapters.

You might be surprised. I've seen two versions of a video where there's one less frame between scene changes here, a couple there, and it makes it impossible to sync the audio even though the videos appear the same.

"Assuming" the 29.97 fps version isn't interlaced video and it's been converted from film, when the conversion process (it's call telecine) is reversed you'll be left with the original film and therefore the audio should match, but..... for NTSC it's run at 23.976fps, not 24fps. So in order to match the audio from the NTSC version it's likely you'll need to change the framerate of the 720p version to 23.976fps.

[JetrellFo69]

It may also be possible that the audio is for 2 different versions of the same movie. Like the difference between a theatrical and extended cut. It's just something to consider. I would agree with hello on the frame rate issue. You may have to learn a few things to get your issue fixed but most of it is fairly easy to do once you understand the how & why.

[blazzer12]

@ blazzer12:

Your problem still is defined "too vaguely".
Which file has audio with duration of "+1 second", a.mkv or b.mkv ?
Also, how did you "adjust" the audio of b.mkv ? By specifying a fixed delay (which can have a negative value) in the Matroska muxer, OR by changing its duration plus a re-encode ?

1) b.mkv is +1 longer than a.mkv
2) I have to mix audio in b.mkv to a.mkv, so I put '-1' delay to audio file in b.mkv when muxing. Also tried '+1' delay. But no result.

[blazzer12]

It may also be possible that the audio is for 2 different versions of the same movie. Like the difference between a theatrical and extended cut. It's just something to consider. I would agree with hello on the frame rate issue. You may have to learn a few things to get your issue fixed but most of it is fairly easy to do once you understand the how & why.

I am sure about the video not being two different versions. They are just audio dubbing.

[blazzer12]

[
Sorry for the n00b question, but what are cuts?
If your are referring to the videos, they are the same. No extra or missing scenes or chapters.

You might be surprised. I've seen two versions of a video where there's one less frame between scene changes here, a couple there, and it makes it impossible to sync the audio even though the videos appear the same.

"Assuming" the 29.97 fps version isn't interlaced video and it's been converted from film, when the conversion process (it's call telecine) is reversed you'll be left with the original film and therefore the audio should match, but..... for NTSC it's run at 23.976fps, not 24fps. So in order to match the audio from the NTSC version it's likely you'll need to change the framerate of the 720p version to 23.976fps.

From the media info, both the files seem to me progressive. a.mkv is a bluray rip. b.mkv is from a DVD5 made using makeMKV.

Do you want me to re-encode a.mkv to 23.976 fps? I fear that might mess with the quality of the video. Can I re-encode b.mkv to 24 fps so I can simple extract audio and mux to a.mkv?

[manono]

Do you want me to re-encode a.mkv to 23.976 fps?

That should have been done to begin with. That's what you get for downloading garbage from the internet. Assuming it's really progressive as you said, it was deinterlaced in one of two ways - either every 5th frame is a duplicate or 2 of every 5 frames are blended during movement. If you can pause it and advance a frame at a time you'll see.

As hello_hello said earlier, one problem is the two different framerates. 24fps and 29.97fps (which should really be 23.976fps). However, the overall difference in lengths should be something like 8-9 seconds. So there are other differences between the two as well. Are you sure the total frame count is exactly the same? I'd bet it isn't. And 2 hours 25 minutes isn't really precise enough.

This would be difficult to synch even if you knew what you were doing. Since you don't...

[hello_hello]

Do you want me to re-encode a.mkv to 23.976 fps? I fear that might mess with the quality of the video. Can I re-encode b.mkv to 24 fps so I can simple extract audio and mux to a.mkv?

You don't need to re-encode it. You can open the MKV using MKVMergeGUI and select the video stream, specify a new frame rate under the "format specific options" tab and re-save it as a new MKV. Of course you can also add the second MKV and de-select it's video stream in order to add the audio from it at the same time (while applying any delay to the audio you think might be necessary etc). Sorry, I figured given you were asking about remuxing MKVs while switching audio streams you'd be familiar with doing so.

You might get lucky and find by changing the frame rate and/or applying an appropriate audio delay they'll match up, but it's just as likely they won't.

Sometimes when I've wanted to add audio from a different version of what appears to be the same video, I've found even adjusting the frame rate by a tiny amount can do it.... or at least get it close enough..... say trying 23.975fps instead of 23.976fps etc (I think MKVMergeGUI will even accept more specific frame rates such as 23.9755).... but it pretty much relies on each version of the video being cut the same way and the movie itself having an identical number of frames or they'll probably never match up no matter what you do.

A couple of times I've found there's only one or two places where the audio sync changes, so I've split the MKV into sections, adjusted the audio sync for each while remuxing them, then joined the sections together again, but depending on how you need to adjust the audio delay, even that can leave you with little audio gaps to keep it in sync.

And I remember one instance where the MKVs I was working with appeared to have a constant frame rate, but there must have been duplicate frames throughout.... or frames here and there which had twice the normal frame duration..... because as soon as I specified a frame rate when remuxing, even when I specified the original frame rate, the remuxed MKV would have a different duration to the original. Not that it's likely that'd be a problem, but it's something else which can make matching audio and video a bit of a challenge.