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I have an MKV file that has an issue with the audio - it subtly lags behind the video. They start in sync, and then over the course of the whole clip they drift out of sync.

My first idea was that the video framerate is specified wrong by 1, but a quick calculation shows that the effect would be MUCH more pronounced then. I'm at a loss how this could have happened, and better yet - how do I correct it now, since I don't have access to the original source from which it was encoded anymore? Here's the output from MediaInfo:

General
Unique ID                                : [Redacted]
Complete name                            : [Redacted]
Format                                   : Matroska
Format version                           : Version 4
File size                                : 823 MiB
Duration                                 : 22 min 17 s
Overall bit rate                         : 5 164 kb/s
Encoded date                             : UTC 2017-10-16 18:54:58
Writing application                      : mkvmerge v17.0.0 ('Be Ur Friend') 64-bit
Writing library                          : libebml v1.3.5 + libmatroska v1.4.8

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings                          : CABAC / 2 Ref Frames
Format settings, CABAC                   : Yes
Format settings, RefFrames               : 2 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 22 min 14 s
Bit rate                                 : 4 920 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
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)                       : 0.099
Stream size                              : 772 MiB (94%)
Writing library                          : x264 core 115 r1995M 5a37283
Encoding settings                        : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=2 / psy=1 / psy_rd=1.00:0.00 
                                           / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 
                                           / chroma_qp_offset=0 / threads=4 / sliced_threads=0 / nr=250 / decimate=1 / interlaced=0 / bluray_compat=0 
                                           / constrained_intra=0 / bframes=0 / weightp=1 / keyint=250 / keyint_min=24 / scenecut=40 / intra_refresh=0 
                                           / rc_lookahead=10 / rc=2pass / mbtree=1 / bitrate=4920 / ratetol=1.0 / qcomp=0.60 / qpmin=5 / qpmax=69 
                                           / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=1:1.00
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio #1
ID                                       : 2
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Codec ID                                 : A_AC3
Duration                                 : 22 min 17 s
Bit rate mode                            : Constant
Bit rate                                 : 192 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 30.6 MiB (4%)
Language                                 : Russian
Service kind                             : Complete Main
Default                                  : Yes
Forced                                   : No

Audio #2
ID                                       : 3
Format                                   : AAC LC SBR
Format/Info                              : Advanced Audio Codec Low Complexity with Spectral Band Replication
Commercial name                          : HE-AAC
Format settings                          : Explicit
Codec ID                                 : A_AAC-2
Duration                                 : 22 min 16 s
Bit rate                                 : 127 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 23.438 FPS (2048 SPF)
Compression mode                         : Lossy
Stream size                              : 20.2 MiB (2%)
Language                                 : English
Default                                  : No
Forced                                   : No

As you can see, the video is 22:14 long, while the sound is 22:17 long. Thus over the course of 22 minutes the sound drifts 3 seconds out of sync. To correct that in the framerate, the video would need to be played at about 24.054fps, but that's not any standard framerate I know of.

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