AVC MP4 Sync Drifts in Editing Programs, is Fine in Playback Programs

[koberulz]

General
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 7.33 GiB
Duration                                 : 3 h 59 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 4 387 kb/s
Tagged date                              : UTC 2018-11-26 13:49:55
Writing application                      : Lavf56.19.101

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 3 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 3 h 59 min
Bit rate mode                            : Variable
Bit rate                                 : 4 284 kb/s
Maximum bit rate                         : 5 500 kb/s
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 29.772 FPS
Minimum frame rate                       : 14.983 FPS
Maximum frame rate                       : 29.970 FPS
Original frame rate                      : 29.970 (30000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.156
Stream size                              : 7.15 GiB (98%)

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 3 h 59 min
Bit rate mode                            : Variable
Bit rate                                 : 92.8 kb/s
Maximum bit rate                         : 99.8 kb/s
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 spf)
Compression mode                         : Lossy
Stream size                              : 159 MiB (2%)
Default                                  : Yes
Alternate group                          : 1

Text
ID                                       : 1-CC1
Format                                   : EIA-608
Muxing mode                              : SCTE 128 / DTVCC Transport
Muxing mode, more info                   : Muxed in Video #1
Duration                                 : 3 h 59 min
Bit rate mode                            : Constant
Stream size                              : 0.00 Byte (0%)
Encoded stream size                      : 0.00 Byte (0%)
CaptionServiceName                       : CC1

I have other identical files, which all work fine. This one drifts, with the audio finishing a couple of minutes before the video in Audacity, Audition, and Premiere. Plays fine and in-sync in VLC and PowerDVD.

[poisondeathray]

Frame rate mode : Variable
Frame rate : 29.772 FPS
Minimum frame rate : 14.983 FPS
Maximum frame rate : 29.970 FPS
Original frame rate : 29.970 (30000/1001) FPS

Look up "VFR" . Variable frame rate. It's discussed often

Basically you'd have to convert to CFR to edit it.

You're missing video frames. Video is shorter than audio , this causes the drift. In a media player, timecodes keep it in sync by displaying certain frames longer than usual. In a CFR version, there would be duplicate "placeholder" frames instead at those spots

[koberulz]

WTF? All the others are CFR, I have no idea why this one is VFR.

*sigh*

[koberulz]

Okay, looks like one other is also VFR, but it works fine in PP. Weird.

How do I convert this one so it co-operates?

Also I'm not sure I am missing video frames, as the audio always finishes early which implies added frames, not absent ones does it not?

[poisondeathray]

Okay, looks like one other is also VFR, but it works fine in PP. Weird.

How do I convert this one so it co-operates?

Also I'm not sure I am missing video frames, as the audio always finishes early which implies added frames, not absent ones does it not?

If it's minimally variable, or just minor jitter in the timecodes, then you might not detect a sync issue . These aren't truly VFR, and can be treated as CFR. You might be able to remux it and fix those

Ones that have larger variations, will produce a sync issue for sure in PP or any editor

Newer versions of PP handle VFR slightly better

If the "assumed" CFR frame rate in PP is below the actual average framerate, the video might be longer. If the "assumed" CFR frame rate in PP is above, the video might be shorter. But it in both cases, they will still be in/out of sync in sections if you don't have one of the minimally variable cases

You can do the math. Look at the framecount and calculate the duration based on a FPS. 99% of timecode VFR cases will have missing frames



Use search, it's discussed often. Search for "VFR to CFR". There are several methods, several variations,none of them perfect, but it will be better than what you have now. For example, you can use avisynth to convert to CFR

DirectShowSource("video.mp4", fps=29.97, convertfps=true)

[koberulz]

It's still out of sync after doing that.

[poisondeathray]

Was the output file in sync in a media player? What format did you use, what does mediainfo say ?

The minimally variable ones where you can just assume CFR, usually have min/max like 29.95, 29.98 or something (ie. very little deviation, just jitter). But you have min 14.983 . But it might work , you can use mp4fpsmod to patch it to CFR. But I doubt it will work for that one, because it really is variable

[koberulz]

I just told PP to interpret as 29.97 instead of 29.77, worked out how long that made it, reset it to original, and then used the rate stretch tool on the video. It's now synced at both ends, fingers crossed it's functional across the bit I need (which is only about 30-40 minutes of the four hours).