NTSC DVDs out of sync

[chrisclarke]

I've noticed a couple of NTSC DVDs rips we've used recently to make clips from have been out of sync in DCP-o-Matic and resulting DCPs. These are ripped using MakeMKV and playback in sync on other players.

Setting Override detected video framerate to 23.976 (from 29.97) in advance settings will put the video and sound back in sync.

Copying below the mediainfo output for one of the files:

Complete name :
Format : Matroska
Format version : Version 2
File size : 6.68 GiB
Duration : 2 h 9 min
Overall bit rate mode : Variable
Overall bit rate : 7 402 kb/s
Encoded date : UTC 2023-02-09 14:14:00
Writing application : MakeMKV v1.17.2 win(x64-release)
Writing library : libmakemkv v1.17.2 (1.3.10/1.5.2) win(x64-release)

Video
ID : 1
ID in the original source medium : 224 (0xE0)
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings : CustomMatrix / BVOP
Format settings, BVOP : Yes
Format settings, Matrix : Custom
Format settings, GOP : M=3, N=12
Codec ID : V_MPEG2
Codec ID/Info : MPEG 1 or 2 Video
Duration : 2 h 9 min
Bit rate mode : Variable
Bit rate : 7 199 kb/s
Maximum bit rate : 9 800 kb/s
Width : 720 pixels
Height : 480 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 23.976 (23976/1000) FPS
Original frame rate : 29.970 (30000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.869
Stream size : 6.49 GiB (97%)
Language : English
Default : No
Forced : No
Original source medium : DVD-Video

Audio
ID : 2
ID in the original source medium : 189 (0xBD)128 (0x80)
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Format settings : Dolby Surround
Codec ID : A_AC3
Duration : 2 h 9 min
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)
Compression mode : Lossy
Stream size : 177 MiB (3%)
Title : Stereo
Language : English
Service kind : Complete Main
Default : Yes
Forced : No
Original source medium : DVD-Video

Text
ID : 3
ID in the original source medium : 189 (0xBD)32 (0x20)
Format : VobSub
Codec ID : S_VOBSUB
Codec ID/Info : Picture based subtitle format used on DVDs
Duration : 2 h 8 min
Bit rate : 5 979 b/s
Count of elements : 2545
Stream size : 5.50 MiB (0%)
Language : English
Default : Yes
Forced : No
Original source medium : DVD-Video

[Carsten]

How did you previously create DCPs from these 29,97fps sources? 30fps?

Audio and video sync recently had some fixes to accommodate for strange codec variations. Which version of DCP-o-matic did you use previously, and did you update recently?

[chrisclarke]

I'm seeing this on both 2.16.42 on a PC and 2.16.32 on a PC. Yes would usually just let DCP-o-Matic handle a 29.97>30fps for anything from NTSC.

These are both originally shot of film and have this line in mediainfo which made me curious:

Frame rate : 23.976 (23976/1000) FPS
Original frame rate : 29.970 (30000/1001) FPS

[carl]

I guess these files are encoded using "soft telecine" i.e. the actual file is 23.976 or 24fps but it has markers to say that it should be played back at 29.97fps and that the player should handle the pull-down.

DCP-o-matic is supposed to spot this and run the content at 23.976 (as you have forced it to do with your setting).

It would be interesting to see the "log" file from one of the projects where this is going wrong.

[Carsten]

'soft telecine'. The codec torture never stops. What else will they come up with? A video file trying to emulate a cigarette?

[carl]

It is an endless source of mystery and wonder indeed.

[jdent02]

'soft telecine'. The codec torture never stops. What else will they come up with? A video file trying to emulate a cigarette?

This is how most commercial NTSC DVD's encoded from 24fps film have been done since the dawn of time. Saves them having to encode a dedicated 29.97fps version (and a 25fps version for PAL).