Audio/video de-sync (sometimes after scrubbing)

[FranzLiebkind0]

So I have a .mov file I has captured many years ago using a cheap capture device (iGrabber) and their propriety capture software. The original .mov file is a VHS source and is interlaced - it is also apparently 29.7 frames/sec (not 29.97) according to Windows file properties. The original .mov file does not have video/audio sync issues

I initially tried Handbrake with yadif de-interlacer which resulted in a de-interlaced product without audio sync issues. I do however wish to use QTGMC instead as the samples I tried with the same file looked a bit better

I already have a little experience with avisynth+/virtualdub for .avi files I captured with successful h264/QTGMC processing (I've only been learning video processing for last month or two)

I am having trouble doing the same with this file (and unfortunately I have thrown away the source VHS cassette). No matter what I try the audio seems to de-sync. Interestingly, in VLC it sometimes is synced for some period of time but then is de-synced after scrubbing. Re-starting the video, the same spot that seemed in sync originally is now out-of-sync again. Would appreciate any help with this!

My avisynth script - the reason I am not using LSMASHAudioSource (vs LWLibavAudioSource) is because the former would only capture a buzzing sound instead of audio (even when I tried different tracks)

SetFilterMTMode ("QTGMC", 2)
a=LSMASHVideoSource(source="I:\VHS source\video.mov", track=0, threads=0, seek_mode=0, seek_threshold=10, dr=False, format="")
b=LWLibavAudioSource("I:\VHS source\video.mov")
audiodub(a,b)
AssumeTFF()
AssumeFPS(29.70, sync_audio=true)
QTGMC(preset="Slower", EdiThreads=3)
Spline64Resize(640,480)
Prefetch(10)

Thanks

[jagabo]

Try specifying the frame rate in LSMASHVideoSource(..., fpsnum=29700, fpsden=1000), or 30000 and 1001.

[FranzLiebkind0]

That was it - thank you so much!!