Audio/Video sync issues and an Avisynth script

[VHS-Digital-Buddy]

Hi folks,
I have a recording, and near the beginning there are two parts where the picture gets distorted quite badly, but it recovers for the rest of the video.

I'm running an Avisynth script with VirtualDub 2 to deflicker and clean up the video, however when it hits those parts, and I view the video after processing, the audio and video are out of synch for a few seconds for the rest of the entire video. The video is about 80 minutes long.

Is there a way to fix audio/video synch issues or do I just cut out the bad parts ? Because the rest of the video looks good.

Thanks for any help.

[johnmeyer]

You need to post your script so we can see if there are any operations which might cause the audio to go out of sync. Using something like Deflicker() should not affect sync, but if you change the frame rate then, depending on how that is done, you could lose audio sync.

[jagabo]

Use AudioTrim() to select sections, then append them together to lengthen the audio stream. Then use AudioDub() to join the new lengthened audio to the original video.

[VHS-Digital-Buddy]

Thanks to you both. Will try some things, and revert back if still not successful.

[jagabo]

You can also use Trim() if you prefer to trim the audio by video frames (instead of AudioTrim() which trims by time).

Note that trimming with either may leave audible clicks at the trim points. To avoid these you'll need to overlap parts and use dissolve() to crossfade the audio.

[VHS-Digital-Buddy]

SOLVED:

I had no audio source in my Avisynth script, as previously in VirtualDub2, I went Audio-Audio from other file...

I added the audio source, just below the video source, and works perfectly fine.


Strangely enough, it worked previously on a couple of videos, when I chose the former route. However just glad it works now.

[jagabo]

With some source filters both audio and video will be loaded automatically. Others source filters require separate loads. For example an AVI file opened with AviSource() will get both audio and video. But the same AVI file will require both LWLibavVideoSource() and LWLibavAudioSource() to get both when using LSMASH.

AviSource("filename.avi")
# both video and audio are loaded as "last"

a = LWLibavAudioSource("filename.avi") # a is only the audio
v = LWLibavVideoSource("filename.avi") # v is only the video
AudioDub(v, a) # joins the audio and video together as "last"

[VHS-Digital-Buddy]

Thanks jagabo. Will keep that in mind.