The most lossless way to edit an AVI & export when audio is out of sync?

[Neil-Betamax]

What would be a good way to re-align the audio of my uncompressed AVI captures?

I'd like to do this before I de-interlace and then compress to MP4 as this process is working well for me.

Most of my captures turn out well & in sync, but a fair few have audio sync issues - Betamax for example, so do a lot of DV tapes. I'd like to be able to manually align the audio from the uncompressed AVI whilst retaining as much quality as I can before I export it, de-interlace & compress.

My current process is this:

* VHS S-Video output through Panasonic DMR EX79.
* RCA audio out from VHS into the DMR's Audio in (through a mixer to get audio levels right)
* S-Video & RCA audio out the DMR > into Black Magic Shuttle.
* Black Magic Shuttle into Thinkpad (i7 8th Gen) via USB 3.0.

* Captured with Black Magic Media Express - 625i50 PAL 8bit AVI YUV.
* De-interlaced with AviSynth & the compressed with FFMPEG to MP4.

The audio sync issue is from the master, uncompressed AVI.

I used to edit the audio in Davinci Resolve before exporting to MP4. Now I'm doing it this way using AviSynth & FFMPEG which thanks to some of you on here, I'm getting great results but since it bypasses the need for a video editor, I'm unable to correct the audio sync if it occurs.

any ideas would be great!

Thanks everyone

[Alwyn]

Here's what I do to correct sync in AVISynth:

v=LSMASHVideoSource("File.mp4")
a=LSMASHAudioSource("File.mp4").Normalize(0.98) #Normalise is optional

AudioDub(v,a)
delayaudio(.3) #  Positive is delay, negative is advance in seconds-this example is delay by 0.3 of a second

[themaster1]

I guess the most easy way is to use a NLE, work on the sync and export the audio only . Finally in Vdub you can mux the original video + new audio.

you can also use the audiodelay line in avisynth

avisource(myvideo.avi)
assumetff()
delayaudio(0.5) #0 in milliseconds

[poisondeathray]

Is it a constant delay issue , or a progressively worsening sync issue ?

[videoAI]

try clever FFmpeg-GUI

[Aro]

If You're looking for an easy way to do it, Avidemux has that option (Audio->Choose Track-> Filters->Adjust in milliseconds).

[themaster1]

If You're looking for an easy way to do it, Avidemux has that option (Audio->Choose Track-> Filters->Adjust in milliseconds).

i second that, forgot about good ol' avidemux