AVI audio unsyncs when compressed to MP4?
 

I really want to know what I'm doing wrong before proceeding with any other VHS transfers.

1. After capturing with virutaldub 1.9, I check through an uncompressed 4 hour avi and I see/hear a correct sync throughout the entire video - 10 minutes from the end, everything matches up.

So next I apply avisynth preferences and compress the video to mp4 in virtualdub 2. The final version's sync starts out ok but gradually gets worse and worse as the video progresses. Why doesn't the mp4 maintain the sync from the uncompressed avi?

Specifics on my settings are listed here:
https://www.digitalfaq.com/forum/vid...e-between.html

2. Are there "best" timing options in virtualdub for those who wish to separately capture audio from a different VCR with audacity? In other words, are there timing options that eliminate the "slowed down" or "sped up" audio moments, assuming all gear is functioning correctly?

2.1 Related, what is the preferred file format and compression when saving VHS audio in audacity? And is there a "best" practice for replacing audio?

Currently I use "audio from another file..." and apply the same compression settings I would normally use, but I notice this often results in an mp4 size that seems unnecessarily larger than it should be.

3. In avisynth I'm sometimes stuck editing a video using "FFMPEGSource("1.avi") + FFMPEGSource("2.avi") + etc" combined with "Trim(x,x) + Trim(x,x) + etc" -- especially if there's an audio issue or other mistakes in the later half of a transfer.

I'm wondering why every time there's a new Trim(x,x) added into the chain, it delays the audio more and more (usually adding around 1/10th second of audio), making it even harder for me to sync everything afterwards. A few times I've fixed the sync by adding redundant frames until the sync matches, but I hate doing this not only because it's annoying to fix but also because it ruins the flow of the edit.

I appreciate any help I can get! Thanks everyone

I capture to HuffYUV, not uncompressed. It's lossless compression so it saves disk space and reduces processing time.

From AviSynth, I output to HuffYUV and compress later in Handbrake.

From the AviSynth output file, I export the audio to lossless FLAC and import that into Audacity.

I use MKVToolNix GUI for the final multiplex because it makes it easy to add chapter stops and other features.

I use AviSource(), not FFMPEGSource().

Mostly same as traal for me.
But I do
- WAV, not FLAC (because WAV processes faster in Sound Forge)
- Hybrid, never Handbrake (very inferior)

Never uncompressed capture.

For problems with fast/slow (pitched high/low) audio from capture in VirtualDub, it's a mere timing setting issue. Disable speed up/down, and enable the middle "integrated audio/video". I forgot the exact test off-hand, not at video computer at this moment.

Thanks for this tip! I haven't noticed any unsyncing yet since capturing to HuffYUV, and the avi index files are auto-created a lot faster.

I tried this and it gave me a "line 2 error" or something similar. I'm going to play around with the code to see if I can get it working.
Reading into this now - I'm seeing AviSource might join separate videos together more easily than FFMPEGSource.

This is my first time hearing of Hybrid. Is it used for the final step? (deinterlaced/compressed mp4 render)?

-- merged --

I spoke too soon. I may need to change the code to Avisource but I'm getting "couldn't locate decompressor for fourcc FFVH"

There's lots of different info about this error with different codecs but i can't find the solution for FFVH.

- Handbrake is like McDonald's. or any fast food joint.
- Hybrid is like Applebee's, or any sit-down restaurant. Slightly more involved than talking into the clown head, but the quality you get is vastly better.

Hybrid is a complex GUI that both encodes and filters. So, for example, you can QTGMC, set some NR, and encode the lossless source to x264.

FFVH is not the official Huffyuv, but the "FFMPEG Huffyuv" variant with issues.
- Use VirtualDub, not VirtualDub2
- Install Huffyuv from Github, as linked here: https://www.digitalfaq.com/forum/vid...html#post94709 -- and linked there instead of direct, as that thread has some common install mistakes discussed.

Uncompressed is I/O heavy, and can cause dropped frames for that reason. If you don't have VirtualDub set correctly, bad timing settings, you can drop without being logged. Not good. So we probably should verify VirtualDub and timing settings too.

I downloaded Hybrid last week. I'm ready to get into it but a little overwhelmed by the number of tabs and options. I'll search around for tutorials asap.

I used Vdub2 for my last few transfers only because my copy of Vdub1.9 is missing any options for compression. Compressing to huffyuv on VDub2 is keeping some videos sync'd but not all. So I'll try installing huffyuv again in a way that adds the codec to 1.9.

Also as per your earlier response, I've been using the 2nd timing option, which drops lots of frames. After I switched back to the 3rd timing option with the audio resampling, the syncs were aligned a lot more often. Trying to figure out how to access the log after transferring.