Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Help Fixing drift when syncing audio
#1
I want to sync an audio track from a VCD to a DVD. Both are 25fps.

The duration is near indentical except the VCD audio has a longer intro. Taking this into account there is about a minute difference.

If I sync the beginning of the movie, the VCD audio drifts and falls behind the DVD one.

I’m not sure this is due to PAL/NTSC since both are seemingly PAL 25fps, but there is obviously a speed difference.

Any tips on how I would go about syncing?
Reply
Thanks given by:
#2
Probably you have checked this, but... maybe there is some missing frames in one (or both); it happens sometimes, especially at reel change (every 20m or so); try to check sync every, let's say, five minutes; if they are in sync in a step, and not in the next one, a missing frame (with related missing audio) should be there!
Reply
Thanks given by:
#3
I've synced quite a few LDs now and the drifting is very common with both digital and analog tracks. There are two basic ways to sync, one is by matching video frames, and the other is by matching waveforms. I'm not able to capture video at the moment, so I do waveform matching with Cockos Reaper. You basically drop both mixes into separate channels, line them up at the beginning, and then play it. When it starts to drift from your reference track and you hear echoing you split the track and readjust it to match back up. It can vary wildly between titles, like I just synced Summer Rental and it never drifted more than 5ms every few minutes, but now I'm syncing Return of the Living Dead 2 and it drifts like crazy every 30 sec (not to mention missing frames or extra frames where you will have to cut out or patch in audio). It's not impossible to sync, it just takes way more time since you need more splice points.
Reply
Thanks given by:
#4
Yeah I’ve had to fix missing frame and minor drifting before. I’m doing exactly as you say and matching waveforms using Audacity.

But for this particular movie, within a few minutes it’s alreasy drifting by a second or two. That sounds like more than missing frame right?

I even tried converting the audio as if it was NTSC -> PAL but that makes it too fast.

I was reading about sample rates. DVDs use 48KHz while VCDs use 44.1KHz. Would resampling effect speed and pitch?
Reply
Thanks given by:
#5
If its a different master its definitely possible. I've noticed at the end of shots they will sometimes cut a few frames between masters, which can mean going off track pretty quickly. The sampling rate shouldn't effect it that much, both rates are based on the amount of samples in one second of time. A higher sampling rate will allow higher frequencies to be captured, but it won't change the actual pitch of the sound.
Reply
Thanks given by:
#6
(2019-02-15, 06:44 AM)bronan Wrote: I've synced quite a few LDs now and the drifting is very common with both digital and analog tracks. There are two basic ways to sync, one is by matching video frames, and the other is by matching waveforms. I'm not able to capture video at the moment, so I do waveform matching with Cockos Reaper. You basically drop both mixes into separate channels, line them up at the beginning, and then play it. When it starts to drift from your reference track and you hear echoing you split the track and readjust it to match back up. It can vary wildly between titles, like I just synced Summer Rental and it never drifted more than 5ms every few minutes, but now I'm syncing Return of the Living Dead 2 and it drifts like crazy every 30 sec (not to mention missing frames or extra frames where you will have to cut out or patch in audio). It's not impossible to sync, it just takes way more time since you need more splice points.

I've had that problem many times also. It's why I still haven't finish Dawn of the Dead. I was half way through the movie with 200 edits and it wasn't PAL or time compressed. Very tedious work.
New members: Please do not post or PM asking where to get something. Projects are for long term, participating members only. Stick around and make some friends
Reply
Thanks given by:
#7
(2019-02-15, 06:40 PM)PDB Wrote: Very tedious work.

Yep. I'm beginning to accept that I will have to go through the entire movie with a fine tooth comb!
Reply
Thanks given by:
#8
(2019-02-15, 07:56 PM)NeonBible Wrote: Yep. I'm beginning to accept that I will have to go through the entire movie with a fine tooth comb!

[Image: enhanced-buzz-25438-1377800022-18.jpg?do...ality=auto]
Reply
Thanks given by: LucasGodzilla , NeonBible
#9
(2019-02-15, 12:31 PM)NeonBible Wrote: I was reading about sample rates. DVDs use 48KHz while VCDs use 44.1KHz. Would resampling effect speed and pitch?

The difference in sampling rate is not the cause of the drift.
Reply
Thanks given by: NeonBible
#10
I suppose in those cases, working from the video master will help you sync better because you can point out the missing frames in any place whereas with audio you're kinda blind. Also when the sync echoes doesn't mean there's a frame difference it can sometimes just mean the sources weren't running at the exact same speed, but on screen, you wouldn't notice.

So when you align the sync so that they match exactly, you are messing up with the rest of the sync along the line. The further you cut out ms to match, the further it goes out of sync further. You need video to be absolutely exact, and not bother that every line doesn't echo.

This from my experience syncing the Terminator mono tracks.
Reply
Thanks given by:


Possibly Related Threads…
Thread Author Replies Views Last Post
  VHS Audio Question alleycat 5 227 2019-09-07, 10:27 AM
Last Post: Evit
  Audio - HD video with SD inserts? alleycat 9 146 2019-09-06, 05:08 PM
Last Post: TomArrow
  AudioMedian Tool (Median from multiple audio files) TomArrow 5 450 2019-08-23, 03:05 PM
Last Post: TomArrow
  Beginners Guide To Syncing Audio alexpeden2000 19 7,127 2019-08-01, 09:47 PM
Last Post: NeonBible
  Synchronizing Laserdisc audio to Bluray - missing frames Colek 14 4,215 2019-02-28, 08:11 PM
Last Post: Stamper
  Comparing Audio Fidelity alexpeden2000 3 338 2019-02-17, 04:32 PM
Last Post: alexpeden2000
  Audio and frame rates? Serums 2 849 2018-05-08, 02:56 PM
Last Post: Serums
  [Help] 2 VHS Audio Captures to remove faults. CSchmidlapp 9 2,049 2018-04-13, 06:46 PM
Last Post: CSchmidlapp
Information The Importance of the "Original-Speed" Audio jerryshadoe 25 9,342 2017-04-12, 02:16 PM
Last Post: jerryshadoe
  Mastering Laserdisc audio Colek 7 4,137 2016-01-23, 01:11 AM
Last Post: jerryshadoe

Forum Jump:


Users browsing this thread: 1 Guest(s)