Supplied audio track is not in sync with video

Julius_ wrote on 7/26/2024, 10:25 AM

Hi All,

I am no expert in audio and this might be a user issue.

I recorded a concert last night in 45 minute segments. I recorded in 4K at 29.97 FPS. The sound was also recorded thru the camera's internal microphone. Everything is in sync and no problems. Except that it's not the best sound captured via the internal camera mics.

The sound guy gave me a USB key that had recorded the event with much better, crispier sound (than my internal mic obviously) and I would use his captured sound.

In Vegas 21 (latest build). I line everything up in the timeline, but at some point, it's out of sync in my timeline (not rendered). You can see via the waveform that it's out of sync too. I did try to render, but as expected, it was out of sync.

My timeline is set to 1080p at 23 (I also tried 30).

Is there something that I can do to correct this?

Thanks

 

The audio file:

General
  Name: R_20240725-193247.wav
  Folder: K:\Capture2024\RobertAdams_Band\Audio
  Type: Wave (Microsoft)
  Size: 503.09 MB (515,167,084 bytes)
  Created: Friday, July 26, 2024, 10:15:28 AM
  Modified: Thursday, July 25, 2024, 8:21:52 PM
  Accessed: Friday, July 26, 2024, 11:18:24 AM
  Attributes: Archive

Streams
  Audio: 00:48:40.448, 44,100 Hz, 16 Bit, Stereo, Uncompressed
 

 

 

Comments

john_dennis wrote on 7/26/2024, 11:53 AM

I'd start by converting the USB key audio file to 48kHz to match the most likely format of your video recording before placing it on the timeline.

DMT3 wrote on 7/26/2024, 11:56 AM

Unless the camera and the audio recording device are locked together thru existing technologies (gen lock, time code generator,etc) there is no expectation that they will stay in sync. You can either find points where you can edit the audio to bring it back into sync for a period of time or use varispeed and force the audio into sync.

Julius_ wrote on 7/26/2024, 12:19 PM

I put the audio in vegas and rendered to 48Khz...still off by a few seconds...

Original audio from camera is

 Audio: 00:27:10.629, 48,000 Hz, Stereo, PCM

 

The converted to 48Hz is: (audio clip is longer because the guy kept recording)

 Audio: 00:48:40.463, VBR, 48,000 Hz, Stereo, MPEG Layer-3

 

I really hate audio.

john_dennis wrote on 7/26/2024, 12:34 PM

Convert to WAV and avoid the lossy conversion to .mp3 while changing the sample rate to 48kHz. Then follow @DMT3's advice to split and stretch as required.

I hate mp3 and have since I read about the emerging technology in the Wall Street Journal decades ago.

mark-y wrote on 7/26/2024, 12:51 PM

You are experiencing clock drift. What I do is to chop the audio into ten minute chunks or so, cutting them precisely at zero waveform crossings to prevent clicks, and moving each segment around to sync. You will have slight gaps or overlaps that usually go unnoticed.

There is also AudioSyncR at tools4vegas.com It is not free and there is a bit of a learning curve.

Julius_ wrote on 7/26/2024, 12:52 PM

yeah, converting to wav did little....how do you stretch audio?

Julius_ wrote on 7/26/2024, 2:10 PM

I think I see the problem....during the recording to the USB key, I think it hiccups from time to time..maybe not fast enough of a USB key.....what a pain!


Note to self...next time plug directly in camera!

Julius_ wrote on 7/26/2024, 2:57 PM

Yup, I can confirm that the audio recording to the USB key hiccups at times (for about 3-4 seconds).

I still hate audio.

 

jetdv wrote on 7/27/2024, 9:45 AM

how do you stretch audio?

Hold down the CTRL key and resize the audio. Sounds like you don't need to do that now, though.

Doing sound for a wedding today - I'll give them a CD, not had people have issues with a CD...