Audacity Forum

I'm brand new to audio editing. I'm a hobbyist with video editing. I have a movie file in which the audio and video are out of sync.

I have a few basic tools, among them Ffmpeg which I have used to convert an avi file to VIDEO_TS. The sync issue is not present in the original avi file. It shows up in the resulting DVD (VIDEO_TS) file. The audio is about 1.25 seconds ahead of the video and appears to be consistent through the movie. In addition to the finished DVD file, the conversion process also puts out separate ac3 and m2v files.

My work flow was to edit the ac3 file in Audacity and mux with the m2v file back into a DVD file.

I made an attempt last night at an edited version and it did not work. I'm certain my Audacity workflow leaves something to be desired. Essentially what I did was:

1. Open the ac3 file
2. mix and render the 6 channels
3. Used the time shift tool to "shift the audio" to the right (need about 1.25 second shift)
4. Saved and exported
I could not find a way to 'fine' tune my shift/adjustment by ms (tenths/thousandths).

Any pointers/kick start/help greatly appreciated.

The first thing is to check that the fault really is with the file and not with your player - try playing it in (the free) VLC player. http://www.videolan.org/vlc/download-macosx.html

If you still have the problem -
In Audacity, zoom in very close (using either the "zoom" buttons or Ctrl+mouse wheel) and you will be able to drag to an accuracy of 1 sample.

Did your original video come from a Sony DVD?

stevethefiddle wrote:The first thing is to check that the fault really is with the file and not with your player - try playing it in (the free) VLC player. http://www.videolan.org/vlc/download-macosx.html

My edited dvd plays the same in the Mac DVD Player, VLC and the home dvd player (an inexpensive sony player)

stevethefiddle wrote:
If you still have the problem -
In Audacity, zoom in very close (using either the "zoom" buttons or Ctrl+mouse wheel) and you will be able to drag to an accuracy of 1 sample.

Ok, question here is what do I do from there to add to the front end, to 'shift' the audio, can I just add 1.25 second blank recording?

stevethefiddle wrote:
Did your original video come from a Sony DVD?

No the original is an avi file I am converting to DVD. The file was downloaded.

Thank you for the reply.

macbuz wrote: <<< In Audacity, zoom in very close (using either the "zoom" buttons or Ctrl+mouse wheel) and you will be able to drag to an accuracy of 1 sample.>>>

Ok, question here is what do I do from there to add to the front end, to 'shift' the audio, can I just add 1.25 second blank recording?

You can drag the audio to wherever you like - you can chop it up into little pieces and move them around on multiple tracks - you can spread the bits out, change the order, push them up close and even overlap different tracks... pretty well whatever you like.

When you "Export" the edited audio, Audacity will mix and render the project into a single continuous audio file. Any gaps in the audio (including any gap at the beginning) will be rendered as silence.

To see exactly how the Exported audio will turn out, select everything in the project (Ctrl+A for Linux and Windows) then select "Mix and Render" from the "Tracks" menu.

Note on Exporting - the exported audio file will be at the same sample rate as the "Project Rate". You can change the project rate at any time by selecting the required rate in the Project Rate box in the lower left of the main Audacity window.

stevethefiddle wrote:When you "Export" the edited audio, Audacity will mix and render the project into a single continuous audio file. Any gaps in the audio (including any gap at the beginning) will be rendered as silence.

Ok - I'll dig in and see what I can do, granted all I want is probably as basic an 'edit' as can be, but to a novice it's still greek -

The first time I tried exporting the file from Audacity, all 6 tracks were showing, and as it exported it was producing individual files for each track to my desktop. This is why I figured a mix and render prior to exporting was necessary. Perhaps there's a selection option I missed that produced the separate files.

Off to figure out how to create my 1.25 second addition. I hate learning curves

Is there an info window that tells me the time length of my file? Or is it one of the text boxes at the bottom of the main window next to the Project Rate?

macbuz wrote:Is there an info window that tells me the time length of my file? Or is it one of the text boxes at the bottom of the main window next to the Project Rate?

It's the boxes at the bottom. You can select various formats for them to display - click on the little arrow on the edge of the box.
The middle box can be set to show either the length of the selected region, or the end time of the selected region.
To select everything, it's Ctrl+A for Windows/Linux, and will be something similar on Macs.

Thank you .... seems I may be getting somewhere. I zoomed way in and found the 1 second ticks in the time line at the top and selected 1+ seconds > copied the selection > then pasted it at the front end of each track. It appears to have 'shifted the rest of the audio like i think I need it. Exporting this time did mix and produce just one file.

At this stage of the game, just figuring out the interface and commands is alot. It's similar on Macs for select all - command + A. Off to mux the new audio file and the old video file and see if I got the sync better.

Thanks for your help / guidance / time.

macbuz wrote:Thank you .... Off to mux the new audio file and the old video file and see if I got the sync better.

Thanks for your help / guidance / time.

Yaaaay me ...... perfect??? ..... eh .... maybe not, but ... better??? .... CERTAINLY!!! .... good enough = Yep!!

Thank you very much.