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Audio sync operation is painfully slow


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I'm working with a camera video file with its own audio, plus two separate audio tracks, and occasionally a second camera that gives another video and audio track. I tried right-clicking the audio from one camera clip and one mic clip, about 3 minutes long in both cases, and choosing "Sync Audio". Several minutes later I'm still waiting for a result, and the progress bar is showing maybe a little over 10% done. In contrast, in Kdenlive, including the selection time for setting the reference and the other clip, the whole operation took about 20 seconds.

Is it really normal for this to take so long in Videopad? Is there some way to speed this process up? If not, looks like I'll be doing all of my initial edits to line up sources in Kdenlive...and maybe all editing if it turns out faster overall for other types of edits as well.

Videopad seems to have tried to sync ALL the audio in the project, not just one clip, and the whole projected was over an hour long, and doesn't just contain two different mic tracks, but also a guitar track, and one short clip from another angle with a mic recording the same source as the other two. The end result was a mess--everything got shifted way over to the right except the guitar. In the end only the tail-end of the guitar track overlapped with any of the other stuff at all. No idea why--is the program thinking it's supposed to align the mics with the guitar? That's not what I had in mind, since the guitar clips are exactly the same length as one of the other tracks, and they had already been grouped with their respective mic clips, so I would have expected the guitar to move with the ones it was grouped with, but apparently the sync thing overrode the grouping, much like the video ripple thing seemed to do a couple days ago.

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Selected clips will sync to the unselected clips.  In this two-track example, an A/V clip follows a music clip.

The goal is to use the sync feature to align track 1 to track two...


The result...


All track clips are shifted accordingly.  Don't group.

If other clips/tracks are not to be affected, sync each clip independently - perhaps in another sequence - then copy all <ctrl-A> <ctrl-C> and paste <ctrl-V> into the main sequence at the desired location.  Or the synchronized sequence can be exported, creating a clip to be pasted into the main.

In no case did a four-minute track take longer than :30 to sync.  While it's best to keep things simple, multiple auto-sync can do this...

If you make a mistake along the line, <ctrl-Z> will backtrack, step-by-step.  And, of course, Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves.  Using Save Project Files (no AS) will overwrite.  From the HOME tab, that choice is available by clicking the caret to the right of the Save Project button on the toolbar.

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Thanks Borate. So sounds like the sync feature works per sequence, and I'll have to create a new sequence for each group of clips to accomplish the sync before putting them all together in one sequence, and I might have to wait to add the guitar track until all the vocal mics are synched. (The help file is rather light on details: http://help.nchsoftware.com/help/en/videopad/win/content_syncaudio.html ). I'll give that workflow a shot and see how it goes.

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Ok, well, that did not work. I added a new sequence and copied one set of clips into it. I tried clicking the camera audio clip in that and doing the Sync Audio thing. It said "No matching sound track found." I tried clicking the mic audio and got the same result. Didn't matter whether the guitar track was present or not--initially I left it there to see what would happen, but removing it didn't change anything. I tried a different set and got the same results.

Ideas? It's very obvious in the wav form that the clips I'm attempting to sync are from the same take. Yeah, the camera has more background noise, but the peaks are clearly following the same shape.

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Doubtful.  If the files don't have similar waveforms/contents, VP won't be able to match them.

Share the project, with the files that you're trying to sync showing on the timeline (in their non-aligned positions).

  •     Back up --- With your project on the timeline, click on MENU at the top-left.  Click FILE|BACK UP PROJECT FILES TO FOLDER.  Choose a folder and SELECT FOLDER.
  •     Upload ---  Use a free server - Google Drive, MS OneDrive, etc.* - to upload the saved, numbered FOLDER.    Do NOT upload the individual VPJ or export file. 
  •     Get link --- Get a public link.  If using Google Drive click GET SHAREABLE LINK. If necessary change "restricted" to "anyone with the link can view" 
  •     Share ---     Click COPY LINK | DONE.  Paste that link here, or click the folder at the top-right of this forum to message it privately to me.  It won't be shared.

          *    Before uploading, right-click the folder, click PROPERTIES.  Look at the File Size to confirm that it's not too big for the free space on the server.

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I think I figured out what the problem that triggered that error message was. My video camera records audio at 48khz. My DAW (Reaper) and audio interface were set to 44.1khz. In Reaper the sample rates can be mixed and matched, no big deal, it figures it out, so I didn't think to make sure Reaper and my audio interface were set to record at 48khz before doing these test run videos and audio recordings. Apparently Kdenlive and Shotcut can figure it out with different sample rates, too--neither had any trouble doing a sync, regardless of how many clips I was working on. (Audio for this project is three main tracks with 15 clips per track, plus a couple overlay tracks with just one or two.)

But in Videopad, if I imported the audio at 44.1khz and the video at 48khz, I got that error, "No matching sound track found." But after converting the audio files to 48khz with Reaper, then importing the same clip, the sync on a single mic clip compared to a single camera clip worked.

So it seems that Videopad will only sync audio if the sample rate matches. I suspect the reason Videopad was able to do some sort of sync attempt when all the files were in one sequence, but took forever and botched it badly, is because it did find one other 48khz clip, probably from my second camera rather than any of the audio-only tracks.

I also did a test both on this computer and on a second computer with a fresh Videopad installation where I put 3 of the camera clips and the matching, resampled 48khz audio-only mic clips into a sequence. Selecting either just one or all of the mic clips and trying to do Audio Sync took a while but it appeared to work--however, on listening, only the first clip I selected actually ended up in sync. The second was audibly out of sync like a very short delay effect where it overlaps but sounds weird, and the third was way out of sync like a long delay effect with totally distinct repeat. If I selected the second clip and tried again, that clip got synched, but then the first that was previously synched got out of sync.

And my final test was using one clip from the main camera, one clip from the mic, and one clip from a second camera (phone). In that case the mic synched with the main camera, but the phone track remained way out of sync.

So as suggested by earlier results and our prior discussion, it does indeed appear true that only one clip can be synched to one matching clip at a time--any attempt to go beyond that, either in terms of other sources or other takes, fails to give usable results. Which means to work with 15 clips I'd have to make one or more sequences just for synching, then move clips over to the main sequence one at a time, and when working with a third track, manually place that track's clip in the main sequence over the other two related clips according to the sync results.

The apparent "sample rate has to match" limitation of the audio sync feature doesn't appear to be mentioned anywhere that I can find--but it's pretty important, so if it's an intended limitation, better add it to the help files. If it's unintended, I'd call that a bug.

Same goes for the problems with synching multiple files at once--that's a pretty big limitation vs. the open-source editors I tried, and it needs to be clearly stated up front to avoid wasting time on this sort of troubleshooting, or to be fixed if it wasn't the intended behavior.

Either way, it's an area that needs improvement in Videopad, as it looks like it will be much faster to work in Kdenlive or Shotcut for the initial stage of simply synching up sources. Not sure yet about other types of edits like overlays or pan/zoom/crop effects--I actually think the most user-friendly version of the latter group is in Photostage, unless you need to enlarge.

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File a suggestion, and reference this thread.

Multiple files can by synchronized, as demonstrated in an earlier post.

In single sequence, sync a segment, then export.  Clear the sequence, and sync the next. 

The resulting clips can be added to the main sequence.  Processing should be efficient.

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