Audio Synchronisation gradually degrades

[michael9Member]

I’m using vg20 and a VG10 for interviews. I bought a Tascam DR-40 to get a better quality (less affected by ambient noise) audio track. I’m using Premiere Pro CS5.5. I can synchronize the files accurately from a sighted clap but by the end of the interview (say 40 minutes) there’s a lag between the video and the DR-40 even though all was well to begin with. I’m importing four .mts files directly to the timeline. Is it possible they are not entirely seamlessly joined and that the lag is due to small discontinuities in assembling the clips? Is there a way to turn the four clips into a continuous clip prior to bringing them in to Premiere. I know PMB won’t look at the files once they’re on the hard drive (mildly annoying). Hope someone can help because what I’m getting is otherwise starting to look pretty good (IMHO).

[HarlinParticipant]

If you import the whole folder from your sd card to your project file cs5.5 should auto join everything fine. Also make sure your tascam is set to 48k which is the video audio standard.

Harry

[DanielMember]

I’ve seen this problem before and I know it has to do with frame rates that don’t match up. Like, the video is actually23.976 fps as opposed to 24. I don’t know EXACTLY how it works or the technical terms. (If someone could step in and help me out that would be great.) Sometimes, you can just slow down the audio, (like to 97%) so that it stays in sync.

[CvilleParticipant]

I have the Sony VG 20 and it comes with software that I understand will put the clips into one continues file.

If you look at the sd card directly thru windows a continues 40 minute clip will appear to be several individual clips. If you utilize the software it becomes one clip.

I use Sony Vegas Pro so I have never used the included software. Vegs has a device explorer that allows you to import the video directly from the camera and it does the same thing. It sees it and imports the video as one continues clip.

[michael9Member]

 Thanks for the help. I’ll try a few of the suggestions and see what happens. Maybe Pluraleyes could be a good option here.

[CharlesParticipant]

If the codec is AVCHD then import the whole AVCHD file to your computer. PP will then recognize it as one continuous clip. Found it out the hard way.

[michael9Member]

Thanks Charles. You know, that’s what I expected. The camera breaks the session into 2.1 gb files as it goes and I thought just bringing the folder in with all the files present would result in a continuous file (so much easier for video and audio adjustments). I drag the folder to the timeline and yep, there they are again, four clips stuck together, each requiring the same adjustments to be repeated for each clip.

[CharlesParticipant]

Did you download Sony’s video editor and try just rendering the footage to see what happens?

[CvilleParticipant]

As I mentioned in my previous post im pretty certain the software that comes with he camera will put all of the pieces together so you don’t have any missing frames.

[michael9Member]

 Haven’t run any long sessions yet to test that out. One of the reasons I hadn’t used PMB was that it won’t recognise the sdhc card in the computer. You have to download directly from the camera which means finding the right hdmi cord … a minor issue but you can see that just popping the card was the easiest option.

Good news though, I can report that PluralEyes handled my audio issue well.

[michael9Member]

As Charles suggested, PMB is the way to go here. gets all your ducks in a row without fuss.

[paulearsParticipant]

I don’t think a few frames adrift after 40 minutes is unusual. I’ve never tracked it down to anything other than slight inconsistencies in the bit rate between equipment 48,000 samples a second, or 47,993? I just select a few re-sync moments in the files and then do a very short crossfade on the tracks to put them right. Very often as the slip is maybe 1 or two frames, you can re-sync the audio tracks visually by matching the peaks and troughs in the waveform. razor split the track, drag right to create a bit of space. find an identifiable peak, drag a frame or two to match the others. Rarely any more than this. The go back to the gap, extend the track to fill and then add the crossfade. Takes very little time. My projects tend to be 3 or 4 cameras and continuous recording of 45-60 mins. I expect at least one re-sync in each section. Occasionally there’s no need, but it’s pretty common I’ve found.

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