Is the HVX dropping frames or is this a NLE problem?

C

conrad787

Member
I use the HVX to record myself playing drums. I play along to music with headphones, then in Final Cut, sync up the HVX footage and the imported song file by hand. My sequence preset in Final cut is DVCPRO HD 720p24. Final cut tells me:

"Use this preset when editing with 720p DVCPRO HD 23.98 fps material."

The problem is that every 30 or 45 seconds into the song, it slowly starts to get out of sync. Near the end of a three minute song, the video + audio that was captured with the HVX and the song imported into FCP are about a 1/4 second off.

My temporary solution is to remove a few milliseconds of the MP3 I imported every 30 seconds in the sequence. This keeps everything in sync.

Why does the footage slip out of sync with the imported audio? It's as if the HVX is losing a frame every so often, so my recorded footage gets EARLY, before the actual song. Or, is this a problem with the sequence preset that I'm using in Final Cut? Despite the fact that I've chosen 720p24, as I wrote above, Final Cut tells me this is the appropriate preset to use for 23.98 material.

Thanks,
Conrad
 
not dropping frames. its exceedingly likely a difference in the rate of playback between the mp3 and your recording framerate.
 
I don't think the mp3 is the problem... I played along to the same mp3 as the one I imported into Final Cut. I don't think Final Cut should have a problem consistently playing back a 3 megabyte mp3 file...

I also doubt that the HVX is dropping frames. Does that mean that my Final Cut can't keep up with the playback of my p2 footage? That's why every so often, it loses a frame of the video and it starts to get out of sync? Is this definitely not a problem with my sequence preset?

My computer is a 17" Macbook pro, 2.6 Ghz x 2, 4 gigs of ram. That should definitely be able to play my P2 footage.

Conrad
 
YOu misunderstand. Your MP3 file does not run at the same rate as your recorded video. They are running at different rates...therefore they drift out of sync. And yes, FCP doesn't like working with MP3s...it wants AIFF files. 16bit stereo 48kHz.

Even then it might not work. There are tricks to make sure that the playback audio on set matches the record rate of the camera. I don't know the tricks, I just know they exist.
 
thanks shane! yeah conrad, what i mean when i say "rate of playback" is that your mp3 is most likely based on a different time base than that of your video. id imagine in this case straight SMTPE timecode (or maybe 30fps) vs 23.98fps framerate.
if thats the case they will drift out of sync over time - about as much as youve described.

i had a similar situation (which led to a lawsuit) several years ago based on the fact that my media100qx system had a frame rate disagreement with the bundled adobe premiere software and would NEVER produce synced end product longer than 30 seconds in length.
 
Try this. Import the MP3 into FCP then export that to a proper AIFF 48k file. Reimport that into FCP and perform your musical take by playing it from the FCP timeline. (You did not mention what you were using as playback...Playback off an ipod, for example, is sure to drift badly) You are only as in sync as the match between the clock from your playback source and the clock from the HVX.
Good luck
 
Here is what you could do.

Play the mp3 out to your playback monitor but simultaneously record it in to one track on the HVX via Line input. Use the other track to record your drum track.

Has to be in synch.
 
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