Audio sync drift problem with HVX200 P2 capture

[Arthur Vincie]

The H.264 file suffers from the same problem (audio slate is one/two frames off from visual clapper) – when playing back in FCP. You can’t really scrub in QT frame-by-frame AND check audio, so again I’m not sure if this is an FCP issue or a footage issue. I’ve asked my DP to check his camera settings.

The audio doesn’t seem to drift from the front to the end of the clip, though if it was a really slight drift I probably wouldn’t notice it since the clips are relatively short (5 minutes is long).

[Arthur Vincie]

“As far as I know” – means just that. FCP says “23.98” as the timecode base for the clip video and audio, but that doesn’t mean anything, since it’s shorthand for 23.976.

I’ve played the clips in QT and the problem remains the same. However, it’s a little harder to check since there’s no way to scrub video AND audio one frame at a time in QT (you can advance/retreat by one frame but the audio doesn’t play, unless there’s a control I’m not aware of).

My clips are fairly short, but they do seem to stay exactly 2 frames off (I’ve encountered a few clips that are exactly 1 frame off, though I’m not sure what that means). If there is a drift it’s so subtle that it’s not cropping up in the 2-3 mins. average length of the clips.

The Canon E1 plugin for FCP didn’t give me any choice as to framerate, but since it was made by Canon specifically for Canon 5D footage I’m assuming (maybe a bad assumption) that they’ve thought of the framerate discrepancy.

Have checked with some other editors and my DP and they’re looking into both my footage and the problem in general. Could be a camera issue.

When sliding the audio a frame forward it syncs up fine, so I’ve proceeded with my logging in the meanwhile. Just hoping I’m not overlooking something that will bite me in the butt later on.

[Jeff Sandmann]

Ron,

I’m having pretty much the exact same problem you were having in October. I’m bringing in 1080i 24p clips from a Panasonic HPX-300. When I look at the clip in QT on my machine the audio syncs fine. It’s only when I get them in FCP that I get the audio drift.

It sounds like Jeremy helped you with your problem which basically had to do with somehow converting your footage from 23.98 to 23.976. I’m thinking that would work for me to, but my question to you is;
How do you go about doing that? You talk about transcoding your footage but I’m not sure I follow what that’s all about. What program are you using?

Thanks,
Jeff

[Ron Dawson]

Hey Jeff

I use MPEG Streamclip to transcode my DSLR h.264 footage to a format the I can edit in FCP. I use ProRes format. As long as I don’t enter any specific frame rate in MPEG streamclip, it’ll default to the clip’s natural frame rate of 23.976. My problem before was that I was specifically entering the frame rate 23.98. That was causing the problem in FCP.

Not sure how you use your footage, but you were calling it 1080i 24p. That’s kind of an oxymoron. Either it’s 1080p at 24 fps, or it’s 1080i. I don’t think that’s your problem per se, just pointing that out.

Are you able to use footage out of the HPX in its native format, or do you need to transcode it first? If the latter, whichever program you use, either leave the frame rate field blank, or specifically enter the exact frame rate of your footage, which in this case sounds like 23.976.

Hope that helps.

~ Ron

Ron Dawson
Executive Producer/President
Dare Dreamer Media

Creating films that inspire and encourage the human spirit.

*** Dream Out Loud ***

[Cuauhtzin Gutierrez]

Hello,

I know this post is about a year old but the original issue was never solved and I’m having the same problem. Footage was shot on an HVX at 30p and after everything was captured off the P2 card the audio is out of sync. If I play the clips back on the camera, the audio is in sync and perfectly normal. Trying to play the captured clips in QT and FC shows the audio is off.

I have a few interviews and all of them are out of sync. It seems like the audio drifts further out of sync as the clip progresses. I try to line up the audio (about 20 frames) and it appears to be in sync for short while, but as the clip keeps playing it goes out of sync again.

Does anybody know what the problem could be? Thank you in advance.

[Ron Dawson]

Hi,

This problem was solved for me on Creative Cow. I don’t know if this is your same solution, but this was what happened with me:

I was having the same problem you described. Exactly! (drifting getting worse as the clip progressed, etc.) It turns out the problem was that when I transcoded the 24p footage (shot on a DSLR) in mpeg stream clip, I manually set as the frames per second to exactly 23.98. I did this b/c in FCP, that is the short-hand used for 24p footage. However, the footage is really 23.976. Even in FCP, it really is 23.976, despite the fact that is says 23.98 all throughout.

The problem is this: if you drop footage into FCP that is at a frame rate that is not recognized by FCP (e.g. 23.98 vs. 23.976), you get the drift.

I solved the problem by leaving the fps field in mpeg streamclip blank. By doing that, mpeg streamclip will transcode the footage at the source material frame rate, which is actually 23.976.

You didn’t mention that you were transcoding, so my guess is that the 30 fps footage is exactly 30 fps. I think (but I’m not 100% sure) that exactly 30 fps (vs. 29.97) is not recognized by FCP. I wonder if you transcoded the footage to 29.97 if that would solve your problem?

Ron Dawson
Executive Producer/President
Dare Dreamer Media

Creating films that inspire and encourage the human spirit.

*** Dream Out Loud ***

[Cuauhtzin Gutierrez]

Just tried exporting the video as 29.97 in mpeg streamclip… no luck.

I found another thread on here that described my problem perfectly just like the OP. https://forums.creativecow.net/readpost/193/883011

I’m guessing the settings on my camera were a bit screwy. Seems like the video plays at 24fps while the audio is at 30fps. The audio can’t catch up with the video which is why it keeps going out of sync even when I line it up manually. Not sure why it plays back fine on the camera but once imported it’s off sync.

It’s not perfect, but the work around I’m using now is leaving the audio alone (in a 29.97 timeline) and slowing the video down to 90%. It doesn’t always look perfect but it’s the only option I have (I think). Covering up a lot of the interview with b-roll is helping too.

Never shooting at 30P again. I’ve shot in 30PN before and it worked fine so that’s what I’m sticking with from now on.

Thanks for the response!