How to make DV Start/Stop Detect subclips, when using imported audio?

Question

How to make DV Start/Stop Detect subclips, when using imported audio?

I've captured a 1-hour clip from my DV camcorder, that was originally recorded at 32 kHz. I originally planned on converting that audio to 48 kHz within FCE (see http://discussions.apple.com/thread.jspa?threadID=339703&tstart=0 ). However, FCP has a batch export feature that would save me many many hours of time, so I was thinking about buying FCP. I posted a question related to this audio conversion in the FCP forum (see http://discussions.apple.com/thread.jspa?threadID=386154&tstart=0 ). There, a respondent recommended doing the audio conversion external to FCP, using Quicktime Pro, for example. I'm not exactly sure why this would be any better, but I thought to give it a shot anyway.

So I've tried using Quicktime Pro to convert audio from my 1-hour clip. I imported the converted audio file back into FCE. But at this point, I'm stuck.

Originally, using Mark>DV Start/Stop Detect, I marked up the original 1-hour long clip (still with the 32 kHz audio). Then I selected all the marked segments (appearing under the clip in the Browser), and chose Modify>Make Subclip. That made all the segments into subclips. I could then use Batch Export (in FCP) to export all those subclips as individual clips. But those clips would have 32 kHz audio, and I want 48 kHz audio.

I'm not sure how to accomplish the same thing, with the 48 kHz audio that I've just created in Quicktime Pro, after importing it into FCE.

If I put the original 1-hour long clip into a sequence, delete the 32 kHz audio tracks, and lay down the 48 kHz audio in its place, I get the whole 1-hour long sequence. But I can't figure out how to split this sequence up into subclips like I did with the original clip. The markers are still there (on the video clip). But what do I make into subclips? There are no segments in the browser that correspond to the sequence, only the segments under the original clip with the 32 kHz audio.

It seems like I need to replace the audio of the original clip with the new audio, but I'm not sure how to do that in FCE (or FCP).

I have an additional, perhaps less important, question.

When using Quicktime Pro to resample the audio from 32 kHz to 48 kHz, are these export settings most appropriate?

Format: Linear PCM
Channels: Stereo (L R)
Rate: 48 kHz
Sample Rate Converter Settings: Quality: Best
Linear PCM Settings: Sample size: 16 bits

I hope someone can help!

PowerMac G5 Quad 2.5 GHz 3GB RAM Mac OS X (10.4.5) NVIDIA GeForce 7800GT

Posted on Mar 6, 2006 2:57 AM

Reply

Answer 1

Tom Wolsky

Level 10

152,819 points

Mar 6, 2006 5:01 AM in response to Anthony M Kassir MD

There's nothing you can do. The date/time metadata has been lost in the re-encoding of the video.

The best you can do is cut the material manually with In and Out points converting them to subclips, or use extended markers to segment the sections you want to subclip.

All the best,

Tom

Reply

Answer 2

Mar 6, 2006 9:35 PM in response to Tom Wolsky

Hi Tom:

I didn't re-encode the video. I just exported the audio only, converted that to 48 kHz in Quicktime, and imported the audio back into FCE (as an aif audio file).

Does your statement, "There's nothing you can do," still apply? If that's the case, I'll have to do the conversion in FCE or FCP.

Is there any reason NOT to do the conversion in FCE/FCP?

One discussant has recommended doing the original capture with Easy Setup preset to 48 kHz, even though my tape is 32 kHz. Would this suggestion work, or could it cause problems? I thought the Easy Setup had to match the configuration of the tape. This suggestion was given in the FCP thread, http://discussions.apple.com/thread.jspa?threadID=386154&tstart=0

Message was edited by: Anthony M Kassir MD

Reply

Answer 3

Tom Wolsky

Level 10

152,819 points

Mar 7, 2006 3:11 AM in response to Anthony M Kassir MD

If you exported the audio only then no. But are you going to sync up the audio by hand in Final Cut?

Don't do it through Final Cut, the audio is not clean.

This will work in some instances with some decks and FireWire protocols. The application does not actually convert the sample rate I don't believe, simply reassigns it and changes the timing so it matches the video length. It appears to be 48k in Final Cut, but I don't think any real-time, on-the-fly conversion occurs. It is also not supported by Apple, can cause loss of sync, and will not work on many systems.

All the best,

Tom

Reply

Answer 4

Mar 7, 2006 10:56 PM in response to Tom Wolsky

> If you exported the audio only then no. But are you

going to sync up the audio by hand in Final Cut?

Well, I only have a single 1-hour long clip. So syncing the audio is really easy, at least in the timeline. I just drop the audio so the beginning of the audio matches the beginning of the video.

> Don't do it through Final Cut, the audio is not clean.

OK, so doing it through Quicktime is a better process, I guess.

So, I'm still in need of a little guidance. After doing the conversion in Quicktime and re-importing the audio into FCE, I'm stuck.

My goal is to mark up the hour-long clip using DV Start/Stop detect, then make each section into a subclip for later exporting of chosen individual clips as self-contained files. But I need to make the audio 48 kHz, at some point in the process, preferably before I export all the subclips as self-contained files.

In other words, I want to convert all the audio at once while it is still a single clip, then divide up the clip using DV Start/Stop Detect.

Should I get rid of the audio that is part of the original captured clip, and replace it with the newly converted audio that I made with Quicktime? Do I create a new clip somehow? Can I still use DV Start/Stop detect on that new clip?

Please help! 🙂

Reply

Answer 5

Tom Wolsky

Level 10

152,819 points

Mar 8, 2006 7:05 AM in response to Anthony M Kassir MD

After you've converted the audio, put the original video and audio file into a sequence.

Delete the old audio.

Put the new audio in its place. I'll probably line up pretty well as it should just be a file conversion.

Link the new audio with the old picture.

Drag that linked file into a bin and run DV start/stop detect on it.

Reply

Answer 6

Mar 8, 2006 11:09 PM in response to Tom Wolsky

Hey Tom:

Thanks. That helped a lot. When I put the new audio under the video in the sequence, I noticed the new audio was a few frames (30 or 31) longer than the original clip. When I viewed the audio waveform in the viewer, I saw that there was empty audio at the beginning (14 frames) and end (about 16-17 frames). Setting the In and Out points for the audio appropriately let me match up the audio and video perfectly.

I wonder why an additional half-second is added to the audio on each end. I think it happens when FCE exports the audio, before it is touched by Quicktime. In any case, setting edit points corrects this problem.

Linking the audio and video and dragging the linked file into the browser created a new clip and then DV Start/Stop detect worked fine.

Next step: Buy FCP and use Batch Export, and voila! My work (for now) is done.

Thank you thank you thank you!

Reply

Answer 7

Mar 9, 2006 12:01 AM in response to Tom Wolsky

BTW, do you have any tips on how to make sure the audio is entirely in sync with the video, after you upsample in Quicktime, re-import, and trim the ends to match the duration of the video?

If I'm setting the audio In and Out points for the audio clip a frame or two too late, the video and audio will be out of sync ever so slightly, perhaps beyond my ability to perceive it.

Reply

Answer 8

Tom Wolsky

Level 10

152,819 points

Mar 9, 2006 5:09 AM in response to Anthony M Kassir MD

Open the audio into the Viewer and holding the Shift key drag the playhead. You can mark an In point up to 1/100th of a second. You should be able to get it pretty precisely in sync.

Reply

Answer 9

Mar 9, 2006 8:27 PM in response to Tom Wolsky

Hi Tom:

Thanks for the help. Do you mean to mark an in point in the new audio after it has been imported, or the old audio before it is exported?

Also, is there a way to place a mark in both the video and audio before exporting the audio, convert the audio in Quicktime to 48 kHz (while preserving the marker), and then reimport the audio with the marker intact? That would allow me to match up the video and audio precisely.

Otherwise, I'm just guessing because I can't tell by watching the video if the audio is off by a few frames, not to speak of hundredths of a second.

Reply

Answer 10

Tom Wolsky

Level 10

152,819 points

Mar 10, 2006 9:22 AM in response to Anthony M Kassir MD

After you import.

No there's no way to export a marker using QuickTime Conversion.

Reply