Dual System Sound Sync in FCP
July 3, 2008One of the core processes of any post-production workflow is the synchronization of audio and video from productions using dual-system sound recording (ie when sound is recorded separate to the picture; DAT, Solid-State or hard disc recorder
This can be a bit of a tedious process but obviously a crucial one. There are a number of ways to do it. Electronic slate clappers can read off audio timecode which can be matched numerically to picture timecode. The more common method is to sync the visual clap with the audio clap sound manually and link the audio and video files on the time line.
Final Cut Pro offers a good system that allows for audio an video to be synced and linked in the project window rather than having to pull them to the timeline. Its called MERGE CLIPS and the section below, taken from an FCP guide, explains how to do it.
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Assuming you have a slate clap to sync on, simply find the frame in both the audio and video clips
where the clap can be seen/heard and set the in point of each clip to that frame. (ie Load the clip into the source window and set the IN point market on the price frame where the Clapper comes together on the video and where the Clap sound spike is on the audio)
Once you have set the in point in both clips to the frame where they should be synched, select both items in the Browser and choose Modify > Merge Clips. Choose “Synchronize using in points” and click OK.
The video and audio clips will be merged, and a new clip appears in the Browser, named after the video clip but with the appendage “Merged.”
From this point forward, you can treat the merged clip as a single item, with the same linking rules as if the clip pointed to a single media file. However, it will still maintain its relationship to the multiple QuickTime files, source tape, and timecode.
[...] One the features buried in Final Cut Pro’s Modify menu is called “Merge Clips.” What this tool does is enable you to link two disparate audio/video sources so that FCP treats them as a single clip, keeping them synced as you work with the clip while also maintaining their seperate relationships to the source media. This is also referred to as Dual System Sound Sync. Here’s how you do it. [...]
hmmm, what’s the benefit from this over simply adding A + V to a time line (new or the current one) finding sync via the “clap point” (haha) and to THEN link these 2 clips. I’m not sure I would trust the merge clip operation as much as it seems to be at least as many steps with the same, but a less flexible result.
This works but be warned that if you move your media (or lose a drive) and have to reconnect in the future then the merged clips might not reconnect all the media properly.
Thanks for your comments Mishavideo but there very good and obvious reasons to use merge clips rather than do it on the timeline, and its actually more flexible.
If you’ve assembled a sequence it can be a total pain in the arse to then unpack the shots to find the Clap mark on each and synch audio and then reassemble – very much inefficient double handling.
At which point you might be better off doing all the syncing on the timeline Before you edit the sequence. This is Fine and dandy until you have a long form project where the idea of putting all your clips on the timeline bfore you edit is totally dysfunctional and a project managemnt nightmare.
So merge clips becomes a good solution. Do all your synching BEFORE you edit. Put all the merged clips into a BIN of their own and then just work form the mereged cips to assmeble the sequences. Its much more efficient and extremely flexible because you always have the source clips as well that can be used independantly.
Im not sure what you mean by ‘not sure I would trust the merge clip operation’. Its as stable and functional and safe as any other function of FCP.
If you just want to link two clips then its no faster than linking on the timeline but thats not the point. The idea is to use merge to avoid having to unpack and reassemble sequences edted together form the guide track. And also to avoid working on the timeline which is totally dysfunctional for long for projects.
If you’re just cutting short films and trailers there’s no great benefit but try cutting a feature or doco series without using it and you’ll be in for some pain.
As for Scott’s comments; he’s right – moving the project or losing/corrupting the project file can break your merged clips which are virtual rather than real media. But if you use good, professional backup procedures this will never be an issue. Have a read of the Editor’s Guide in the Production Bible section of this site for a ood process of backing up to follow that would avoid any issues of losing merged clips that cant be recovered.
http://ifsstech.wordpress.com/production-bible/
Cheers
Mike Jones
Head of Tech Arts – IFSS
This is helpful, thanks. But, I could use some advice for a problem I’m dealing with at the moment.
I’m working on a project in which the primary audio was recorded dual system, but they recorded backup to camera. I want to replace the back up audio (lots of hiss), but if I merge clips, the wav file seems to merge rather than replace the camera audio.
I tried putting the clip on a sequence, deleting the audio and creating a subsequence, but then merging clips wasn’t an option because it’s a sequence not a clip. so . . .
I can use the audio from the camera as a guide track for cutting and sync back later — but I would really rather work with the primary audio if at all possible for aesthetic and practical reasons.
Any suggestions?
Hi Nikki
Im a bit confused by what you describe. But let me break down the process (one several of my students are wrestling with right now) There are effectively 2 options to start.
A) Sync all clips with the audio tracks BEFORE you start to edit
or
B) Edit using the in-camera guide audio embedded to the clips and then Sync the clips you need to on the timeline by replacing them with the real audio from the dual system.
Obviously you’re working with the later. But perhaps the former would have been better.
Synch up all the clips and creat Mereged Clip copies of all Shots. Then Edit only with the merged clips. The merged clip will add the audio to the existing audio so the original clip may have 2 channels of audio but the merged clip may have 4 – the 2 from on camera plus 2 (stereo or dual mono) from the dual system.
Then you can simply unlink and get rid of the original sound and leave the dual system sound behind which is linked and in-sync with the clip. (I tend to leave the on-camera sound there as a guide and simply mute those tracks out until i dont need them anymore.
If you’ve already done an edit using the on-camera sound then you need to create merged clips and substitute the ones on the timeline with the merged copies.
You could do this the simple way where you drop the merged clips into the timeline on a layer above the originals, line them up and then delete the originals leaving behind only the merged.
Or, slightly more complex, use a REPLACE edit to substitute the original with the Mereged clip.
HTH
Mike
Thanks for this tip. I’ve always synced the sound with the video in a sequence, then used nested sequences, which was a pain. I’ll have to try this out.
The custom has always been to read the slate before the clap. I’ve started reading the slate after the clap. That way I can trim both the audio and video files to the clap. That way I can still hear the slate data in the audio even after the initial trim.
Oh, I also sync the sound at the sub-frame level. Like ifsstech above, I always have a scratch track recorded by the on-camera mic. This gives me a more accurate indication of exactly where the clack occurred. What I mean is that I turn the waveform display on for both the scratch track and the separate sound track and line the clack from the separate sound track with the clack peak in the scratch track. I’m usually not too fussy about it. Just get it within a quarter of a frame seems good enough.
Peace,
Rob:-]
Hi,
When doing an event I run separate audio (stereo but saved as two mono files) together with video and onboard stereo audio.
The video and audio starts independently of each other and are synced by time code transmitter-receivers to jam once. Time code is free running (actual time).
What is a good way of synchronizing this when editing? I don’t think Merge can work because there can be continuos audio with gaps in the video if the camera was stopped for movement etc?
I believe my goal is to get all video/video scattered along track V1/A1/A2 and the separate audio scattered along track A3/A4 according to their individual time code values.
Could this be more or less automatically by using MultiClip etc?
Thankful for any time saving ideas.
Johan
I’m having an issue with this method. I do everything you say, and for the most part, it works, however the problem is that for some reason my audio track will stop before the video track does. In other words, the audio syncs fine for the majority of the track, but for the last 1/3 or so the audio cuts out as the video finishes. Also, the merged clip comes up in the sequence window with what I believe are broken in/out points.
Any advice?
Thanks
Hi All, I have a problem I cannot seem to resolve: I have recorded a one hour lecture using a separate sound source recorded from the sound board. I have no problem synchronizing the sound in the beginning; however, by the end of the one hour, there is a full .5 to 1.0 seconds where the sound has come out of sync. I do not think the sound has a recognizable time code even though it is a high end portable recorder. is there any way that I can compress one hour of audio to shorten it by one second, or correct it otherwise?
Try converting the audio file to 48 kHz (standard video sample rate) The file you recorded was probably running at 44.1 kHz (standard audio CD sample rate) which would cause the sound recording to run longer because the it was recorded at a slightly slower rate.
I am having the same problem as Craig using a Marantz solid state recorder and hooking it up to video shot in 24P on a Cannon XH-A1. We were having the audio go out of sync about a full second every 30 seconds, so we switched the Marantz to 48khz. This worked well in our test run (which was about 3 min of video). We then shot a full length interview, about an hour’s worth of video, and noticed that by about 5 minutes in the audio was visible off. In other words, shifting from 44.1 to 48 helped considerably, but we are still having issues. Thoughts?
Firstly, Make the start timecode of your sequence 00:00:00:00 If you lay the video and audio on the timeline from your in sync mark, go to the end of the timeline, find a sync point on the video and audio, cut the clips and delete the ends that you’ve just cut off. The audio and video will be at different positions on the timeline. Make a note of the timecode at the end of the video clip which will be the duration of the clip if you’ve made the start timecode all zeroes.
Select the audio clip, cmd-j and enter the duration of the video in the clip duration box. Fcp will then adjust the speed of the audio so that it’s the same duration as hd video. Then drag out the end of the audio and video and it should all be in sync. Check at various point in the clip just to be sure.
Sounds more complicated than it is.
Great article. Thank you.
I have a question (or two). How do I eliminate the in-camera sound before I merge the clip?
See, when I set my in points for the audio track and video, the merged clip now has 2 stereo tracks (the in-camera and the recorded audio).
Oh, and one more thing. How do I back up merged clips? Thank you.
Thanks so much for that tip! It worked great.
Laura
I believe there’s a question that was asked by both “Nikki Draper” and “Kareem” that was never answered.
The question is “How do I get rid of the attached camera audio?”. I am also wondering about this question. The only option that I can see where you can take off the audio is under “clip settings” but for some reason the options are only available after you make your clips “offline”. I’ve tried offlining the clips, taking off audio in clip settings, then relinking, but when I reconnect the media the audio comes back.
Any suggestions?
Much appreciated!
You could turn off the audio capture if you’re digitising off tape.
You could open the video clip in QuickTime 7 and I think cmd-j will bring up the properties box and you can delete the audio tracks there.
You can not remove the audio from the camera in the merge clip that I know of. When you edit, just have track 1 and track 2 little link button on the timeline unlinked so when you edit the camera tracks won’t appear in the sequence.
My question is, let’s say I edit my sequence with Merge clips using the audio from 1 source and Proxy video, then when I’m done I want to replace the proxy video with the HD video? Also what if I edit the merge clips and then afterwards I sweetened the audio in another program then I want the merge clip to read the new audio?
Or just hold alt, select and delete.