Dual System Sound Sync in FCP July 3, 2008
Posted by ifsstech in 3rd Tier, 4th Tier, Editing, Sound.trackback
One 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.
___
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