How to Avoid Timeline Chaos in Avid and Premiere With Sync Locks

Sync Locks are training wheels. You need to master your timeline

Anonymous Avid Editor

The Situation

I’m cutting a film and we are close to having the director’s cut completed. It’s 105 minutes long and fairly complex: I’m using Avid Media Composer because of its unmatched power when it comes to collaborative projects. I have 26 tracks of audio and 5 tracks of video in my timeline. The first and last scenes have both specifically got a lot of audio and video tracks, as do some of the scenes in the middle of the film.

The director wants to change a scene in the middle of the film, one of the complex ones. This scene has dialog, SFX, buzzes and a couple of music tracks that correspond to specific hit points in the film. The director wants to add in a few shots and extend the montage part of this scene.

There are a number of ways to do this, but of course, the main thing you need to do is keep everything else in the right place. You can’t afford to start trimming in the middle of your cut willy-nilly if you’re not 100% sure that everything else in your timeline is going to be where you want it to be. That’s where “Sync Lock” comes in.

What exactly is a sync lock?

In the early days of non-linear editing, the systems were designed to emulate a flatbed for film editing. The tracks were all ‘unlocked’. In other words, if you were adding or removing time, you had to make sure you were doing it across all the tracks you wanted to adjust. If you only had your video track selected and you deleted some time, it would only affect your video layer, bumping everything else out of sync.

Sync locks allow you to lock certain tracks together in order to keep them in sync with each other. Some NLE systems do this automatically, like the magnetic timeline in FCP X, but there are plenty of occasions where you don’t want them locked together.

In Media Composer and Adobe Premiere Pro, you can also LOCK your actual tracks which prevents them from moving when you’re trimming. This essentially is the opposite of a sync lock: sync lock will lock tracks to each other so they will move with each other. Locking tracks will prevent them from moving while you move everything else.

The first NLE I used was a Lightworks with four (yes, 4) audio tracks and one (1) video track. We used to love doing three-way dissolves by doing a dissolve in the NLE, playing that dissolve to U-matic tape and digitizing it again so we could dissolve from that digitized ‘thing’ to a new shot. One editor I assisted used to actually name his clips ‘thing’, on the NLE, making my life as an assistant quite tricky. (I think there was something wrong with me because I loved working with him!)

I then started using Avid on commercials with a lot more audio and video tracks, but I didn’t use the sync lock functionality at all. Not because commercial cuts are simple—far from it—but because they’re short enough that you can see what you need at a glance.

Also, a lot of TV commercials are music-driven, and the length is strictly adhered to. So often you put down elements that you want to keep in place: music, VO and titles are some examples. Unlike most forms of editing, I prefer those elements to stay in place while I trim the others, and I never want them to move.

A commercial timeline might look like this:

As you can see, some of the items need to stay where they are. The music must be 60 sec long (often it’s a pilot track that’s already been composed to the correct duration), the end title has to be 3 seconds long, and the packshot and title has to come over that. But the sound effects and dialogue are specific to the shots that I’ve placed them with. I want those to stay in sync with their clips. So in this example, I’d work with a Media Composer timeline that looks like this:

In the early days of Avid, I don’t think there even were sync locks, but, if there were, the default was for them to be switched off (this has now changed).

If you wanted to use Trim Mode to trim a cut point, you had to make sure you selected all the correct trim points to keep everything where you wanted it. Here’s a trim with Sync Locks OFF.

In the above screenshot, I had to manually select all the tracks that I wanted to move and make sure I had a trim roller on each one so that they stay in sync with the actual shots I was trimming.

In Media Composer, if I do the same trim with Sync Locks ON, the NLE will give me ghost rollers on the tracks with Sync Lock, like this:

Trimming like this involves a lot less clicking and a lot less decision-making. You just trim where you want to and everything stays in sync that you want to stay in sync while everything else stays in place exactly where you want it.

What all editors would argue for, when defending their own choice of NLE (and their own preference of using sync locks), is the need to be able to make changes to the cut, quickly and intuitively, without having to think too much about which button to press or how to go about achieving the desired result.

This really amounts to muscle memory and a familiarity with the content, but when your projects get big and complicated, you really need to be master of your entire timeline.

Staying in Sync: Sync Locks on

This is my default way of working at the moment, and probably a very familiar one for most editors.

I’m working in Premiere on a mockumentary with episodes of approximately 25 minutes. Not the longest thing I’ve ever worked on, but long enough and complicated enough that I will have some scenes down the line where I want all the video to stay in time with the music and sound effects that I’ve carefully placed. Also, certainly not 24+ audio tracks, but it’s enough to have to keep track of what’s being affected downstream while I tweak somewhere in the middle.

My Premiere timeline might look like this:

Close up, I may have a scene like this, somewhere in the middle of the episode:

The director wants to add a few shots to the middle of the scene. I’ll probably add the shots first, then come back and tighten.

If I simply insert the new shot, what happens to my music? Obviously, it gets a hole in it, which makes a quick playback of these new shots impossible. Dealing with this is easy:

I simply move the music tracks down to the lowest track (19) which I always keep empty (In Premiere this is easy- Alt+down arrow).

I lock this track so that my music is unaffected, then work on the cut, adding and trimming until the director is happy. Before I move on, I may have to fix the music edit because it’s probably not ending in the right place. In this case I simply take the existing end and move it later, then backtime that cut point. You can see that there is a part of the music which is going to repeat, but for now I at least have continuous music. The alternate is to lock everything else except the music and work on the music edit then put it back in place, higher up in the tracks. I have shortcuts for locking all video tracks or locking all audio tracks to save clicking, but you can also SHIFT+click one of the lock icons to lock/unlock all tracks.

So far, so good. There are a few variations on this, but I find that’s the most common way I do it.

In Premiere I have another similar option: I can switch off sync locks on track 18 instead of locking the track. The sync lock icon is next to the track light indicator). This will allow me to work on the rest of the cut without affecting the music. Mostly I use insert edits to get the shots into place, then Ripple Trim on a shortcut to quickly start or end a shot on the exact frame I’m parked on, followed by trim mode where I will loop the cut point to optimize it.

The problem with using this method in Premiere is that when I trim the sequence of shots, I must use TRIM MODE but can’t use Top and Tail, otherwise some music is also deleted. And when I come back to fix the music, all the other tracks are affected when I try to use trim mode or insert/ delete. Not very elegant.

On Media Composer this is a little easier for me in some ways. Here’s a timeline of a short film I worked on.

I always work with some unlocked tracks at the bottom of the timeline and use dummy timecode tracks to visually separate the sections. They’re a combination of mono and stereo because in MC, you can’t put mono audio onto a stereo track or vice-versa.

When I need to make changes to a scene, I drop the music/sfx down to these tracks to keep the clips from moving out of sync. Cutting and trimming is the same, but when it comes to fixing the music, I can simply deselect all the other tracks and cut the music without affecting anything else. I really like being able to do music using trim mode, so this works well for me.

(Note that the latest version of Media Composer now has a keyboard shortcut to move clips up or down one track, but in past versions you had to hold SHIFT +Cmd as you dragged the clip down or up).

Here’s how I do it in Media Composer

How to switch them off

You can switch sync lock on for one track at a time or switch them off all at once, as follows.

  • Avid: Click the sync lock icon to the left of the Solo/Mute buttons. To select/deselect all, just click in the sync lock column on any timecode track.
  • Premiere: Click the sync lock icon to the left of the mute button. To select/ deselect them all, Shift+click the icon on any track.

Sticking with an example from Media Composer, let’s say I have a scene that looks like this:

If I want to make adjustments at the playhead, I want certain elements to move to the right and certain elements to move to the left. I can’t just delete or add because all of my sound will end up needing to be fixed.

With sync locks on, if I go into Trim Mode I will get this:

If I drag or use a shortcut to add frames, all of those points will move to the right and mess up my sync. Media Composer will also try to keep things in sync so I’ll end up with gaps in some of the tracks.

A few ways you can trim on one side in MC (this is similar to the way you might trim in other NLEs):

Asymmetrical trimming (Media Composer only)

With sync locks off, however, I have the flexibility to choose which side of every edit point I’d like to trim. Combined with Avid’s Asymmetrical trimming, I can not only manually select the trim points for each track, but I can choose a different side of each point to trim. For example, I want to trim the clip on v1 shorter, i.e. to the left.

Here’s what my trim might look like:

When I make adjustments, the trim will always use the first point I created as the trim. So to create this trim I started by clicking to the left of V1,  then to the right of A1-5, to the left of the out point of A7-12, to the right of the cut in A13-14, in the black on A15-A16 and to the left of various points on A17-A20.

When I press the key to trim back 10 frames, everything with a roller on the LEFT will shorten the END of the shot by 10 frames, but everything with a roller on the on the RIGHT will shorten the FRONT of the shot by 10 frames.

As with all trim modes, you can use the spacebar to loop and review. Just remember that Media Composer will use the first point you chose as the point to loop from and the point to delete from or add to. (This has changed from earlier versions of Avid where it was the last point that you clicked).

Note that this Asymmetrical Trimming is unique to Avid. Other NLE’s have a Trim Mode where you can select a bunch of edit points and trim to the left or the right of them but I have come across nothing even close to this ability in an NLE. (Not since that 4-track Lightworks I used in 1996!)

Also note that this Asymmetrical Trimming does not only work with sync locks off. You can use it with them on, but a lot of automatic choices are made for you, all on one side of the cut, so sometimes it takes a few extra clicks to override the default placement of the rollers and choose exactly where you want the rollers to go. Some editors seem to prefer sync locks off, referring to them as training wheels but others feel they give far greater confidence.

Redoing a Trim

So I’m trimming like a boss, but the playback/review loop is only 2 seconds long and I need to check that this trim works somewhere else in the timeline. I exit trim mode and play the scene. Wait a minute, something’s wrong at one of the other points and I need to redo that trim. I suppose I just have to go through that process again: click-click-click the different sides of the cut points to trim. Wrong!

This little tip is probably one of the most powerful and least-known shortcuts in the whole of Media Composer world: you can always get back your exact last trim by pressing Alt+Trim Mode.

When I discovered this, my life changed for the better: my work days got shorter, summer arrived, I met a nice girl and I got rich. Well maybe not, but it did change the way I started using trim mode. It made me more effective in the edit room and gave me confidence to really master my timelines.

Other useful tricks

I’ve come across a few other ways of keeping those tricky timelines in sync. These can be used with sync locks on or off, in Avid or in Premiere. There are variations in each NLE, but the principle is the same. I’ll cover the most simple of keystrokes but reading the manual or watching online tutorials specific to your NLE will really help.


In the example I used earlier, shown here again, you could also do the following:

  • Insert new shots and obviously add gaps
  • Use the Extend function to fix the gaps. In Media Composer this is done by marking an OUT point where you want your clips extended to, selecting the tracks you want to affect and pressing the Extend Symbol.
  • In Premiere Pro this is called Extend Selected Edit to Playhead and works by parking the playhead at the newly desired edit point, (i.e. where you will want the clip to extend to), selecting the end of the clip you want to extend and pressing E.

With a bit of practice, you can create very fast seamless cuts for preview. These might not be perfect but in the case of sfx, buzz tracks and music, they are quite effective. This can be used to extend forwards or backward so it’s pretty useful.

Select Right, or Add Filler as keyboard command

FCP7 and Premiere users will no doubt be familiar with the Select Right command. You can select all clips to the right or left of the cursor on that specific track or on all tracks, depending on your keystroke. I never really use the Select Left command but that’s possibly just me. But I do use the Select Right command (A) to grab all clips to the right of my playhead, possibly manually Shift+clicking a couple more, moving them down by 30 sec and then working on the offending section of the cut. When I’m happy I do a similar thing to pull them back into place.

In this example, I used a little bit of asymmetrical trimming to get things back in order but only because that struck me as the quickest way in that situation. In Premiere I would have had to do a little more dragging.

A quick note that in Media Composer you need to make sure you switch off the checkbox for Select Filler with Segment Tools in your timeline settings. Long-time Avid users will remember all too well how the segment tools used to also select all the empty filler between tracks.

Add Edits (Media Composer only)

In Media Composer you can add edits (aka through-edits) in the black slugs, so you could find a section of your cut that’s relatively clear and Add Edits across all tracks (in one keystroke). You’ll then be able to make sure that you notice when something goes out of sync.

Add Markers as sync points (Media Composer only)

Similarly, you can also add markers to the filler between clips as well as to clips themselves in the timeline (those bits of filler do have their uses!), thus giving a reliable way to check everything is in sync. The downside to this is that you have to add all the markers one-by-one so if you have a lot of tracks this will take a while (even with a macro this would be cumbersome).

Add Tail Leader

Furthermore, it’s not very commonly used, but you can actually add tail leader in Media Composer. I’ve seen some editors use this as a way of double-checking sync, I guess by ensuring that all the clips end where they should.

You need to have filler (i.e. no clip) in your uppermost video track at the end of your sequence. Then activate the uppermost video track and turn your sync locks off. Park at the end of the sequence and press the Add Edit button, then go into Trim Mode.

Deselecting Linked Selection (Premiere)

A lot of video is imported into the NLE with the attached audio, whether that audio was recorded straight to camera or as separate WAV files on set and synced up later. So when you cut these into the timeline, they’ll probably have audio with them which you may or may not want to use. Mostly if it’s dialogue you will want to keep it with the clip, but it’s very easy to separate the video from the audio by deselecting the Linked Selection button in Premiere. This is handy if you want to grab and move clips around without their corresponding audio. There’s a nice little sync indicator to show you when you go out of sync and it’s very easy to move, or slip, the video or audio back into place by right-clicking on the red numbers that you get.

In Media Composer there is a button for Linked Selection Toggle above the Red Segment Mode tool. This also shows you how far you are out of sync, but it doesn’t give you the option restore the sync at a keystroke.

Also, this method doesn’t really help with the audio you’ve laid yourself like sfx and music but maybe that’s what you need sometimes.


The methods above are all fairly straightforward and you probably have used some or all of them at one point or another. I rarely cut without sync locks these days as I find it gives me the best combination of speed and reliability. I rarely have to stop the session so I can figure out why one track is out of sync and why. And I haven’t heard the words “Why is this taking so long?” in many years.

What are some of the tricks and tips you’ve picked up over the years to keep your complicated timelines in sync?

Richard Starkey

Richard Starkey has spent 26 years in the film industry, working on a wide range of genres including high-end TV commercials, feature films, music videos, TV drama and documentaries. He is primarily an offline editor but also loves to grade and teach. He lives in Cape Town, South Africa and when not working you'll find him on the squash court.