(Auto)Sync Guide

Many productions use double system audio workflows due to the low quality inputs on DSLR cameras or for the flexibility and higher bit rate quality available to dedicated production audio recorders.  In those scenarios, a syncing process is done either in a third party dailies system or within Media Composer itself. There are multiple ways to sync picture and sound in Media Composer:

  1. Both picture and sound elements have common timecode. This is the easiest and fastest way to sync as you can do the entire day’s dailies in one batch process. 
  2. The picture and sound elements have easy to see and hear slate and clap but no timecode. This involves marking a Sync point on the slate and clap and syncing one take at a time. 
  3. No slate, not timecode and all hell breaking loose. This type of syncing is usually done via the timeline where both elements can be slipped as needed to be in sync and played back to confirm. This is also the process if using PluralEyes to sync based on waveforms. 

For further sync accuracy, it is common to work in a 35mm film project so that sync can be slipped on 1/4 frame increments. You can read why I use film projects on digital camera workflows here.

Media Composer v7 brought new functionality that brings new workflows to the product - namely Color Transform (source side LUT) and Image Transform (FrameFlex). But… Keeping the flexibility of linked AMA, LUTs, and FrameFlex with double system audio workflows can be a bit of a minefield. Understanding what can be synced and 1/4 frame slipped with these functions before you start and workflow is important to know. In some cases, the production will have to decide what is more important; color management, quality image extraction or accuracy of sync with double system workflows.

The following  two images show the results of double system workflows with a total of 42 total combinations of 7 source clip types. The NAME in the bin starts with how the clip was created:

  • Picture AMA Linked
  • Picture Transcode from AMA link
  • Picture via Avid’s Dynamic Media Folder feature
  • Picture via a third party dailies system like Resolve, Colorfront, MTI Cortex, etc.  
  • Audio (BWF) via AMA link
  • Audio (BWF) via transcode from AMA link
  • Audio (BWF) import

For picture transcoding, there is an additional set of files that include compatibility mode ON or OFF for either Color or Image transforms (or both). This covers most, if not all the methods by which picture and sound essence can be created. Then, there are the two methods of syncing as mentioned resulting in 21×2 resulting sync clips. I have to admit this took a bit of time to create and keep track of, but the information is good to know before realizing too late that a particular method won’t work after spending all the time with a transcode process.

Each method is in its own bin; one for syncing clips in the bin and the other via the timeline. The clip I used was a typical DSLR type clip that did not have common timecode, but a clean slate and clap. The clip was VA1A2 as recorded in camera (scratch audio) and the BWF were 8 track polyphonic with MIX track on A1. The resulting VA1 .sync clip was a result of the options in the AutoSync dialog window to remove audio from video, and keep A1 from BWF. The project type is 1080p/23.976 and 35mm/4 perf active. 

In the first case, syncing the clips directly in the bin two at a time will always sync (as compared to the timeline method), but only the imported BWF audio was able to be 1/4 frame slipped for more accurate sync. All other combinations will not 1/4 frame slip. Green clips are 1/4 frame synced, Red clips are not. Click on thumbnail for full bin view with comments. The columns will indicate ability to sync and to 1/4 frame sync as separate processes. For each case where sync or 1/4 frame slip could be performed, the error message is listed. 

syncing-from-bin.jpg

In the case of timeline syncing, the results are a bit more of a mis-mash. In some cases you can sync and 1/4 frame slip, and in other just sync, and with some, nothing at all.

syncing-from-timeline.jpg

As seen with these results, in order to have 1/4 frame slip capabilities, the picture needs to be transcoded with no active image or color transforms applied. This means one needs to choose which is more important to the workflow in this stage of the process.  This is more or less handled by syncing clips from the bin, but for productions needing to use PluralEyes or have no slate/clap on their dailies and must sync via a timeline, their options are much more limited.  So be sure to plan ahead!

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