Are TC Slates Used Primarily for Frame-Accurate Sync or as a General TC Reference?

[Karl Lee]

TC slates are fairly common on video and film projects big and small nowadays, and I had long assumed that use of the TC slate was a fairly integral part of synchronizing audio and video in a timecode-based double-system audio recording configuration. However, I've been researching and learning more about TC-enabled audio recorders recently and have come up with a few questions, so hopefully someone can help.

 

I had assumed that file-based, TC-enabled pro audio recorders kept some sort of running TC track for the duration of a recording (as did TC-enabled DAT recorders, for example). However, from what I've found (and someone please correct me if I'm wrong), it looks like most TC-enabled file-based audio recorders (even high-end, pro models) don't keep a running TC "track", but rather just timestamp the first sample of audio. BWF files, for example, note a single timestamp at the beginning of the recording and write the single timestamp to the file's metadata. I'm not sure if BWF files are the most common file format for pro audio recorders, but my understanding is that for most file-based pro audio recording systems, TC is stamped in this manner...a single timestamp noting the beginning of the clip as opposed to a continuous, running TC track to accompany the audio recording.

 

I believe most pro NLEs can be set up to detect the TC timestamp from the audio file's metatata when imported, but that's just a reference point for the first sample of the audio file. Any subsequent timecode for the audio clip is essentially calculated by the NLE, using the single timestamp as a starting reference point. While I imagine the NLE's calculated TC values are fairly accurate, I'm guessing that the calculated TC for an audio clip might not be as accurate as if there was a separate, dedicated timecode track providing TC marks throughout the clip, particularly for longer audio clips.

 

Anyway, back to my original question. Considering that even pro, file-based audio recorders may not record a dedicated TC track and that NLEs end up generating an audio clip's TC based on a single timestamp in the file's metadata, are TC slates typically used used specifically as a frame-accurate synchronization method to sync audio and video tracks in post, or are they used primarily as a general, visual reference to help match up a video or film take with the correct audio file?

 

Even with TC slates, it seems like the slate's sticks are also used, so the comparatively old fashioned use of the sticks may prove to be a helpful sync point after all!