Sending word clock to camera from sound device 722

Question

I am interested in understanding the concept of sending word clock from a sound device 722 to camera (Arri Alexa and Nikon D800). What we are planning on doing is sending a reference from the sound device to the cameras, either dialogue or potentially word clock so that in post, we can sync up the dialogue on de vinci and FCP using the dual eyes program. We are doing this because the issues that we had in the past were that that the editors were using camera sound to edit with and not the sound device recordings, making it very difficult for the sound editors to source exactly what clips would go with what images.

To solve this issue, we would go with a wireless set up, sending the dialogue to the camera as strictly a reference track so that camera sound would not be an issue anymore. The other alternative would be to send a word clock signal to the camera as an alternative to timecode.

My question is will sending a word clock signal to the camera solve our problem of people relying on camera sound instead of using the actual recorded takes from the sound device. I know that word clock is a bit rate/sample rate syncing device but will this concept work as a reference track?

I hope this is clear as I am a little fuzzy about this as I have never done it before. Always used timecode in the past.

Thank you. Hope it isn't a stupid question.

Answer 1

Wordclock and timecode are different things. Wordclock sync is basically just making sure that 48K on the master is 48K on the slave device. It doesn't have any positional reference. It is good to have everything locked to a wordclock or black burst master no matter what type of work you are doing to avoid clocking errors between equipment and to prevent drift on longer recordings.

Answer 2

In addition to the response from coaxmw :

The bandwidth of a word clock signal is much higher than an audio signal, which means you cannot transmit a word clock over an audio wireless system, neither record it on an audio track.

One possible workflow for your case is to resync all clips with the audio from the audio recorder prior to editing, which is transparent for the picture editor.

One way to achieve this is to record the audio on the camera as a reference track and use a software like plural eyes to automate the sync process.

Another way to achieve this is to record time code generated from the audio recorder on the camera audio track. Some editing software have an option when importing video clips to designate a track as time code track, which will then be synced with the time coded audio tracks from the audio recorder.

Notice that due to the fact that your camera and audio recorder are not sharing a common clock, you might have issues of not perfect sync in the case of long takes (several minutes).