recording sound for film to be transfered to video.

[Captain Mench]

Keep in mind that there aren’t frames in Sound. Only samples per second for digital.

One second of sound will be one second of sound regardless of what your frame rate is going to be.

Good luck,

CaptM

[Daryl K davis]

Not entirely correct. DAT recorders use framerates with timecode, so audio recorded on location can in fact be measured in frames. It is the audio timecode that is sent to the slate for syncing and tracking audio timecode.

[Arnie Schlissel]

If the camera has a crystal sync setting for 23.976fps, then you don’t need to do anything special. If it only has a sync setting for 24fps, then you need to slow the audio down by .1% before syncing in post. The lab that does the transfer may be able to do this for you, or the sound recordist may be able to.

Arnie
https://www.arniepix.com

[Captain Mench]

Interesting… Thanks. Didn’t know.

CaptM

[Wang Lee]

Thanks CaptM, Let me see if I follow you. I shoot the film at 24 fps. I record on a time code DAT at 30 fps. The lab will make a Time code transfer with a 3:2 pull down 30 fps for video editing, and since my audio is recorded with time code running at 30 fps it should retain sync once the film is on tape and I just sync the two?

[Captain Mench]

Sorry — I’m backing out of this thread… I’ve never recorded to DAT synced to video before so I’m in over my head.

Help is on it’s way I’m sure.

Good luck,

CaptM

[Tony]

Wang the rule is as follows

If you shoot at 24.00 on camera then audio recorder needs to be at 30.00 NDF
In telecine the film will be played back at 23.98 for the xfer to tape at 29.97. Audio will be slowed down to match
Shoot a smart slate with visual timecode displayed and you can sync up the audio yourself in in FCP.

You must make sure however that you have sufficient preroll on the DAT audio recorder before you drop in the visual slate.

IE 5 seconds of preroll then drop in visual slate for 1 sec clap sticks and call action.

If you drop in slate before preroll has been established you run the risk of having problems later locking up the DAT playback machine.

Of course if your record to hard drive for audio this will be a different story.

Note in HD where the camera or recorder can be set to 23.98 you would set the audio recorder to 29.97 to match the 23.98 frame rate on the HD camcorder or HD vtr.

In anycase the formula is quite simple.

Camera rate external audio recorder frame rate

23.98 equals 29.97 Non drop frame for both camera and audio (fyi DF does not exist in 23.98 or 24P)
24.00 equals 30.00 Non drop frame for both camera and audio

Good luck,

Tony Salgado

[Wang Lee]

Thanks for everyones help. I think i’ve got it.
Wang Lee

[Steven Gonzales]

The most common way for sound on dat to be slowed down is to record with a 30fps clock (usually the Dat’s internal clock is used), and then when the audio is put to video, a video sync is used as a clock to the playback dat player, and this results in slowing down the dat by 1/10th of 1 percent.

Another way Dat is slowed down is by sample rate. The Dat is recorded at 48,048 samples per second. When it is synced to video, it is played back at 48,000 samples per second, thus slowing it down.

Another option is to edit at 24 fps in the edit machine, and match the sound sync there, and then no adjustment is needed in sound speed, as the film (which was slowed down when put to video), is sped back up when converted to 24fps, and now matches the original sound speed.

However, if you bring the film in to your edit system at 23.976 fps, you would have to also adjust the production audio to match, by slowing it down by 1/10th of 1 percent.

People often confuse the clock source with the address source (timecode). Timecode does not determine the recording rate or the playback rate. Those rates are a function of the clock source and the sample rate.

A final option is conforming the audio to another sample rate through software. If you record at 48,000 samples per second, and tell this file to playback at 47952 samples per second, it will take longer to complete the samples (in other words, slowed down) by 1/10 of 1 percent.

[Wang Lee]

Thanks Steven,
That gives me a number of options.
Wayne