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Old April 11th, 2003, 05:56 PM   #1
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Sync slate uses with DV format

Hi All,

I was recently watching some behind the scenes footage of Star Wars "Attack of the Clones" and noticed that although they shot that movie entirely in a digital video format, they still found it necessary to strike the sticks of their camera slate together before rolling each take, as if it was still necessary to syncronize the sound to the picture as you would when shooting film. At first I thought maybe they did it because of a mixture of habit and tradition, but then began to consider if there was trully a technical reason for it.

Does anyone have any speculation or knowledge as to why a sync slate would need to be used for video or DV formats? I'm very curious...
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Old April 11th, 2003, 06:19 PM   #2
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They were probably recording audio separately, as is commonly the case.
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Old April 11th, 2003, 07:30 PM   #3
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Speaking of this, Ken if you are recording to Minidisc and using the camera for video, how would you sync the two in post during event videography if you didn't record or sync the two devices together. I know, ideally you would start the two together, but what if you wanted to start/stop the camera or had to change tapes or minidisc, woudln't this set your production out of sync? Now how can you sew it back together in post with an NLE?
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Old April 11th, 2003, 08:45 PM   #4
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You move your audio (slip) to match your video with your NLE. It is a simple procedure. It helps to have an aid like a slate or pair of hands clapping.
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Old April 11th, 2003, 10:43 PM   #5
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Garret,
A hand-clap in front of the lens and audible to the mini-disc mic would be enough to provide you with a visual cue and audio waveform spike that you could slip to align as Jeff noted. In Final Cut Pro, for example, you
1. drop the md audio into the timeline below the related video track,
2. turn-on the audio waveform display in the timeline,
3. place the playhead cursor at the hand-clap point in the video, and
4. and then just slide the audio in the timeline until the clap spike aligns with the playhead.

It's best to perform this while using a magnified view of the timeline.
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Old April 12th, 2003, 12:11 AM   #6
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Slate & sticks with video

If you have a slate with sticks, especially with multi-cameras, use the sticks. It sure won't hurt anything. If you have to separate the audio for any reason, it's sure enough easier to use those sticks to sync it again than to eyeball it. One other option is the timecode slate. This is definitely a time saver in post. It's a real expensive way for the camera to see the audio/playback code on set. Pay me now or pay me later. Ha! These can be rented for 50.00 or purchased for around 1500.00. Even though the sticks are not really needed with the time code slate, especially for playback shoots, they are sometimes hit to make slate display the actual point of sync, time of day or as a back up. These slates also have the ability to display freerun code, 24, 29, 30 fps.

www.denecke.com
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Old June 6th, 2003, 10:40 AM   #7
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In this particular case, the location mixer used a Zaxcom Deva to record the sound. They represent the latest in location sound recording technology and are rapidly replacing DAT machines. Time code is sent from the Deva to the slate to provide accurate sync. The actual clapping of the sticks, while not really needed for sync, does four things: 1) Triggers the slate to read time stamp info i.e. time of day or date. This helps keep the takes organized if something happens to the script super's notes. 2) It signals the set that film/tape is rolling 3) it signals the editor that there is in fact sound associated with the take. MOS shots are not clapped. 4) It provides a sync backup if the time code errors. The slate itself also contains a handwritten account (or in the case of the new prototypes a keyboard generated account) for editor. Information like scene, take, frame rate, etc. are always included on the slate.

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Old June 6th, 2003, 11:18 AM   #8
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I do believe they recorded the audio seperate indeed for
Star Wars 2.
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Old June 6th, 2003, 01:25 PM   #9
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Noka...

Last week I did a two-camera shoot with seperate audio of a solo performance. Each song was slated as the audio would be processed seperately from the video and sync'ed later.

I didn't have an authentic slate board but just used a pair of sticks to create a "clapper".

Worked perfectly, and it made synchronizing the two cameras a "snap". Pun intended!

Also found out that the audio track happens to precede the video track by one frame. Don't know if this is intentional or if the video is just slower to get processed. But at a distance of 30 feet both sound and video should be perfectly synchronized as it takes about 1/30 of a second for the sound waves to travel that distance.

Dean Sensui
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