The Basics of Synchronization and Time Code (4)

The Music Telegraph | Text 2019/08/27 [16:42]

The Basics of Synchronization and Time Code (4)

The Music Telegraph| 입력 : 2019/08/27 [16:42]

 

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The Basics of Synchronization and Time Code (4)

 

 

When dealing with video, you must think of two sync signals: "speed" and "location". Where are we (location)? How fast are we going (speed)? When dealing with SMPTE time code in a purely audio world, SMPTE is both speed and location. However, in video, SMPTE is "location" and video sync/house sync defines "speed". 

 

 

In AV editing situations, it has always been important for all video decks and cameras to be "gen locked", which means that their video clocks are all synchronized. They don't always have to be at the same location (which would be addressed by SMPTE Time Code), but they do have to  be frame locked which means that they are moving from one frame to the next in precise synchronization. This is critical for editing video data. As audio people began to do work for video it also became important for them to be synchronized to the exact frames of video.

 

 

Video Sync (also called House Sync or Black Burst)

A reference video signal generated by a very stable source used to precisely synchronize equipment to a specific video frame rate ensuring that multiple machines in a studio are all referenced to one common speed.

 

House Sync runs between all gear that is locked to picture, including video decks, DA-88, DAW, etc. 

 

There are two standard "speed" rates in the world of picture: 60 and 59.94. The 60 speed is used in film applications, and 59.94 is the speed standard for video work. 59.94 is used because it is 0.1% slow from 60, just like the ratio of 30 to 29.97.

 

 

House Sync Generator (or Black Burst Generator)

A box with one or more video outputs, which supply an accurate, and more importantly common, source for the timing of all equipment in the studio.

 

 

What is the difference between House Sync and SMPTE Time Code?

House sync is a video signal containing fixed frequency pulses, and is used as a master clock source in a video system. It provides relative timing information only. 

 

SMPTE Time Code contains address info, allowing machines to arrive at and start from specific points on the tape.

 

 

Word Clock

A common reference signal used to synchronize digital audio.

 

Analogous to House sync for video.

 

Frequency is based on sample rate.

 

Most common sample rates used are 44.1 kHz and 48 kHz.

 

 

 

 

 

 

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