Video/Audio Sync Delay

[Darin Steffl]

What is the best way to tune video/audio sync to avoid delay between the two. We have an NEC 1200c, GDC SR-1000, and Dolby CP950 and I feel like the audio and video isn't perfectly in sync.

Are there any good test DCP's out there that can help me tune this properly? I'm new to the Cinema world and am learning tons.

The default global audio delay on our CP950 is 80ms. The GDC audio offset is at 0ms and I can adjust to +200ms or -251ms

Thank you

[Harold Hallikainen]

A Sync Flash Pop DCP is available at http://ftp.uslinc.com/Products/LSS-2...t%20(cropped)/ .

Harold

[John Thomas]

For iOS, there is an app called Catchin Sync, link here: https://quietart.co.nz/catchinsync/

Be sure to calibrate for your device using the website's provided adjustments, and check it for yourself by dropping a bouncy object on the table right in front of your camera's lens (you should get a ~0ms offset).

There are a number of dedicated devices for this specific purpose that may be more accurate, but they cost more money than an iPhone app. Another benefit of the iPhone app is, like I said, you can real-world check your calibration quite easily.

You can use it in cinema with any sync pop DCP. You can use it in production as well -- a person claps a few times on camera and you set the audio delay so that there is 0ms offset between audio monitoring and video monitoring. ANY tool that eliminates the "a little to the left, no a little to the right" types of conversations between techs, producers, customers, etc. is worth its weight in gold.

[Marcel Birgelen]

There are a few devices that can measure the delay in exact milliseconds, but a poor-mans solution is to make a video of a flash/pop reel or DCP in the reference position of the room, for which you want the delay to be ~0ms.

I load the video into my favorite video editor and determine the offset between the pop and the flash. Most video-editors will have some simple tools to show you the offset, otherwise, you simply count the frames and multiply that by the framerate divided by one.

Keep in mind what you want to choose as zero-position in the room, if you have a large room, you want to divide your "delay budget" as optimal as possible.

[Leo Enticknap]

The definition of "large" here being the distance from the front row of seats to the back. If that's more than 30-40ft or so, you won't be able to achieve sync that appears razor sharp to a discerning viewer sitting anywhere. A school of thought holds that the best bet is to set it for a point toward the front of the house, because sound ahead of the pix is more likely to be perceived as a defect to your average viewer than sound behind.

In terms of what is the best way to set it, the crucial question is whether the sync delay is global to all playback sources, or is different for DCP playback relative to the other sources going into the 950. If it's roughly the same for everything, I'd set a global delay in the 950. If it seems to be different for DCP playback, I'd set it in the SR-1000. The 950 also allows you to set a different delay for each macro, but I'd be cagey about that, because if another macro is created quickly, e.g. for a special event, the risk exists of forgetting to copy that setting over.