Sync HD & Black burst

[geoffrey.mix.that]

Can Sync HD handle 96 khz black burst signal? cuz I'm going to record a concert under 24bit/ 96khz, and want my audio and video synced to frame accurate. thanks

[Postman]

You can do this. "Black burst" is a standard video reference signal that defines the VIDEO frame rate. It is the same video reference signal no matter what sample rate you operate Pro Tools at. While SyncHD is locked to a black burst signal it will ensure that your PT audio hardware is time-locked to the video reference.

[geoffrey.mix.that]

Thanks for the info , Postman, So, it doesn't matter what sample rate black burst is , right? cuz, I don't have sync hd to test it before recording date, but I thought when I choose Video Ref as the master clock , the session must follow it ....??!!

Originally Posted by Postman

You can do this. "Black burst" is a standard video reference signal that defines the VIDEO frame rate. It is the same video reference signal no matter what sample rate you operate Pro Tools at. While SyncHD is locked to a black burst signal it will ensure that your PT audio hardware is time-locked to the video reference.

[Chief Technician]

Originally Posted by geoffrey.mix.that

Thanks for the info , Postman, So, it doesn't matter what sample rate black burst is , right? cuz, I don't have sync hd to test it before recording date, but I thought when I choose Video Ref as the master clock , the session must follow it ....??!!

I am not Postman, though I do have the answer.

Black burst operates at a frame rate. The frame rate of the black burst will be determined by the frame rate the videographer uses for the recording. Possible frame rates are:

• 23.976 (aka 23.98)
• 24 - If someone says "24", ask them if they really mean "24". Some people wrongly say "24" when they really mean "23.98" or "23.976".
• 25
• 29.97
• 30
• 47.952 (aka 47.96)
• 48
• 50
• 59.94
• 60

Once you patch the black burst to the video ref input on the SYNC|HD (don't forget the terminator on the video ref loop output), select the appropriate frame rate in the Session Setup window, then set your sample rate. You will have NEAR sample-accurate lock to the black burst?

Why NEAR sample accuracy? Some of the black burst frame rates listed above are not evenly divisible by a given sample rate.

[Postman]

^^^^^

but I thought when I choose Video Ref as the master clock , the session must follow it ....

"Sample rate" and "frame rate" are fundamentally independent. SyncIO has independent settings for audio sample rate, session frame rate, and video reference frame rate. Sample rate is defined by your session, the other two are defined in the session setup window.

Here's a quick review of the basics

For us, sample rate is the speed at which your audio hardware converts between analog and digital worlds. Video picture uses "frame rate" (standard ones are listed above), which is the number of still images per second a camera records a real time image. The only relationship these two rates have to each other is they both use seconds as a timebase. Samples per second of audio. Frames per second of video.

Your session determines the sample rate. In the session setup window you can select any of the standard frame rates, which does NOT change the sample rate. Video determines the frame rate. Audio does not care what the frame rate selection is because audio sample rate is not affected.

In your session settings window you can tell SyncIO which type of video reference signal will be applied to it. SyncIO will be able to lock onto that signal and determine how long exactly a second is (relative to the video). It then operates its sample rate clock to output the exact sample rate clock to fit the video signal. Again, the number of samples per second, the sample rate, is determined by your session. The video frame rate is determined by the video in use and the selections you make in the session setup window. Making them actually operate with a near-perfect relationship is ensured by SyncIO (with selections you make).

I noted earlier that there are separate settings for session frame rate and video reference frame rate. Often these are set the same but they do not have to be. For example, it is possible to view and work with 23.976 frames per second video in your session while using a 29.97 frames per second video reference. In such a case, the session's frame rate would be set at 23.976 while SyncIO's video reference setting would be 29.97 or NTSC. This had been a common workflow during the transition from SD to HD video.

One other interesting detail is that the standard audio sample rate for ALL broadcast and theatrical presentation has been 48kHz, no matter with the frame rate is. There is nothing wrong with working at 96kHz. Perhaps you will be able to keep 96 all the way through a Bluray release, but for many uses it will need to be converted to 48Khz.

I hope this is helpful.

[Peter Baird]

Originally Posted by Postman

"Sample rate" and "frame rate" are fundamentally independent.

It wasn't always that way. (Shudder.) Took a little while for chips to come along that could do all the math. And we used to make it really hard on ourselves by using 30 frame resolve for music production (PCM1630 anyone?) and 29.97 for video. Caused quite a few tantrums back in the days of capstans and pinch rollers.

Peter