The importance of blackburst sync in audio post?

[DigiDB]

Hi Jsalam112,

The SYNC box is a stable SMPTE/word clock generator...as long as it has a stable reference.

The internal crystal is VERY stable...as most are.

REAL BASIC STUFF YOU PROBABLY KNOW, BUT...

The things to remember about this stuff is:

There are two "parts" to the scenario:

1 - Clock - the speed that audio is played/recorded.
If you have common clocks throughout your workflow, everything will line up.
If you DON"T have common clocks, you'll get audio running at different speeds...in relation
to other audio, or in relation to picture...what's called "drift".
2 - Frame rate/timecode - basically a "frame numbering" method.
If these match up, the numbers all match and you have no or a "zero" offset.
If they're different, then you have a positive or negative offset...and they run at the correct
speed, just not at the correct location.

Fixing or compensating for an offset is a bit easier than fixing or compensating for "drift".

If you don't have a clock at all...for a capture, on the set, during a transfer...that's when it gets expensive. You either have to "hand sync" it (basically "fake" sync), or redo the step.

The good thing about video reference is that it's usually the common "clock" throughout a video workflow.

The only downside about using a video signal from a deck is that, depending on the deck, it's not always consistent...some decks don't put out "good" video when they're stopped, some have "bad" edits, etc.

Black burst is a stable, continuous video signal at a (hopefully) broadcast standard.

Again, all the other advice is good...just remember the basics...same clock, good. Different or missing clock...bad

Although I've never tried it, theoretically, you can use the word clock out of the SYNC (or other Digidesign peripheral) for reference on the DA88 (same clock!).

[Chief Technician]

DigiDB,

Thanks for chiming in on this thread. The one question that I can't answer for Turbosynth, that I'm hoping you can, is this.

If my system reference is blackburst, and then I switch to internal/vso, and I don't do any pull-up/down in the process, does audio then get pulled up by changing the clock reference? If I record audio reference to blackburst, and play that audio back referenced to internal/vso, do I end up playing back my audio at a pull-up rate?

[hell pie]

When a device is running by itself (no other machines in sync), it can run on its internal clock at ANY sample rate and frame rate. There are no other devices running in sync, hence no need for a common clock. If Pro Tools is running by itself (no other machines in sync), changing from video reference (blackburst) to internal sync will not affect the sample rate. The audio will not be pulled up or pulled down.

[TVPostSound]

If Pro Tools is running by itself (no other machines in sync), changing from video reference (blackburst) to internal sync will not affect the sample rate. The audio will not be pulled up or pulled down.

Only if there is an audio file in the timeline to regulate the internal sync.

Once Protools records a file with blackburst, the file's sample rate is now the clock.
A Protools system running on internal clock is not running at the same velocity as another Protools system running on internal,
the difference might be very minute but there is a difference.

[110 ohm]

A few years on from the original post...

Just wondering how you guys are currently set up with Blackburst vs. work clock seeing as more and more people are mixing to quicktime / mojo etc.

Also, we are mixing to V1 in our main studio and laying back to MX24 for stems. Wondering if we should clock protools and the mx24 to word clock or video ref. I know the V1 is getting a house sync from our nanosync but there are no moving heads on the V1. Also, I think the nanosync outputs word clock that is referenced to it's internal video Black generator.

I currently sync protools to video ref but the mixers are asking to switch to word clock as it is more precise from what they have heard. Just curious if we can switch to word clock with no tapes involved. Only disk drive based picture (the V1).

Not sure what is better when using v1 as master picture and timecode source.

Thanks,

Jon

[110 ohm]

A few years on from the original post...

Just wondering how you guys are currently set up with Blackburst vs. word clock seeing as more and more people are mixing to quicktime / mojo etc.

Also, we are mixing to V1 in our main studio and laying back to MX24 for stems. Wondering if we should clock protools and the mx24 to word clock or video ref. I know the V1 is getting a house sync from our nanosync but there are no moving heads on the V1. Also, I think the nanosync outputs word clock that is referenced to it's internal video Black generator.

I currently sync protools to video ref but the mixers are asking to switch to word clock as it is more precise from what they have heard. Just curious if we can switch to word clock with no tapes involved. Only disk drive based picture (the V1).

Not sure what is better when using v1 as master picture and timecode source.

Thanks,

Jon