External mattes are out of sync: suggestions?

[Tero Ahlfors]

Do they run at the same frame rate and are they the same length? I’ve never had any issues with just bringing external mattes in. Have you read the manual?

[Michael Mccune]

Tero; thanks for the reply.

Perhaps I was not clear about the fact that the same Fusion clip is imported into Resolve both as a video clip and as a matte.

In the case of the clip imported as video and placed on a track above the original source track, the time code matches at head and tails, so perfectly in sync.

But in the case of the import as an external matte however the time codes–and the visual matte–do not match and are visually out of sync.

So where would the issue of a frame rate difference enter into the process???

Thanks, Mike

[Glenn Sakatch]

what frame rates are you working in. I’m guessing 29.97, as you said it was a 1:07 offset which equals 37 frames…but is that the frame rate you worked in in fusion as well? Is I possible the matte you created is 23.98 and resolve is bring it back in at a different frame rate?

(you sure do have a lot of issues with mattes :))

Glenn

[Michael Mccune]

Glenn; I was hoping you would chime in. Yes, trouble with mattes.

And, yes, all the work, from source to final, is 29.976.

You asked about my Fusion frame rate setting. So let’s start with my confusion over setting the Fusion frame rate:

Just for fun, try a search for, “29.976” in the Fusion User Manual or the Fusion Tool Manual (try Ctl+F to bring up a local search box for the document). What do you find??? There are NO entries in either manual for the term, “29.97” or for, “29.976.”

First, we note that Fusion has two “frame format” setting locations within Preferences, under Global and Default Settings and under and Composition/General.

These frame format pages each have frame rate data entry fields but they are pre-populated only with whole number integer frame rates, such as, “24, 25, 26, 27, 28, 29, 30, 31,” etc. Again, no “29.976 option.

But it seems that it is possible manually to enter a fractional frame rate in these fields. But not really.

That is, the frame rate field entry is constrained to two decimal digits, e.g., “29.97.” We know the actual frame rate is, ‘29.976.” So it is not possible, either by choosing an item in the drop-down list or by entering, “29.976” in this field.

So how is one supposed to understand this frame rate setting business in Fusion???? Seriously, what is the logic???

FWIW, the frame rate–so says the documentation–is determined by the frame format which is resolution independent. Don’t quite follow the logic, however.

Or, try a search for, “frame rate:” there is ONE entry in the Tool Reference but it only relates to stretching duration. In the User Manual it says, “Since Fusion is
resolution independent, comps do not ask you to define a resolution or frame rate. Those settings are determined in the Globals [sic] Frame Format preferences,” (from page 25). Don’t understand how resolution–to me that means the total number of pixels, horizontal x vertical, in some HxV ratio that is the format— can yield a rate. That is, a given format, say, 1920×1080, can be recorded at widely variable frame rates.

So how to they get there, a derived frame rate???

(Somewhere in this mix is also the question that the tiff file format does not have, I understand, ANY integral information about frame rate, as might be embedded in other codecs and file formats.)

If you find you have any helpful corrections or thoughts on this, Glenn, glad to hear them!

Thanks, Mike

[Glenn Sakatch]

Just to clarify, 23.98 is actually 23.976. I’ve never heard of 29.97 referred to as anything other than 29.97…(maybe as 30), but i wouldn’t enter the number as 29.976…I doubt if that would cause the problem you are describing, but i would start there.

Try entering that in fusion. If i get some time i’ll try a couple of tests tomorrow. To be honest, i very rarely work in 29.97 anymore, so i’m not sure if i’ve ever output it from fusion, but i have definately done what you are trying in 23.976 with success.

Glenn

[Michael Mccune]

Thanks, Glenn; you are right I believe about the number: 29.97 vs. 29.976.

BUT THE SOLUTION TO THE MYSTERY OF THE EXTERNAL MATTE FRAME OFFSET IS AT THE END OF THIS POST!

There are many online references to 29.976 but there is no derivation for that which I could find in a brief search today. So I agree and lets stick with 29.97.

As you must know, the 29.97 number comes from 30/1.001, which harks back to the first color TV days and their need to shift the frequency harmonics slightly. I understand that to reduce all the phasing from the color subcarrier, etc., they had to calculate out several orders of harmonics. Amazing. And they did all the math without computers.

Anyway, here is the actual solution, to the external matte offset problem, gleaned from this tutorial, https://youtu.be/zcUtbdT5Uxo, which mentions that imported external mattes line up with the start of the original clip, presumably the source time code.

And, indeed, my test clip had been shortened at the head by about 37 frames.

So, if one exports a portion of a clip starting at some point into the clip, not the start of the clip, and then the Fusion matte made from that portion is imported back into Resolve as an external matte it will not line up, as expected, with the start of the exported portion of the entire clip. Rather the external matte will line up with the start of the entire clip prior to export.

Why??? Dunno. Something that could be clarified in a later version of Resolve, sez I.

But how to fix it??? ANSWER: The external matte key tab includes an offset option. This critter is difficult to manage due to very high sensitivity: slight mouse movements can translate to relatively huge frame increments or decrements. And there is no nudge keyboard option that I know of.

With some fiddling with this control, the -37 frames adjustment did offset the matte to match the original video.

Funny but I tried this option before but gave up, supposing I didn’t understand how to use it as it would jump wildly in the frame count even with tiny mouse movements. And of course I needed only about 37 frames. (Actually, I wonder if the huge offset range results from scaling the long length of the entire original clip: not hard to jump to an offset with hundreds of thousands of frames. But this behavior makes small changes of a few frames tricky and actually difficult.

So I guess Resolve might include this as a feature request and refine this option to provide some sort of scaling and nudge capability.

Thanks again, for the commiseration, Glenn. Mike

[Misha Mazor]

Wow thank you. External mattes not syncing for me. Your offset solution worked.

[Luka Niemela]

Hey, i ran into the same issue and your post was really helpful, however when you explained that you can offset the matte in fusion, i just couldnt find this option. After a bit of trying out different things, i think i found an even quicker workaround, since the matte and the original clip perfectly aligned on the timeline and only were off in fusion and the color tab due to the original clip being trimmed at the beginning, when i selected both the original clip and the alpha matte aligned perfectly on my timeline and made a fusion clip out of them, the timing was already matched up and all i had to do was reconnect the matte clip as alpha for the original (+delete all the merge and background nodes resolve added when the fusion clip was created). No fiddling around with the Offset option as you mentioned