What's the best way to hide burned (hard-coded) subtitles using FCP tracker or mask?

Thank you, Luis and terryb, I did have some success and to demonstrate the issues, I'm attaching an example. It's from an old film clip has hard-coded (burned) in subtitles (in Italian) and I've embedded new (soft-coded) subtitles in English on top.

I used the technique terryb mentioned and stumbled upon what Luis mentioned about the blend mode (although I used "difference" mode). The good news is that the magnetic mask can be made to work well enough that new black areas cover the old burned subtitles and go away when there are no subtitles. But the bad news is that it gets confused when there are high contrast elements nearby.

Specifically, you can see that the magnetic mask fails when background trees, shirts, countertops, etc... are near the subtitle region, no doubt because they have high contrast regions similar to the black and white of the subtitles. Nevertheless, you can see that it's relatively easy to read the new embedded subtitles.

I had the most success when I made the magnetic mask be somewhat bigger than the black boxes surrounding the burned subtitles (by an amount about equal to the height of those boxes). Still, the magnetic mask tended to "hug" the subtitles (that's what is normally should do in normal use-cases). I also found it was best to use 100.0 for the "feather" setting of the magnetic mask. Of course, one can go back and touch up the magnetic mask areas but that can get tedious.

So, my conclusion is, yes, this can be done, but at least so far, the result in my hands is a bit distracting. Whether it's better than a constant black rectangle in that area is questionable. The whole problem, of course, is that the magnetic mask is designed for something much more sophisticated than this simpler task, and we're fighting against that sophistication. Of course, if Apple folks wanted to make a tool to do this it would be easy by comparison.

Helped me learn some things FCP can do.

[Edited by Moderator]

I'm posting a video using "blurArea" from @fox_m corresponding to the one I posted in the original post.

In the earlier video, I tried to hide the burned-in subtitles using FCP's magnetic mask but since the result was too distracting I opted instead for simple black bars to cover the burned-in subtitles (not shown) -- a pretty ugly solution.

I feel that the blurArea result is much better, although one does have to experiment to get the best effect. My approach was to find a blur area that didn't look too bad when no subtitles were present and just apply it to everything without worrying about turning the effect off and on repeatedly--even though that's a great feature, it can be a lot of work. Indeed, that's the one advantage of the FCP magnetic mask effect: it is smart enough to turn off and on as needed. But, as noted previously, it's just not suited to this task

@claude_210 thank you for your response. If I understand correctly a whole band at the bottom of the video will be affected rather than just the area with the text. I was really looking for something that affected just the text itself and that's why I mentioned methods involving the tracking and magnetic mask features of FCP. You see, I'm kicking the tires of FCP to decide whether I want to make the $300 purchase and so I'm as interested or more in seeing what FCP can do as I am solving this particular problem. I'm very impressed by these incredible tracking features of FCP and, as I mentioned, I've actually done it with partial success already despite my lack of skill.

@terryb thank you for your response. I'm referring to the type of subtitles one finds in a foreign language film, where the subtitles are always located in one place at the bottom middle while the rest of the video may do anything.

In fact, I believe this might be key to the solution: restricting the magnetic mask to just the area where the subtitles are by applying a second shape mask. I don't yet know how to apply these 2 masks like this, but the reason I think it will work is because when I first crop my video to show only the subtitle area, I'm able to get the magnetic mask to grab just the subtitles -- it still gets a little lost sometimes, but mostly is working.

So, if anyone can provide quality instructions for restricting the magnetic mask to a small portion of the screen like this, I'd be grateful.

@terryb I did what you suggested and was able to apply the magnetic mask exactly as I want for the trimmed section in the above duplicate clip. That is, within that little rectangle it colors just the text which I want to make disappear -- I had to "train" the magnetic mask by moving forward frame by frame at first and re-adding to it, but this was only for, say 5% of the clip or less, and after doing that it analyzed the rest of the clip on its own perfectly. So when I click the little silhouette figure in the magnetic mask tool control at right, the text becomes black as I play that clip, just as I want.

So how do I combine this with the inactivated clip below to see the whole clip with this effect? I tried clicking the lower clip and typing v but that didn't work

I don't know what you mean by "apply a negative 100% effect" so I was unable to test what you are suggesting. I thought that you were referring to the compositing options that appear in the upper right, but there are no less than 26 options in that menu. I tried quite a few of them, but none of them made the text begin to disappear around 50% like you described.

The technique that I felt gave the least distracting result was to make 2 black rectangles (for each subtitle line) sized at the minimum possible to hide all subtitles. Doesn't take advantage of FCP's intelligent features at all, and it means those two black rectangles are there even when there's no subtitles.

fox_m wrote:

I made an effect, tentatively called "Blur Area",

Please let me know when you've downloaded it — it's only available for about a day... maybe.

@fox_m Thanks for your response. I still have about a month on my FCP trial so I downloaded your "Blur Area" -- but didn't know how to installl it. I found this page but got stuck on the "Category" part -- the instructions say "(A lot of people miss this step…)" and I can see why. I see the following subfolders in the ...Movies>Motion Templates>Effects folder and have no idea in which of these to place the sc_blurArea folder

DesignStudio

mRotoAI Expansions

mFilmLook

mTracker 3D

mFlare 2

mTracker Surface

motionVFX Freebies

mRotoAI

@fox_m your linked article (broken video link; says it's private) was an interesting way to generate subtitles. Turns out FCP's ability to generate subtitles and magnetic mask were what attracted me to possibly purchasing and my posts in this thread were part of my testing. One of my interests is generating .srt files for language learning, but FCP only transcribes to English and lacks accuracy. The mCaption extension solves both these problems, but is expensive and also struggles with mixed languages. Then I found what I think is the source of (at least some of) these transcription tools: Whisper, which can be used for free.