Choppy playback on large files

Very large or high-resolution videos can stutter when you preview them, because your Mac is working hard to decode the full file on the fly. The fix is to build a preview proxy — a smaller, lighter version Brolla uses just for smooth previewing.

When Brolla notices a heavy file, it offers to Build preview first. Let it do this and playback becomes smooth. Your original file is never altered, and any export always uses that original at full quality.

Codecs that can’t be previewed here

Some formats, like ProRes, may show a message that they can’t be previewed here. That’s just the format being more than the built-in player handles directly. The answer is the same idea: choose to Generate a lightweight H.264 preview.

As the message reminds you, the original is untouched — the H.264 version exists only so you can watch and trim comfortably, while exports still draw from your pristine source.

A black or frozen preview

If a preview shows up black or frozen, it usually means the proxy hasn’t been built yet for that file. Look for the Build preview or Generate a lightweight H.264 preview option and let it finish, then try playing again. If it still won’t play after a fresh preview, the source file itself may be incomplete or corrupted — try opening it in another player to confirm.

Through all of this, remember: building previews never changes your originals, and your exports always come from the full-quality source file.