Apple Final Cut Pro X Forum
Playing hundreds of clips at once in FCPX
Playing hundreds of clips at once in FCPX
by Cat Heller on Oct 5, 2018 at 6:32:04 pm


I'm trying to make a video where 144 small clips play at once with no special effects or text. I bring each MP4 clip (mostly shot on smartphones) in and resize them to 11% and desaturate them. I then place them side by side. All was going well until I got to around the 100th and when I try to edit the clip or move it around, the viewer goes blank and I cant see where I'm placing the clips next to each other. When I delete about 20 or so clips, it seems to restore itself and work again. I'm new to FCP, so I'm wondering if there's a better way I could have built the timeline? Or is there a better workflow that would make FCPX work better?

I would really appreciate any help or point in the right direction.

Thanks so much,

Re: Playing hundreds of clips at once in FCPX
by Jeff Kirkland on Oct 5, 2018 at 9:34:32 pm

What Mac are you editing on? From your description, just wondering if you’re hitting the limit of your computer’s GPU RAM or maybe some sort of throughput issue because of the number of clips.

My thought would be to either batch resize the videos before bringing them in to FCPX or to render the first 80 or so clips, then bring that new clip back in and add the rest. You might also try grouping some in a background clip and letting that background render. I think FCPX will keep using that background rendered version as a single clip until you make a change to the contents of the compound clip, which might ease the load a little.

I’ve never had it happen to me so just a few stabs in the dark...

Jeff Kirkland | Video Producer & Cinematographer
Hobart, Tasmania | Twitter: @jeffkirkland

Re: Playing hundreds of clips at once in FCPX
by Joe Marler on Oct 6, 2018 at 12:17:13 pm

[Cat Heller] "trying to make a video where 144 small clips play at once...mostly shot on smartphones...resize them to 11% and desaturate them.."

The below article discussed doing this for 64 concurrent videos on a top spec 2013 Mac Pro. You are doing over twice that.

"Building a 64 layer chessboard project in Final Cut Pro X":

If I understand correctly, you are playing 144 concurrent video streams simultaneously. Is that right? If so that is extremely challenging -- on any NLE or any hardware. This would especially be so for H264 which is likely what the smart phones use. Some may even be HEVC which is much more compute-intensive than H264. If any of those are 4k it's even harder.

It might be best to transcode everything to 1080p ProRes or create proxies for everything (proxies are 1/2 the linear and 1/4 the area resolution), so proxy of 4k is 1080p and proxy of 1080p is 960x540. This is usually adequate resolution for editing and will greatly increase performance.

If you are already using proxies, the only solution might be get a faster machine. You will also likely need a high bandwidth I/O system. Even if all your content is 1080p/30 H264 at the iPhone spec of 130 MB/min, this still equates to 2.2 MB/sec * 144 or 317 MB/sec, with nothing left over for anything else such as cache, library I/O, etc.

Or -- if your video tiles are always small and never grow to a larger size, you could possibly use Compressor or Handbrake to transcode those before ingest to a lower resolution, such as 480x270 or smaller. That would decrease the CPU and I/O burden.

Re: Playing hundreds of clips at once in FCPX
by Brett Sherman on Oct 6, 2018 at 3:13:49 pm

I had this exact scenario. I managed to muddle through it. I don't think transcoding is going to get you very far. Because the cost of reducing decompression demands is increasing the disk throughput demand. Both are issues in this scenario. Resizing clips would help, but it would take a long, long time. And you'd be resizing sections of clips that you aren't using.

Here's what I did Compound groups of clips together. So line up 20 or 30 shots in your timeline. Select and right-click "Create Compound Clip." Open the compound clip you just created. Export a Quicktime Movie (ProRes). Drag that resulting file to the top of your Compound. Then disable every other clip in the compound. Repeat with the remaining clips. This way your main timeline it is only playing the one clip.

If you want to re-render with full resolution. Disable the outputted ProRes files at the top of the Compound. And enable the individual files.

Re: Playing hundreds of clips at once in FCPX
by Steve Connor on Oct 6, 2018 at 4:29:15 pm

I would certainly export the video in sections of 20-30 clips and then build the finished version out of them. No way I would expect any NLE to play all those highly compressed clips simultaneously

Re: Playing hundreds of clips at once in FCPX
by Brett Sherman on Oct 7, 2018 at 1:06:35 pm

I forgot to mention that you'll have to crop or mask the resulting ProRes file. Otherwise it's going to show black in areas where you don't have clips. So it's best to work in blocks.