Virtual choir videos

electricfuse1 Posts: 18 Just Starting Out*

Anyone know any tips for large scale virtual choir videos? The type of video that requires 30+ videos on the screen at the same time. I think that I need to do something with resolution and downscaling it to make it more managable. I don't really have much knowledge on compression and how 30+ videos on one screen is gonna do. Will downscaling the resolution help speed up performance?


  • Triem23
    Triem23 Posts: 20,403 Power User
    edited June 2021

    Yes, you're on the right track.

    I don't know the final resolution for your project, so I'll assume 3840x2160 UHD (4k). All values will cut in half of you're working at 1080p

    So... 30 layers of 4k video is going to slow down any system. Even 30 layers of 1080p video! Before import to Hitfilm you're certainly going to want to downsample your video. You can do this with Hitfilm but you're better off using third party software instead. Handbrake is free, and will give you good quality video. There are even some tested, optimized Handbrake settings for good Hitfilm performance. This video has a section on Handbrake at 23:43. The values keyed into that one field and checkboxes shown are the optimized values. You'll be changing the resolution to something smaller.

    There are other, more general Handbrake tutorials on YouTube. Note Handbrake can batch render, so you can set up all your panels then start all the transcodes in one shot.

    Before transcoding I'd figure out how I'd lay out the 30 panels. The aspect ratio of a 1080p or 4k project is 16 horizontal units to 9 vertical units (16:9). Most webcams will be 16:9 as well, although some might be 4:3.

    Even grids would give you 9 (3x3), 16 (4x4) 25 (5x5) or 36 (6x6) panels. For 30 panels you're either doing a 6x5 or 5x6 grid, but this would change the aspect ration of each panel, so you'd have to crop everything to fit. Instead, consider a 6x6 grid. The bottom row then becomes a space for a "lower third" (a lower third is like the info bars at the bottom of a news broadcast), where you can show the name of your choir and your current song, or anything else you can think of.

    Cool, so lets assume we're doing a 6x6 grid!

    3840/6=640. 2160/6=360.

    So, for a 6x6 grid at 4k res each video should be down sampled to 640x360. If you're doing a 1080p video that's 320x180.

    Assuming the original camera streams are 1920x1080 resizing to 640x360 removes 88% of the pixel data. That'll be a lot easier to work with! (Resizing 1920x1080 to 320x180 removes 97% of the data!) This is where you're going to get a massive speed boost in Hitfilm from using Handbrake to downsample.

    Cool. Once you've shrunk your videos, what's the best way to arrange them? Well, you have two options. If you're in Express one of them is an add-on. Good thing there's a sale this week!

    The add-on option is "Split Screen Masking." This does exactly what you want to do - insert grids of panels. Drag all your videos into a Composite Shot. You'll be able to add Split Screen to a Grade Layer above the videos, set a 6x6 grid, then you just link each panel to one of your video layers. It'll take a couple of minutes. Then you'd place a lower third above the grade layer doing the split screen.

    Split Screen Masking is part of the Edit: Starter pack, and, if you bought any tier on the Pay What you Will page when you downloaded Hitfilm, you already have it. In fact, even with the sale, the PWYW is a better value.

    Without split screen masking you're doing one of the two following methods.

    First, you'd be manually dragging all the panels into place, or doing the math to input correct values into the position property for each layer. Boring, and you'd have to do this each time. It'll take you half an hour.

    Second, you'd create thirty 640x360 "media holder" Comp Shots (one for each panel), and add a video to each media holder. Drag each media holder into the main Comp and move into position. This will take an hour. The advantage here is, to reuse this layout you'd just change the video clip in each media holder and it'll automatically be in the proper location in the main comp.

    If you want all your panels at the 16:9 aspect ratio (6x6 grid, room for lower third at bottom), then use Split Screen Masking to save time.

    If you want a 5x6 or 6x5 grid (5x6=768x360. 6x5=640x432) to completely fill the screen with panels then do the method where you create the media holder Comps - you can then position your videos in the media holder Comps to get the crop.

    Same principles apply for other amounts of panels/videos.

    Any other questions? 😁

  • triforcefx
    triforcefx United StatesPosts: 1,647 Moderator
    edited June 2021

    Here’s a few tips that can hopefully help:

    One of your biggest issues will most likely be audio sync. You’re probably getting videos in multiple different frame rates (and almost certainly a lot of Variable Frame Rate video). You’ll need to transcode all your video to a common framerate (make sure it’s at a constant framerate and make it the same frame rate as your final video) to minimize audio sync issues in editing. Hopefully everyone in your choir sang at the same beats/min. If not, you’ll have a fun time manually adjusting the timing of the videos.

    When you transcode your video, you’ll also want to transcode to a common resolution. If you’re going to be showing 30+ people screen at once throughout the entire video, then you can probably get away with scaling the videos to 480p or even 360p. If there are any “featured” videos that will be bigger on screen (for instance, for a solo), use a higher resolution (such as 720p or 1080p)

    Transcoding to a common framerate and resolution should make your life a lot easier. After that, it’s a matter of designing your “grid”. The Split Screen Masking effect might be able to help a lot, though you’ll have to do it in pieces since an individual split screen effect only supports a handful of videos at once.

    Edit: @Triem23 has some great tips for the resolution and split screen stuff, but you’ll definitely want to take framerate into account as I mentioned in my comment as well!

  • Triem23
    Triem23 Posts: 20,403 Power User

    To build on @triforcefx he's right. You might have videos of different frame rates and some being variable frame rate (VFR). VFR can cause all kinds of issues, so that's just another reason to transcode first.

    Good catch, triforce. I forgot to bring up those points above. I think, between us, we nailed the answer.

  • electricfuse1
    electricfuse1 Posts: 18 Just Starting Out*

    @Triem23 @triforcefx Thanks a lot guys. I think I know what to do now. Didn't realize that split screen masking existed lol. Previously I would just manually scale and drag the videos into position. Definitely gonna give that a try now.