20. 04. 2021 Charles Callaway Documentation

Making Your Own Video Tutorials, Part 4: Editing and Compositing

In my previous blog post we looked at how to use a green screen to add an extra touch to the tutorial videos you upload to YouTube, particularly focusing on the ambient space for filming, the lighting (both the screen itself and the subject), and the necessary audio and video equipment.

The goal of using a green screen in tutorial videos is usually to add a video overlay of yourself explaining something on top of an existing video or slide that contains what’s being explained. The process of overlaying some elements on top of others to produce a video is called compositing. This is typically one aspect of video post-production, which consists of all the stages between filming and distribution.

Because tutorial videos will usually be produced indoors in a highly controlled setting with no motion or actors, we shouldn’t kid ourselves that we’re on our way to becoming professional video editors. But there’s still a lot we can do to improve the videos we make. After all, these days even a third grader can make a movie.

As developers, we also have one advantage over professional video editors: we’re already the domain experts: we know our product thoroughly, the industry we work in, and the outlook of the people in that industry. We know what they’ll find condescending, what’s inspiring, what needs to be said and needs to be left out, and what they see as the state of the art.

What’s Involved in Post-Production?

There are three major tasks you’ll need to carry out once you’re satisfied with filming, collectively called post-production:

Video editing: Altering the original video itself
Compositing: Adding new visuals (video or graphics) on top of a background video
Audio editing: Altering the existing video or adding new audio

Of course in the modern era, we’ll do all the above digitally. So whichever software tools you choose (see the next section), make sure that they can handle all the operations listed here.

The two principle tasks in the video editing phase are preparation, which changes the visual characteristics of the filmed segments, and the timeline, which determines what gets shown and in what order.

Video preparation phase

Cropping and resizing – Especially when creating an inset (PiP) video, you may want to remove anything outside a particular bounding square so that it doesn’t appear when composited, and resize and reposition the newly cropped video within the available screen space.
Chroma key creation – Often used for background removal for inset video, this is part of the green screen video process.
Color correction – Correcting for any deficiencies in lighting during the filming phase (or in movie filming, change the colors implied by the lighting to modify the mood).

Video timeline phase

Cutting for removal – Removing unwanted sections of video that are either before or after the desired video (video you intend to include in the final result).
Cutting for splicing – Dividing a section of desired video into two parts, so that you can later reorder them or insert a different video segment between them.
Ordering – Choosing which video segment to place first, which to place second, and so on. Occasionally you may also want to copy a video segment to show it twice.
Changing the speed – While this is rare in movie-style filming, when creating screencasts you will often find that there are “slow movements” which can’t be cleanly cut, for instance when the mouse is moving across the screen.

Compositing

Compositing is putting graphical objects, usually computer generated, on top of a background, which is usually a video. As with the computer desktop metaphor, each graphical object has a depth value, so that foreground objects are overlaid on top of objects further in the background.

Static graphics – The addition of visual graphics and text like you might find in PowerPoint and similar applications.
Animated graphics – Like static graphics, but whose shape, size and motion paths are interpolated over time, often according to a library of preset animations.
Picture-in-picture – For our purposes, this is a processed video (e.g., resized and with the chroma key replaced) that is overlaid on top of a background video.

Audio Editing

The audio for a video can be processed in a number of different ways:

Dialogue editing can be used to change speech quality, replace it completely, or dub in a different language. For tutorial videos, it’s much more likely to be used for volume adjustment, since it’s easier to just re-record if something goes wrong, and there is very little interference since it’s from an indoor environment without other actors.
Adding music (whether foreground or background) and sound effects. Most people are able to competently film or create a screencast, but not write, perform and record music. Be sure you use music with no royalties or copyright restrictions. There are lots of free online sources, including YouTube itself.
Editing: Given an audio file, you will probably want to fade it in and out, and adjust the volume. Most video editors will have limited capabilities built in, otherwise you can import files from a more sophisticated audio editor.

Post-production tools

The software tools you use (whether a strict video editor, or one with features specifically for tutorials) needs to address the general editing requirements above. I’ve also noted some helpful additional features and restrictions that are technical in nature:

If your green screen video wasn’t good and you can’t set up another take, having a video editor that supports multiple chroma keys can fix some of the problems. (In general of course, it’s easier to get it right during filming than fixing it later, so make a note to plan better next time!) As I noted in my last blog post, these problems are often due to (1) excessive shadows on the green screen, and (2) excessive spill of green light on the shoulders of the subject. More advanced chroma keying will let you key off of multiple colors (shades of green) or allow you to select a color space (think RGB, CMYK, YUV, HSV, etc.)
Beware of compressing video files. It can introduce pixellation, and change specific RGB values, rendering your green screen useless. If you’ve shot video at a resolution that’s too high, consider reducing the resolution either while shooting, or before importing it into your video editor.
Don’t fall into the trap of thinking that you can remove a green screen background, export the video file, and then import it into another program for editing. There are no truly transparent video file formats, transparency only exists within a single application that supports compositing. If you need to pass intermediate files, export the video with a processed chroma key background, so that it is already reduced to a single RGB color, which can be easily processed by the final video editor.
Why do you need to worry about multiple video editors? Most high quality video effects (VFX) software is set up to apply video effects non-linearly on timelines, they aren’t optimized for making tutorial videos. Meanwhile, most tutorial video applications don’t have a lot of specialized video effects (e.g. high quality chroma key and video cropping) and highly parameterizable animations for graphics. Your pipeline should first go through a VFX application, and final editing should be done in a tutorial application.

If you’d like some recommendations, I use the following applications, all of which are free with premium options, and without watermarks (features may be disabled, but the final videos are just plain videos):

Photoscape Editor for simple manipulation and resizing of static graphics, almost exclusively for screen captures, blurring of private data, and for cropping out extraneous detail.
VSDC Video Editor for video cropping, color adjustment (I hate seeing my face too orange), and green screen background removal. Since I transfer out the video for a picture-in-picture effect, I replace the green screen with a single RGB value which the next application can easily remove.
ActivePresenter 8 for compositing all the pieces on a single timeline, adding animations and graphics overlays for emphasis or clarity, and exporting the final video to YouTube.

Creating a Post-production Pipeline

Whichever set of applications you choose, you can save a lot of time in post-production by creating a concrete, ordered pipeline of the actions you need to perform. It will save you even more time if you’re planning to create a lengthy series of videos.

As with most artistic endeavors, you’ll want to use the iterative design paradigm: write down what works best so far, and then each time you find something slightly better, update your written pipeline.

As an example, here’s my current pipeline, after being updated for the use of green screen overlays:

Use a template project for ActivePresenter. Whenever it’s time for a new project, copy that project file and rename it in its own directory. Keep it updated.
Add the written tutorial content as preliminary slides in that project.
Plan the overall organization of the tutorial, what actions to include in the recorded screencast, and what video segments will be needed (this corresponds to a storyboard, but without the hard hand-drawing work).
Record the screencasts of the target application in ActivePresenter (the slides and the screencasts represent all of my full-size backgrounds that other graphics elements will be composited on top of).
Edit the screencasts by cutting and speeding up the slow parts – when done, we’ll know about how long the entire video will take, plus or minus 10%.
Write out the full text of the narration that will fit within that time limit.
More finely edit the screencasts, fix any privacy issues like names or IP addresses, and plan when graphics will be composited to add emphasis and improve clarity.
Record draft audio to go with the video, refining the text so that spoken references to visuals occur at the same time as it is seen in the screencast.
Record the green screen video with teleprompter in a capture program, and use VSDC to crop the video so all the background is green, remove the chroma key, and substituting the same color as we use in the background of the slides so that it will look transparent when composited.
Back in ActivePresenter, composite the green screen, make final video edits, and then record the final audio in a single linear session with a high quality microphone.
Export the final video and back up all video project files, application project files, scripts and other resources, using templated, sequentially numbered names.

Conclusion

So now you probably know more than you wanted to know about post-production, unless you’ve just been tasked with creating a tutorial video from scratch by yourself. On the other hand, maybe you’ve already made a few videos, and you find yourself dreading the post-production phase because it seems like too much work.

Once you thoroughly understand all of the steps involved and get comfortable with a fixed pipeline that works for you, I think you’ll begin to realize that most of what slows down post-production is actually unresolved problems stemming from the video shooting phase.

Next time we’ll look at YouTube as a publishing destination, see you then.