Intro

Our goal at SOUL is to make college-level course sequences, such as undergraduate majors or minors, realistically learnable from free online resources. If a major has 10 classes, putting up 10 majors means putting up 100 classes. And putting up 100 classes usually means getting the lectures (and recitations) of 100 classes recorded. I used to think that this should be fairly easy, but it’s turned out to be non-trivial. Looking back, this was to be expected: logistics is hard.

MIT OpenCourseWare’s standard method to record a class would be to hire MIT Video Productions (MVP) to record the class.¹ MVP’s rate is something like $10,000-$20,000 per course (a standard full-semester lecture-based course at MIT may have ~24 1.5-hour lectures or ~36 1-hour lectures). If we want to scale, we need a different strategy to record classes.

A minimal setup

Consider this minimal setup:

• put someone’s smartphone on a stand (plenty of cheap phone stands you can buy on Amazon) somewhere in the classroom, pointed at the instructor
• start a recording on the phone at the beginning of class, and stop it at the end of class
• have the instructor start a zoom recording on their laptop at the start of class

In doing so:

• audio is recorded through the phone’s mic and the laptop’s mic
• the classroom projector screen, if used, is captured on the phone video and also through zoom via the laptop screen share
• the chalkboard/instructor is captured on the phone video

With this setup, neither the audio nor video is great, but they are sufficient to edit together a recording of the class that’s tolerable. Rather than have nothing, if I really wanted to learn something and couldn’t learn it anywhere else, I’d be happy to watch the video that results from this setup. In fact, smartphone cameras are so good these days, the recording would probably be much better than tolerable. If we were to use a good microphone, the recording would be good, even.

For example, here are screenshots of some 6.828 lecture recordings from the 2011 and 2014 iterations of the class, found on YouTube. The recordings appear to have been informally captured by students using their phones, tablets, or laptop webcams. Surprisingly, they managed to record most of the classes and uploaded nearly complete playlists of lectures in the course. The comments on YouTube are full of people expressing their gratitude for the materials and asking where they can find the handful of missing lectures.

When I talk to people about how to get classes recorded, many people propose this kind of minimal setup. “It’s so easy to do this, everyone has a smartphone these days, just put it on a stand and record.”

Why it’s hard to get classes recorded

There are two reasons it isn’t actually so easy:

1. It's just more complicated than you think to get something supposedly simple to work reliably across a distribution of scenarios.

2. You need someone to perform the setup, and we can't rely on the people we have available in the classroom to do it properly.

Expanding on 1:

• Placing the phone such that everything we’d like to be in view, is in view, takes some care. Ever given a stranger your phone to take a picture of you? Most of the time the picture turns out bad.²
• If the ideal phone position isn’t in the first row of seats, how do you make sure students don’t sit in front of the phone?
• What if a student knocks the phone over?
• How do you make sure the phone is sufficiently charged to stay on the whole time?
• How do you make sure the phone camera refocuses properly if it ever gets out of focus? It might change focus when students walk across the classroom.
• How do you make sure the phone camera exposes properly if it every changes its exposure? It might change exposure when the projector screen toggles on/off.
• Who in the classroom will volunteer their phone?
• Does their phone have enough storage space for the recording? If the recording is done at max resolution, it’ll be big: a 1080p video at 30fps for 1.5 hours is ~11.7GB.
• How do you get the recording off their phone? Do you ask them to submit it somewhere?
• …

Expanding on 2:

We can’t be in every classroom, so we rely on one or more of the instructors, TAs, and/or students to do the setup. However, their focus is elsewhere. Their primary motivation to be in the classroom is, rightly, not to do a setup task. Even if we pay them, keep the setup short, provide clear instructions, and give them a walkthrough the first few times, finding and training someone to do the setup correctly and maintain that standard consistently is challenging in practice.

More generally, there are three reasons why it’s hard to get classes recorded:

1. Things are more complicated than you think.
2. People can be unreliable.
3. Technology can be unreliable.

I’ll end with a concrete example of difficulties we faced in recording a particular class this fall semester that illustrates each of (1), (2), and (3).

A concrete example

A course we wanted to record lectures for this fall was in one of IS&T’s autocapture rooms. Knowing that their provided microphone often has problems (and it’s so unfortunate when we lose audio for a lecture, because it’s a lot to ask the instructor to give the lecture again), I decided on the following strategy to reliably record the lectures:

• Record via IS&T’s autocapture system (video of classroom + audio)
• Record via zoom on the instructor’s laptop (backup audio, backup capture of projector screen via laptop screen share)
• Record via portable audio recorder (Sony ICD-PX470) (backup audio)

Here are the steps I provided to the instructors, which I also taped onto the table where they would place their laptops. These instructions remained on the table throughout the semester. The steps take 30 seconds at the start of class (joining a zoom meeting, starting the audio recorder, putting on the lapel mic), and 30 seconds at the end of class (ending a zoom meeting, stopping the audio recorder, taking off the lapel mic). I went to class the first few times to help walk them through the steps.

Despite instructions that were easy to follow, reminders about what to do, and a very patient and cooperative teaching staff:

• In 15 out of 23 lectures, audio was missing in the IS&T recording (cause unknown).
• In 2 out of 23 lectures, the portable audio recorder wasn’t started.
• In 23 out of 23 lectures, the zoom microphone was not umuted.

We ended the semester with 2 lectures that did not have audio from any of our three audio sources. Unfortunately, we won’t be able to rerecord those lectures until next fall.

Should I consider even more sources of backup audio next time?³

Conclusion

Recording classes should be very easy, but it can be hard to achieve at scale.

Teaching staff already have a lot to worry about. Is it reasonable to expect them to be able to help with recording setup? Next time, should I also recruit some students in the class to help? My experience hiring students to do lecture scribing work tells me otherwise – they can also be unreliable.

My main takeaway from working to get classes recorded over the past few years is that, if you want to get something done reliably, you need someone on the ground who’s primary responsibility it is to get that thing done. Maybe we can’t avoid hiring people specifically to handle recording logistics, but I’d prefer not to – it seems like a waste of resources when the recording setup, especially in autocapture rooms, requires following just a handful of steps. When instructors put in a little bit more than $\epsilon$ effort into recording logistics, really nice recordings can result, such as the recordings from the entirely student-taught Introduction to Data-Centric AI, which has turned out to be very popular online.

MIT instructors often handle extensive setup tasks on their own, especially for lab classes. While open education is already more present in MIT’s culture and values compared to other universities, it is still limited in scope. If we made it an even more central part of the culture, perhaps we could make recording setup a default responsibility of teaching staff, allowing us to cost-effectively scale to recording hundreds of classes.