This post is a bit different from the previous ones -- it simply shows what I've been doing for some time to create supporting videos for my students.
I record my voice using Audacity, and I use KDENLive to make the videos. I make slides using google docs.
Once you've got used to this you can make a bunch of short videos (aim at 6 minutes or so) in a single day.
Here's my work flow:
1. Create a script for the audio.
I basically write down everything I'm going to say before I've made my slides. I then make the slides to match the script.
I use gedit to write my script.
2. Create the slides to match the audio
I use google slides:
I export each slide as a png:
3. Record the audio in audacity
Use a good microphone! I'm using a Blue Yeti, which is great.
NOTE: each audio file should correspond to a single slide, or part of a slide. Not the other way around. It makes step 4 easier, and helps if you need to redo the audio for a section.
Export the audio in a suitable format (e.g. flac)
4. Fire up KDENLive
Import your clips.
Add your audio to the Audio channel
Then add the png files to the video channel. Stretch the duration of each image file to match the duration of the audio.
I've looked at a few different solutions, but I've basically settled on recording video and audio separately. The downside of this is that I won't stream. The advantage is that I can do post-processing to add clearer pictures of slides etc.
When it comes to audio I've explored a range of solutions:
* Bluetooth headset -- this would've allowed me to stream, but the sound quality is just too poor with bluetooth (I tried Blueparrot B350-XT). For an example of how bad it can be, check out this corporate(!) video:
Advantage: wireless, can stream, only covers one ear
Disadvantage: Sound quality
* 2.4 GHz Wireless headset -- I tested Logitech G930. The sound quality is OK, but it covers both ears, and makes it hard/ uncomfortable to deal with a live audience.
Advantage: sound quality, wireless, can stream
Disadvantage: shuts out the live audience
* 'Normal' microphones -- I have a number of microphones, including Blue Yeti. Many of them are wired (USB), and none of them will work in capturing a moving (i.e. mobile) lecturer.
Advantage: superior audio -- when very close, streaming
Disadvantage: poor audio unless you're right in front of the mic
* Mobile phone lavalier mic -- See here for how to do that: http://verahill.blogspot.com/2020/07/658-teaching-during-pandemic-part-1-how.html.
Advantage: great sound, mobile, can potentially stream
Disadvantage: drains phone battery, can be tricky to set up LAN, if using receiving device (laptop) as hotspot you may not be able to connect to the internet (i.e. can't stream)
My chosen solution:
* Using a portable audio recorder (e.g. dictaphone) -- I've got a Zoom H1n, and a lavalier microphone. I love this microphone. It's lightweight, portable, not too expensive, and the internal XY microphone is great (to my ears). The amplifier for external mics is a bit weak, but it works for my purposes, especially if you post-process in Audacity. But that leaves you having to sync your video and your audio in post. I've already showed you how easy it is to do that here: http://verahill.blogspot.com/2020/07/659-teaching-during-pandemic-part-2.html
Note that you need to invest in a decent lavalier microphone as well. Also note that most these days seem to come with a 3.5 mm TRRS connector (good for mobile phones), and the Zoom needs 3.5 mm TRS (the old standard). Many of the cheap/affordable lavalier mics that you find on e.g. Amazon come with TRS/TRRS adapters, so it's not much of an issue.
Advantage: potentially great sound, great battery life
Disadvantage: you can't stream live, needs a lavalier microphone
So there we are -- I'll set up a single webcam to record video directly to my laptop. I'll capture the sound using it as well, but mostly to help me sync the audio later. I'll record my voice using a dictaphone and a lavalier microphone, post-process the sound in Audacity, then import video and audio in KDENLive, where I'll sync everything. I can then add pictures of my slides as well, and don't have to worry about the image quality during recording.
This is a very short post. What if you need to set up two (web)cameras that capture from e.g. different whiteboards?
I had a look at OBS studio, and it's not stable for me. Sometimes I get a cam image, and sometimes I don't. I also had issues with getting two cameras to work. I also looked at webcamoid and cheese. The frame rates were too bad.
What does work for me is guvcview. This is available in the debian repos.
I'll also show you how to sync the sound using KDENLive
1. Install guvcview
sudo apt-get install guvcview
2. Start guvcview.
Then go to video controls.
Select a new Device, then select New
Now you've got both feeds showing:
Then you can simply record:
I won't go into how to switch back and forth between angles in KDENLive. I'll just show you how to sync the videos using the audio:
Import both clips into KDENLive and put them in separate channels. Right-click on one of the tracks, and make it the audio reference:
Align the other clip:
They are now aligned:
Note that you could have done this with a pure audio track as well (we'll get to that in the next post).
You can then start cutting away bits you don't want using the x/scissors:
