Uploaded October 2009 | Updated September 2026, 33 minutes ago
The laser's back and this time I'm finally getting around to trying out some real-time effects using JACK. This is a simple circular oscilloscope (look ma, no retrace!) spinning at some multiple of Middle C frequency, which works particularly well for music. I found that chiptunes, due to the simplicity of the waveform, show up in very interesting ways. Keep in mind that this is a crappy 30fps digicam capture; it looks a lot better in real life. The sync is also a wee bit off here, in real life it's perfectly synced by design (audio and laser outputs are synchronous).
The song is Visitors From Dreams by Dma-Sc :)
Although not shown, blanking and brightness modulation also works, though the laser has trouble achieving full power unless it's on 100% of the time. Here (fully on), it's probably putting out 40-50mW or so - I measured 60mW when I got it but I run it a bit lower here for safety.
Note that the room lights were on and the window was fully open when I took this video: I had to turn down the exposure on the camera to reduce the artifacts caused when the image is acquired from the camera sensor. You can still see them somewhat, particularly right at the very beginning, above and below the circle.
Random tidbit: the blink at the beginning was caused by a JACK xrun that occurred as the music started. The safety controller on board the laser kicks in and shuts down the laser at most 0.5ms after it senses a failure of the software, and keeps it that way until it gets a stable signal for a few hundred ms. I do this by dedicating one soundcard channel to a 1Khz pilot signal - when it disappears, even for one cycle, the safety controller powers down the laser. It also does power supply monitoring and short circuits the laser as soon as it senses the main PSU output falling, which hopefully should eliminate any dangerous (for the laser) transients.
The laser's back and this time I'm finally getting around to trying out some real-time effects using JACK. This is a simple circular oscilloscope (look ma, no retrace!) spinning at some multiple of Middle C frequency, which works particularly well for music. I found that chiptunes, due to the simplicity of the waveform, show up in very interesting ways. Keep in mind that this is a crappy 30fps digicam capture; it looks a lot better in real life. The sync is also a wee bit off here, in real life it's perfectly synced by design (audio and laser outputs are synchronous).
The song is Visitors From Dreams by Dma-Sc :)
Although not shown, blanking and brightness modulation also works, though the laser has trouble achieving full power unless it's on 100% of the time. Here (fully on), it's probably putting out 40-50mW or so - I measured 60mW when I got it but I run it a bit lower here for safety.
Note that the room lights were on and the window was fully open when I took this video: I had to turn down the exposure on the camera to reduce the artifacts caused when the image is acquired from the camera sensor. You can still see them somewhat, particularly right at the very beginning, above and below the circle.
Random tidbit: the blink at the beginning was caused by a JACK xrun that occurred as the music started. The safety controller on board the laser kicks in and shuts down the laser at most 0.5ms after it senses a failure of the software, and keeps it that way until it gets a stable signal for a few hundred ms. I do this by dedicating one soundcard channel to a 1Khz pilot signal - when it disappears, even for one cycle, the safety controller powers down the laser. It also does power supply monitoring and short circuits the laser as soon as it senses the main PSU output falling, which hopefully should eliminate any dangerous (for the laser) transients.
![Work stream: Writing a hypervisor Pt.11 [2021-05-24]](https://i.ytimg.com/vi/v56QkqW7p_4/mqdefault.jpg "Work stream: Writing a hypervisor Pt.11 [2021-05-24]
Mmiotrace hypervisor, maybe?
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In these streams I show how I work. I may or may not talk, and I may or may not read the chat. If you need to catch my attention, its probably best to ping me on IRC, check out asahilinux.org for details!
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I do not broadcast background music, for copyright reasons and because my music tastes may not match yours. I highly recommend bringing along your own music!")
![Work stream: AIC and exceptions [2021-01-16]](https://i.ytimg.com/vi/vF-ywrkd5eE/mqdefault.jpg "Work stream: AIC and exceptions [2021-01-16]
More mini scaffolding and investigation into Apple-specific peripherals
Website: https://asahilinux.org
Patreon: https://patreon.com/marcan
GitHub Sponsors: https://github.com/sponsors/marcan
In these streams I show how I work. I may or may not talk, and I may or may not read the chat. If you need to catch my attention, its probably best to ping me on IRC, check out asahilinux.org for details!
There is currently no set schedule for these streams, so subscribe and click the bell if you want to be notified when they happen.
I do not broadcast background music, for copyright reasons and because my music tastes may not match yours. I highly recommend bringing along your own music!")
![Bringing up Asahi Linux on the M1 Pro [2021-11-01]](https://i.ytimg.com/vi/wBQYQh-e0Ow/mqdefault.jpg "Bringing up Asahi Linux on the M1 Pro [2021-11-01]
The M1 Pro is on the way. Lets make Asahi Linux run on it!
Website: https://asahilinux.org
Patreon: https://patreon.com/marcan
GitHub Sponsors: https://github.com/sponsors/marcan
In these streams I show how I work. I may or may not talk, and I may or may not read the chat. If you need to catch my attention, its probably best to ping me on IRC, check out asahilinux.org for details!
There is currently no set schedule for these streams, so subscribe and click the bell if you want to be notified when they happen.
I do not broadcast background music, for copyright reasons and because my music tastes may not match yours. I highly recommend bringing along your own music!")
![Work stream: Linux upstreaming feedback [2021-02-11]](https://i.ytimg.com/vi/x8f9-E_eP4M/mqdefault.jpg "Work stream: Linux upstreaming feedback [2021-02-11]
On the road to v2
Website: https://asahilinux.org
Patreon: https://patreon.com/marcan
GitHub Sponsors: https://github.com/sponsors/marcan
In these streams I show how I work. I may or may not talk, and I may or may not read the chat. If you need to catch my attention, its probably best to ping me on IRC, check out asahilinux.org for details!
There is currently no set schedule for these streams, so subscribe and click the bell if you want to be notified when they happen.
I do not broadcast background music, for copyright reasons and because my music tastes may not match yours. I highly recommend bringing along your own music!")
