Archive for the ‘Random’ Category

Testing MMSSTV with messed-up signals

Tuesday, October 31st, 2017

I applied a couple of strong vibratos to an SSTV signal (a picture encoded as one long sound) just to see what effect the unstable frequency would have when decoded using MMSSTV. Amazingly, it was still able to detect the signal and start decoding, but of course, it looks too scrambled to make out. I like how the artifacts look, though.

[Watch in HD]

I’m using Virtual Audio Cable to connect MMSSTV (encoder/decoder) with Audacity (which I used to apply the excessive vibratos), and Audio Repeater to “echo” the sound from the virtual cable to the speakers, so I can hear it live (and capture it in the video). Audio Repeater introduces about half a second of delay, though.

SSTV (slow-scan television) is a way of transmitting pictures over the air when you have very little bandwidth available (around 2.6 KHz, vs several MHz for ordinary analogue TV), sometimes used by amateur radio operators. It works by modulating the frequency of a sine wave according to the brightness of the pixels (per colour channel) row-by-row, so by applying a vibrato to the sound, the sound is pulled into and out of phase (but still stays in-phase on average). In other words, the rows are being shifted left/right (each colour channel independently). That’s why the image is rough along the vertical edges instead of being a nice straight line – sometimes, each colour channel is being pulled out of phase and dragged to the right, and sometimes it’s being pulled to the left (which causes it to wrap back to the right with inverted colours, because it’s interrupting the time slot that was dedicated to a different colour channel). Fun stuff to mess around with!

Noob Pancakes

Sunday, September 25th, 2016

This isn’t going to become a thing on this channel – I was just hungry and wanted to record it… I think I should stick to computer stuff. If I hadn’t put any effort into editing this, I would’ve put this on my other channel.

[Watch in HD]

If I hadn’t put any effort into editing this, I would’ve put this on my other channel.

Behind the goggles

Wednesday, September 14th, 2016

This explains a lot (maybe).

[Watch in HD]

Random Old Rubbish (Part 2)

Monday, February 29th, 2016

The second and much-shorter part, as I clear out some random rubbish in my room. There are a few more old electronic devices, including a ~25-year-old LCD game, plus some paper stuff…

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This time, I didn’t throw away or dismantle everything in the video! I did thoroughly rearrange whatever remained afterwards, though.

Random Old Rubbish (Part 1)

Saturday, February 27th, 2016

I was cleaning out my room and found a load of random stuff (mostly toys), and some of it was interesting, so I decided to record it. Some of it’s around 14 years old. I didn’t intend for 50% of the video to be about Beyblades.

[Watch in HD]

Stress-test Audio CD

Monday, February 15th, 2016

Never mind just gapless playback – let’s throw 99 tracks at various CD players (hardware and software) within 40 seconds and see how they handle it!

The music I used is “Nature’s Gasp” by Atmozfears & Devin Wild. Big thanks to Atmozfears for letting me use it on YouTube (now let’s hope that YouTube’s automatic song recognition doesn’t punish me despite that…).

[Watch in HD]

This test just naturally emerged after I played around with splitting tracks in a hardstyle mix for seamlessly playing on a CD. The trick to ensuring no silence between tracks was to split on CDDA frame boundaries (every 2352 bytes, which makes 75 per second for audio CDs). It took me some time before I realised that Audacity can measure position in CDDA frames and that I didn’t have to convert the number of samples into CDDA frames myself every time…

I don’t have a grudge against Foobar or anything – it really did get stuck in a loop of spinning up and down the CD the last time I tried it. Also, this may be my most anticlimactic and rushed ending ever.

Solar Panel Microphone (Experiment)

Sunday, January 31st, 2016

Here, I conneced a solar panel (via a transformer) to a sound interface as if it’s a microphone, to reveal the subtle pulsing and filckering of various light sources. If you don’t like 50 Hz, this video isn’t for you.

[Watch in HD]

Thankfully, the infrared light from my camcorder is apparently very clean (not pulsing), so I can use that to see things in the dark without affecting the sound.

The transformer is just designed to convert 230V AC to 12V DC, so its audio properties are not very good (it muffles things a lot). Ideally, I’d be using an audio transformer that’s designed to sound good, but this is all I had available. I am using it to remove the DC current that the solar panel makes, because I don’t fancy putting 17.5V into my Quad-Capture (sound interface)’s mic input. I originally tried to make a high-pass filter to remove the DC, using a capacitor and resistor, but it only worked until the capacitor became fully-charged, at which point the sound faded. It was much clearer-sounding than the transformer, but there was also a huge amount of background noise.

I want to revisit this idea in the future, especially to take it for a drive at night, listening to the street lights and car lights (since modern cars use PWM to dim the tail lights).

Clockwork Westminster chime striking 4 o’clock

Sunday, July 12th, 2015

Somebody requested this on my “Clock Overclock” video from my other channel, so here it is (better late than never, right? orz).

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Clock Overclock

Sunday, February 1st, 2015

The circuit board inside this clock died, so I replaced it with my laptop. You could say that the clock speed is about 70x the standard speed (this is the fastest the mechanism can handle before it just oscillates) – I’m impressed it can handle this.

[Watch in HD]

The headphone output is connected directly to the coil in the clock movement and driven with a square wave. The coil is 250 ohms – some headphones are much lower than this, so there’s no need to worry about damaging the laptop’s headphone output, either! The gears, on the other hand, may wear out a little quicker than usual. =P

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Fast open inkjet printer (HP Photosmart C4780 @ draft quality)

Friday, October 3rd, 2014

I had to open this printer to fix it for someone recently, and was impressed with its speed, so I recorded this quick and dirty video. I guess I should re-record it (making it print multiple pages), but I’m lazy. Maybe some day.

[Watch in HD]

The printer is an HP scanner/printer combination (Photosmart C4780). I’m impressed by the fact that it can still run with its scanner board disconnected.