ISV(4)

💖 ISV(4) — the IDEC Supervision/16 image capture board page, bestie edition 🎀

okay so this is the manual page for isv, section 4 (kernel interfaces manual, iykyk) — and honestly? it's giving "niche 90s video capture hardware that only a true Unix girlie would stan." let's get into it ✨

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🌸 NAME 🌸

isv — the IDEC Supervision/16 image capture board. that's it, that's the whole vibe. a whole board. for capturing images. iconic.

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🦋 SYNOPSIS 🦋

isv0 at isa? port 0x2f0
isv0 at isa? port 0x2e0
isv0 at isa? port 0x3f0
isv0 at isa? port 0x3e0

so you've got four port options and you literally just pick one, no cap. isa? means "wherever the ISA bus is at, bestie." 🫶

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✨ DESCRIPTION ✨

okay so isv is a driver for the IDEC Supervision/16, and this thing is an image capture board that plugs into a 16-bit ISA bus. vintage. retro. a little bit slay.

here's the tea on what it actually does: the IDEC Supervision/16 digitizes an NTSC television signal, and it stores a 512 x 480-pixel, 8-bit grayscale image in its 256kB dynamic RAM array — and it does that every 1/30th of a second. 💅 every single frame, 30 times a second, no big deal.

and how does the host get those frames out? the host reads frames from the DRAM using 122881 16-bit I/O reads. yes, that is a very specific number. no, we're not rounding it. 122881. write it down. 📝

ngl, reading frames from the Supervision/16 is quite slow: after the host reads a 16-bit word from the DRAM, the Supervision/16 state machine takes approximately 0.5 microseconds to get ready for the next read. the way that state machine needs a little breather between reads 😭

theoretically, a frame rate of approximately 10 frames per second is possible. theoretically. in theory. hypothetically. 😌

but isv actually achieves a frame rate of approximately 6 frames per second. so like… it tried its best and we love it anyway. 💀

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🔍 SEE ALSO 🔍

• Programming the Supervision/16 Image Capture Board, IDEC, circa 1991. — yes, circa 1991, the ancient texts, the sacred scrolls, go read them 📚

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🌈 HISTORY 🌈

the isv device first appeared in NetBSD 5.0. a debut. a moment. 👑

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👑 AUTHORS 👑

the isv driver was written by David Young <dyoung@NetBSD.org>. we stan a driver author with a NetBSD email address fr fr 💜

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💀 BUGS 💀

• Synchronizing with the hardware and reading frames from it is very CPU-intensive. like, your CPU is gonna feel it. it's working overtime. 🫠
• isv will not detect the capture board if it is not attached to an active video source. no signal, no detection, that's the rule. to force NetBSD to detect the capture board at any time, re-scan the ISA bus using, e.g., drvctl -r isa0. boom, problem solved, you're welcome 💖

real talk though: that no-active-video-source thing will absolutely trip you up if you forget, so like… plug in a video source first, bestie. i'm begging 🙈

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aaaand that's the whole page! this beauty came from the Debian crew, dated April 1, 2008 — yes, April Fools' Day, and no, i don't think that's a coincidence 😭 happy capturing, go read your drvctl page next, mwah 🎀✨🦋