Linux Journal: Amateur Video Production Using Free Software and Linux

“The first obstacle I encountered in my work to convert my
videos was how to digitize the analog VHS tapes. Because I wanted
to convert standard analog video tapes, IEEE 1394 (Apple calls this
interface FireWire; Sony calls it i.LINK), though extremely
powerful, defines a purely digital interface and would not suffice.
Instead, I decided to purchase a video capture card. Many vendors
produce these cards, which take standard analog video streams and
digitize them for storage or display on a computer. I bought
Hauppauge WinTV PCI video capture card that works nicely with Linux
for around $80 US. Incidentally, the Linux driver framework for
video capture cards is named Video4Linux.

“There are a few important considerations to make when
purchasing a video capture card, though they are becoming less
relevant as the speed of computers continues to increase. Because
capturing video from most analog sources must occur in real time,
writing raw video to disk requires a very fast hard drive. In my
experience, even a 10,000 RPM SCSI drive has difficulty storing raw
24-bit video with a resolution of 640 x 480 and a frame rate of
23.9 frames/second. Think about it: around 30 frames per second,
640 x 480 = 307,200 pixels per frame, and each pixel is 24 bits. In
order to store uncompressed video of this quality, a hard drive
needs to write 2.21 x 10⁸ bits, or around 26MB every
second!

“Don’t run out and buy an expensive high-speed disk array quite
yet–an alternative exists. Compressing the raw video before
writing it to disk shifts some work away from the hard disk.
Compression can be done either by a dedicated processor, shifting
work to video capture card compression hardware, or in software,
shifting work to the system’s CPU. Since my system has two 1,000MHz
CPUs, my cheap Hauppauge card, which lacks compression hardware,
performs just fine. If your computer’s CPU is a little slower, it
may make more sense to invest in a video capture card with hardware
compression capabilities and save a relatively expensive CPU
upgrade for later…”

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