> I think Eric has a point. Even with you calculations below, I think the
> bottleneck is you hard drive. Write rate is slower than read rate.
> 13MB/s write rate for a single disk is doing very well.
>
> Ed.-T.
I agree Write is slower than Read, but his numbers don't seem all that out
of the ball-park, depending on his drive.
testing my video capture box (Dual PIII-1Gig, 512Mb PC133 RAM, dual Quantum
Atlas 10,000 RPM drives (one disabled for test) w/29160 Adaptec SCSI-160
controller) I post numbers consistantly higher than 13MB/sec write, actually
rather substantially higher, more than double on a long sustained write
(like we'd see for video) -
Test File: "/$$test$$.tst"
Test File Size: 6400 MB
Testing Uncached Write Speed....
Data Transfer: 27.19 MB/s, CPU Load: 0.8%
Testing Uncached Read Speed....
Data Transfer: 21.89 MB/s, CPU Load: 0.4%
Testing Cached Write Speed....
Data Transfer: 17.89 MB/s, CPU Load: 2.0%
Testing Cached Read Speed....
Data Transfer:179.67 MB/s, CPU Load: 0.4% (PHEW!)
I'll also admit that this is skewed some-what out of the park of common
consumer machines... If we're talking about a 5400 RPM IDE-33 drive, all
bets are off. [grin]
But now on to the real question here for a moment: NTSC resolution is what,
480x704 x24bits x30fps (merged-frame/deinterlaced), right?
My numbers for full-screen, merged-frame/uninterlaced, non-hardware assisted
capture would then be 480 lines x704 pixels x24 bpp x30 fps or around
238Mbit/sec, which is about 30MBytes/sec, worst-case, right? Which would
explain why I like my winnov card doing 2:1 hardware compression taking me
down to about 15MByte/sec, or enough to reliably get the data onto the
drive.
Did I make some huge mistake here?
--- Jodie Reynolds, CTO
Interact Devices, Inc.
