#Where is PCI capture??
3 messages in this thread
I can think of 2 PCI capture cards. One from somebody like ThunderVision, MJPEG
640x480x30, not yet shipping. The other was from AITech. It does no compression
(better have a FAST disk array). Full studio quality video (even compressed)
overloads an ISA bus. Raw video is about 32 MB/sec. If you go 4x compression
(they say you can't do more without degrading quality slightly), it's still 8
MB/sec, too fast for ISA. Another BIGGER issue is the cpu ovehead of capturing.
If compressed to only 2/MB sec, that's still consumes a LARGE part of your cpu.
The ISA bus runs about 5.3 MB/sec, so that 2 MB/sec will probably consume about
40% of your processor, under perfect conditions. A PCI bus could deliver much
higher data rates with much lower cpu use. The cpu is then free to do the
appropriate houskeeping (initiating disk i/o, updating the preview window,
recording the sound, keeping the user interface responsive). – Jan
Jan,
Thanks for the information. I just got an AITech flier in the mail, and it has
the "VideoSurge-PCI" card listed. While it says "support all standard software
compression scheme", it does not mention hardware compression, as you say.
Does not sound too appealing at first glance.
I agree with your bus calculations that indicate the ISA bus speed can be a
bottleneck, so I continue to look for a mainstream PCI card. How about posting
your previous message on this thread to the Intel forum Video Capture section?
I posted a request there for a PCI version of the Smart Video Recorder Pro,
which was duly noted, but the response indicated that hard drives were
limiting, so an ISA card was not limiting. I replied that Fast SCSI II and
EIDE rates were now exceeding the ISA bus capacity, but your informed message
could also help Intel and others realize that it is time to get on with PCI.
What do you think? Regards, Robb.
PS. I hear there is a Matrox Marvel II PCI capture card, will see what I can
find on the Matrox section of the Graphics Vendors C forum. REO.
My guess is the Intel SVR may be performance limited in it's hardware
compression speed. I know LSI Logic makes two different lines of their JPEG
compression chips, the cheap ones and the fast ones. The cheap ones can only do
320x240x30fps or so. This ends up being about a 8 MB/sec uncompressed data
rate. The good LSI Logic JPEG chip can do 640x480x30fps. This takes an
uncompressed data rate of 32 MB/sec. The boards using the cheap chipset are
about $600 or so, the ones using the good chipset are $3500 or so. Unless the
costs of chips is much lower for Intel, they probably can't deliver much better
performance than they do, in the $500 price range. For 320x240x30fps with
hardware compression, the ISA bus is about fast enough. A question will be, can
we expect low cost, high performance compression chips from someone. If they
happened to have a PCI bus interface built in (getting quite popular with video
chip companies), this would be about what we want. – Jan