🚀 go-pugleaf

jeganath@leland.Stanford.EDU (Muthuveerappan Jeganathan) writes:
: Hi, I hope this is the appropriate news group for the following discussion. I 
: have a question regarding image transfer from frame grabbers to PC RAM. I am 
: interested in capturing a 1k x 1k x 8 (1 MB) image from a CCD using a frame 
: grabber. At what rate can I dump these images from the frame grabber on to the 
: PC RAM or possibly a SCSI hard disk. If the CCD operated at 5Hz frame rate, is 
: it possible to transfer all 5 MB to the RAM in a second? I have been told data 
: transfer is limited by the PC bus. Is this true? How about with a DMA transfer?
: If the answer depends on the system, what are the typical transfer rates for
: a 486 50 MHz PC with 64 MB RAM and 1 GB SCSI HD.
: 
: Any help is appreciated. Thanks. By the way, if this would be more appropriate
: for another group let me know. I cross posted this on sci.image.processing.
: 
: -- Muthu Jeganathan
Well as they say - the mileage varies.

A memory to memory copy (Frame Grabber to PC RAM) would probably
transfer at about 3 to 4 MB per sec max on a 16bit bus and 1.5 to 2MB
per sec max on a 8 bit bus.

A DMA transfer (if available) is not much faster. These movs instructions
for the 486 are pretty efficient.

Unless your app requires very good resolution (and if your CCD camera is
pretty good), one option may be to decimate the image. (ie subsample 
the image). a subsample of 4X may not affect the image by much.

Typical HDD speeds range from 400KB to 4MB/s depending on the HDD
and the access pattern. You may want to preallocate your files to
optimise seeks. (I heard there are new super fast SCSI HDD available so
I added in that upper limit). The best is you test your HDD.

Since you have 64MB RAM, the best alternative maybe to simply stream all
your data out to RAM first then do offline storage. 64MB can store quite
a few seconds of data esp. if you combine it with temporal and spatial
subsampling.

hope this helps

jin meng