Which card are you using for this? I have just such a need. I do not need to keep the images, nor do I need a high rate. But, I would love to get four images from one card! With, it seems, 4 connectors. On Thu, 28 Aug 2003 09:29:54 +0100 "Matt Brocklehurst" <Matt.Brocklehurst@xxxxxxxxxxxx> wrote: > Hi, > Ive managed to finally get my V4l program to get a semi-good frame rate > (4fps) over 4 cameras on a single chipped bt878 card - displaying this > to screen no problem - however im at a loss how im going to dump the > camera images to disk! Anyway ive tried the fps drops off to something > icky (like 1fps). Any ideas/suggestions - source code would be nice! Not > too bothered about the format - as long as i can convert it at a later > date to jpeg no problems, just want the fastest way of dumping the data. > > (Was thinking about threads - did attempt this but didnt seem to get > anywhere :( ) Threads are not necessarily faster. Depends on what you are up to. I do jpeg compression in one application and that helps alot. However, that is using a firewire digital camera providing YUV images. Still, the application stupidly converts these to RGB before passing it to the JPEG library, which I think converts them back (correction is on todo list). And the system keeps up while doing a ton of other things. We cheat and do not re-calculate the Huffman tables for each image. That also helps decrease conversion time. What type of hard disk are you using? We use good SCSI disks for these types of things. The performance improvement is noticeable. If you are using IDE disks, the CPU conversion to JPEG may actually offset the decreased data to be written. -- +····························+·······························+ · Roger Oberholtzer · E-mail: roger@xxxxxx · · OPQ Systems AB · WWW: http://www.opq.se/ · · Erik Dahlbergsgatan 41-43 · Phone: Int + 46 8 314223 · · 115 34 Stockholm · Mobile: Int + 46 733 621657 · · Sweden · Fax: Int + 46 8 302602 · +····························+·······························+
