I do some work for a machine vision provider and help them with interfacing cameras, sensors etc. to the digital I/O which is provided on some frame-grabber cards. If you're 'in' at the design stage then some uncommitted digital I/O would be very useful IMHO. The cameras they use have TTL triggers for capturing images and also RS232 for remote configuation by the host PC. Nigel Duckworth Frame grabbers www.imaging.com Cameras www.jai.com ----- Original Message ----- From: "roines reenig" To: Sent: Wednesday, May 26, 2004 6:43 AM Subject: [OT:] hardware for video capture > > Hi all, > > I'm getting a chance to participate in the design of a motherboard. The board has several features including all kinds of audio stuff, some proprietary interfaces and networking support. I'm thinking of adding one more feature which is support for video decoding. > > From a usage perspective, the board will have (at least) 4 BNC (coax type) connectors on one side. The user would then hook up their external cameras to that. I'm hoping to support all kinds of cameras. From going through catalogs, it looks like there is quite a range and the common factor is the use of analog output formats such as NTSC/PAL. The cameras range from the USD$20+ CMOS kind to the high quality USD$80 CCD kind. So from that datapoint, I conclude that I need to add a video decoder to this board. > > From a bit of research on video decoders, it became apparent that the most popular choice is the BT878 series from Conexant. These appear to be very simple to design in and include a PCI target/initiator in-chip as well as support for multiplexing up to 4 inputs. This seemed ideal to me. So I went out and bought a sample board that had a BT878A chip on it. Found the linux drivers, and wrote up a V4L client to capture frames as fast as it can, convert it from the 640x480x24bitRGB to 640x480JPEG(Q=75). Things were looking great. I then found a bit of software that captures these images and streams them over a webserver and includes support for multiple cameras. I found then, that with 4 channels using 640x480 and the CPU doing all the compression to JPEG, the performance dropped to about 3 frames per second per channel so 3*4=12 frames per second total. btw, that was on a Pentium-III 800MHz with 256MB of RAM. > > At first, I thought, well that's not too bad. Then I took a look at products from Convision and Axis. The convision product, i forget the name, was doing about 15 frames per second on 6 channels of incoming video. And the axis ip camera, about the size of a keychain, was doing 30fps through a web server. So now I have video envy. :-) > > So I popped open the convision product quickly and saw that it was using a Zoran 36060 chip inside with some Lattice FPGAs. Now, I did notice that their board used a 486-DX cpu and looked like it was talking to the FPGAs through an ISA connector. Looking up the details of 36060, I see that it is a JPEG codec chip (thus alleviating the CPU from the biggest task of doing the per-frame compression), so you supply a video decoder (like a BT878 except you just use it to convert NTSC/PAL to digital 8 bit YCrCb) and it then puts out JPEG frames, and then you add on a PCI interface like the ZR36067 which would drop those frames into your main memory. So my current thought is that I should use that combination but then I run into complexity because I would still need a video decoder chip. I could use a BT878 but that would be a waste since I'd have redundant functionality. So to restate the problem, I'm looking for a way to get about 15fps per channel on 4 channels of video input, with as low > > a cpu utilization as possible. > > I figured, with the robot fans on the list, maybe someone might have some advice on the "right" way to design this. Any suggestions or even just random thoughts on the topic are welcome. > > Thanks, > Roines > > > > --------------------------------- > Do you Yahoo!? > Friends. Fun. Try the all-new Yahoo! Messenger > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads