Post by thread:[EE]: rapid switching between two composite NTSC s

I have a stereo camera head which has two small CCD cameras, and can output the following NTSC signals: 1. One separate signal per camera, simultaneously outputting both signals (one composite signal per camera). I believe that these two signals have the same sync signals. 2. One signal that is interlaced as follows: Even fields from camera 1, odd fields from camer 2. I also have a head-mounted stereo display device which expects a frame interlaced NTSC input. Baically it displays FRAME 1 (two fields) on the left display, and FRAME 2 (the next 2 fields) on the right display. I would like to hook these two devices together in order to get real-time remote stereo input to my eyes. SO...What [I think] I need is a circuit which takes the two in-sync composite inputs, and alternates between the two signals to output a single signal which is appropriate for the head mount display. My plans are to get a circuit (any suggestions?) that can detect the start of a frame, and then with a little logic, switch between the two inputs. What I am concerned about is how this switching circuit will affect the sync signal on the outgoing signal. Anyway, I'm looking for input from anyone.. Thanks -Steve -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Hi Steve In effect you are creating an update at 15Hz on each eye which seems like a good headache generator if used for any period of time. Plus if there is any tendency for epilepsy you are operating at the upper end of a flicker rate that could induce fits. (Even worse in 50Hz regions where the flicker will be 12.5Hz). I would personally recommend using a dual link (either physically or virtually) and thus maintaining the 30Hz frame rate, Particularly if this is a commercial product and given the fact you are specifying a 60Hz product. However for Frame Extraction The classic IC is a Nat Semi LM1881 http://www.national.com/ However Elantec produce arguably superior products with the EL1881, EL4581 and EL4583 http://www.elantec.com/ Full Pin Compatibility with all products Regards Chris {Quote hidden}> I have a stereo camera head which has two small CCD cameras, and can > output the following NTSC signals: > > 1. One separate signal per camera, simultaneously outputting both signals > (one composite signal per camera). I believe that these two signals have > the same sync signals. > > 2. One signal that is interlaced as follows: Even fields from camera 1, > odd fields from camer 2. > > > I also have a head-mounted stereo display device which expects a frame > interlaced NTSC input. Baically it displays FRAME 1 (two fields) on the > left display, and FRAME 2 (the next 2 fields) on the right display. > > I would like to hook these two devices together in order to get real-time > remote stereo input to my eyes. > > SO...What [I think] I need is a circuit which takes the two in-sync > composite inputs, and alternates between the two signals to output a > single signal which is appropriate for the head mount display. > > My plans are to get a circuit (any suggestions?) that can detect the start > of a frame, and then with a little logic, switch between the two inputs. > What I am concerned about is how this switching circuit will affect the > sync signal on the outgoing signal. > > Anyway, I'm looking for input from anyone.. > > Thanks > -Steve > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> 1. One separate signal per camera, simultaneously outputting both signals > (one composite signal per camera). I believe that these two signals have > the same sync signals. > > 2. One signal that is interlaced as follows: Even fields from camera 1, > odd fields from camer 2. > > ... > > SO...What [I think] I need is a circuit which takes the two in-sync > composite inputs, and alternates between the two signals to output a > single signal which is appropriate for the head mount display. A stereo head mounted display already has two separate monitors, one for each eye. You should be able to use the two separate camera signals directly. The interleaved field signal is for single-monitor stereo displays that require a screen shutter, polarizer, shutter glasses, etc. ***************************************************************** Olin Lathrop, embedded systems consultant in Devens Massachusetts (978) 772-3129, spam_OUTolinTakeThisOuTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Your switching speed requirement is low. You have about half a line of time to switch over, that is 15 usec, and a 4066 gate will work. A circuit to detect the frame signal can be built by using a standard sync separator. This outputs an even/odd signal. By counting this with a flipflop you will obtain your required switching waveform. Peter PS: imho you are speccing the viewer wrong. Unless it contains a TBC it will flicker something terrific. Even if it does contain a TBC it will cause delay between what you see and what happens such that it will cause motion sickness and other problems with a simulator/remote manipulation application. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> PS: imho you are speccing the viewer wrong. Unless it contains a TBC it > will flicker something terrific. Even if it does contain a TBC it will > cause delay between what you see and what happens such that it will cause > motion sickness and other problems with a simulator/remote manipulation > application. "It's what I've got..." This is a one-off type of deal. We happen to have a stereo headmount display sitting around, and a stereo camera rig. They speak somewhat different signals, and I want to hook them together. Flicker does't seem to be a problem hen we use it "as intended" (ie watch the "3D" demo tape that comes with it.) I would classify this as a toy much sooner than I would classify it as a simulator / remote manipulation application. Anyway, I think it will work for what I want. Thanks for hte help -Steve -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics