View Full Version : Video Multiplexer
5th November 2002, 07:31 PM
Surfing Eyesweb page I found a thing that i really want to have:
A Video Multiplexer that would enable me to capture 2 sources with one Capture card.
Link to Multiplexer description (http://www.infomus.dist.unige.it/eywindex.html)
Anyone dows know thins thing?
5th November 2002, 08:23 PM
Maybe you need a video splitter or quad box like this:
5th November 2002, 08:30 PM
Uhm, i already did search in this corner, but good quad splitters (25 fps, millions of colors) are still around 200-300 $
Our price $214.87
I hope i can build this multiplexer myself or buy it cheap.
It also outputs higher res and doesn`t eat up quality (most splitters work at resolutions like 512*512 - not very nice to capture)
7th November 2002, 06:40 AM
Hey meierhans if you get the instructions for building your own one, please let me know.
31st October 2003, 07:16 AM
Almost a year ago, but...
I'm now looking for a cheap (second hand) colour quad for my preview screens.
I'm considering to build it my own, but I don't find shemes for clour quads.
Meierhans, did you managed to build one?
Or someone else who's doing electronics, or studied electronics...
31st October 2003, 10:11 AM
multiplexers are really not very expensive, as they are so commonly used for security systems - keep a look out for some bankrupt stock or something like that as security systems often end up getting sold off real cheap.
2nd November 2003, 10:25 AM
the technique described on eyesweb is exactly the way all those 4port capture cctv cards work, there is one chip which takes full pal and the framerate is divided over all connected ports, furthermore you can preview up to 4 channels low quality, than pick one to be recorded full pal
sofort kaufen preis 72,00:D see ebay
4th November 2003, 12:52 AM
Damn one year. So much changed....
I didn`t build one, the eyesweb people never replied to my mails.
The bad point about these old security quad-splitters: Most of them are 256 steps B/W and give your 15 fps and digitize the video internally to odd resolutions like 512*512 . Looks really ugly after capture.
The tech used in eyesweb:
Home> Hardware and Software products>Video Multiplexer
Our proprietary special electronics board (Mpx) has been developed to capture concurrently the signal from two synchronized cameras. This board is based on the fact that we can multiplex two separate video signals in only one, by switchings between the two video signals at the field rate (50 Hz). In this way we obtain a new interlaced signal in which odds and even fields contain the two different signals. We can then acquire the signal using an ordinary full frame single channel acquisition board. At this point, we have in the frame memory buffer the two original signals, just missing half vertical resolution and halving the temporal resolution.
Hardware design by Matteo Ricchetti.
These cheap capture cards do not switch every frame or field but need much more time to switch. You get something between 5 and 15 fps + unregular intervals. The eyesweb hardware could serve 2 streams at full 25 fps but half resolution.
Right now I`m running 2 cheap haupauges in one PC, a bit limited but working.
I`m looking out for a cheap 4x multichip BT87XXX (they appear as 4 cards in hardware manager).
If I won`t find one... I hope Analog->DV Converter boxes will get a little cheaper (even if they have more lantency they are good for future lappy works)
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