jamhed and whatboy,
Don't get confused between chips and channels. A TW68xx chip can handle up to 4 inputs (that's why the driver labels them 'Composite 1' through 'Composite 4'). Board manufacturers like to talk about "Channels" (it sounds better). A single-chip card is often advertised as a "4-Channel card". However,
usually a multi-chip card will be advertised as a number of channels equal to twice the number of chips. In any event, a single chip can handle at most 25fps for PAL, or 30fps for NTSC. If a single chip is taking care of more than one camera, the chip's input must be switched back and forth between the different cameras, thus reducing the maximum framerate (and reducing by
more than half, because it take some time to do the switching).
You can look at your board and see exactly how many TW68xx chips are on it. I have a "16 Channel" card (8 chips), which looks like this (sorry, it's a high-res image, and my server is a little old and slow, like me):
http://www.bbrack.org/~bill/Techwell/img_0779.jpg
For that board, I get the following:
Code: Select all
[bill@bbi7a tw68-v2]$ lspci | grep 680
09:00.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:00.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:02.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:02.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:04.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:04.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:06.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:06.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:08.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:08.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:0a.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:0a.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:0c.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:0c.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
09:0e.0 Multimedia video controller: Techwell Inc. Device 6804 (rev 10)
09:0e.1 Multimedia controller: Techwell Inc. Device 6805 (rev 10)
[bill@bbi7a tw68-v2]$
and, after the driver has been loaded,
Code: Select all
[bill@bbi7a tw68-v2]$ ls /dev/vid*
/dev/video0 /dev/video2 /dev/video4 /dev/video6
/dev/video1 /dev/video3 /dev/video5 /dev/video7
[bill@bbi7a tw68-v2]$
I also have a single-chip "4-Channel" card. Similar listings look like this:
Code: Select all
[bill@bb64 tw68-v2]$ lspci | grep 680
04:09.0 Multimedia video controller: Techwell Inc. TW6802 multimedia video card (rev 10)
04:09.1 Multimedia controller: Techwell Inc. TW6802 multimedia other device (rev 10)
[bill@bb64 tw68-v2]$
and this:
Code: Select all
[bill@bb64 tw68-v2]$ ls -l /dev/video*
crw-rw----+ 1 root video 81, 0 2010-01-11 16:01 /dev/video0
[bill@bb64 tw68-v2]$
Regarding the ghosting problem, I'm quite sure it's unrelated to the previous postings on that subject. I believe there is a problem when more than one camera is connected to a single chip, and the application software (zoneminder) switches back and forth between channels. I'm still looking into that, but here's what my 4-chip interface looks like with one camera connected to each chip (one of my cameras is NTSC, the other 3 are PAL):
and here's the system status:
It's an Intel Core2 4-core system, and two people were monitoring the Montage view. There doesn't seem to be anything in the way of cross-camera interference, and (since each camera is being controlled by a separate chip, and separate video buffers are allocated for each chip) it would really be difficult, even for me, to get that screwed up.
I'll let people know if and when I find the suspected problem with channel-switching.
Bill