Re: Help: searching a video server that meets my requirements
- From: Paul <nospam@xxxxxxxxxx>
- Date: Sun, 20 Jan 2008 03:32:08 -0500
heikens wrote:
Paul, Green,
Thanks for your reply. Searched a bit further on the internet on the
things you mentioned.
A problem that I found during my search is that there are a lot of
video server/capture devices out there, but most of them provide their
video stream via a webpage generate by the server. Viewing the video
via VLC or quicktime is not possible. You can only find this out by
reading the user manuals.
Found another video server from AXIS though. After consulting with the
sales deparment, it seems that the video stream can be viewed using
VLC.
http://www.axis.com/products/video/video_server/index.htm
Huub
Did you check the price ? Anything that mounts in a rack, is
bound to have a high price. (Because business users have
infinite bank balances, apparently.)
If this is for personal use, and not a corporate/business
application, you can probably build your own server device
(use Linux as the OS), and make your own server. That way,
it'll stream in whatever format there are open source drivers
and software for. That could end up being cheaper than a
ready-to-go rackmount solution. It all depends on cost
versus time tradeoff.
http://www.videolan.org/vlc/
I'd probably pick up some cheap BT878 based cards, with
composite input connectors, and put something together
that way. The BT878 has drivers around for it.
For basic composite capture, Ebay (Hong Kong sources) has
capture cards. What you see here, is five chips. Four *could*
be BT878 chips (640x480x30FPS per chip). The fifth chip
is a PCI to PCI bridge chip, so there aren't four loads and
bus stubs from the BT878 on the computer main PCI bus.
http://cgi.ebay.com/4-CHANNEL-CCTV-DVR-120FPS-SECURITY-VIDEO-CAPTURE-CARD_W0QQitemZ230214784796QQihZ013QQcategoryZ88755QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Those cards also appear as "16 input 4 chip" versions, but
they don't capture well from all 16 inputs at the same time.
They "time sample", moving from camera to camera. That
is why, the above PCI board with only four connectors, is
closer to a "real time on all channels" type device.
The above card will saturate a PCI bus, with its 133MB/sec
bus transfer limitation. That is because the cheap capture
cards don't use compression. Which means, you cannot buy a
motherboard with five PCI slots, and have 20 camera capture
capability in the same computer. If you want a better
density solution, then the capture card would need to
use compression first, to reduce bus traffic. That
drives up the capture card cost substantially (as the
above card should be well under $100). It also complicates
the driver issue, if you wanted to use Linux.
In any case, if you were building a Linux box, you'd
want a hardware card that has Linux drivers available.
There are USB composite capture devices. Which would be
another way to get capture into the box. If uncompressed,
there would still be bandwidth limitations (60MB/sec
per USB2 root, shared over all motherboard ports). The
USB capture devices I'm aware of, use some form of compression.
Adding USB cards to the computer, increases potential USB
bandwidth, but some OSes have limits as to how many
USB chips they'll support (so check that first). This
is an example of a PCI Express based USB2 card, which
would allow a PCI Express motherboard to be used.
SYBA PCI-Express USB 2.0 5 Ports Controller Card Model SD-PEX-NEC5U - $30
http://www.newegg.com/Product/ProductReview.aspx?Item=N82E16812186010
(Note - 60MB/sec per card limit. Four ports at 15MB/sec each max.
Should not be a problem for a compressing video capture device.
PCI Express is not the limitation here. The limitation is the USB2 chip.
But because PCI Express slots are independent, you can use more than
one card, without old-style PCI bus saturation.)
The USB capture device you used, would also need a Linux driver.
Since I'm lazy, this isn't the best one, merely the first device
I could find. Device has hardware compression inside the box.
This product would likely be discontinued, due to the analog
TV tuner inside, so you may not be able to find this particular
one soon. (I did find a list of other similar devices though.)
WinTV-PVR-USB2
http://www.hauppauge.com/pages/products/data_pvrusb2.html
http://groups.google.ca/group/comp.os.linux.hardware/browse_frm/thread/d6c7903017c1fbd7/e9bbc86692525394
Hauppauge WinTV USB 2 (em2820/em2840) [2040:4200]
Notice in the list here, a large number of USB2 alternate designs.
Video 4 Linux (V4L) driver of some sort.
http://groups.google.ca/group/linux.gentoo.user.de/msg/e2c441c7a2f5c272?dmode=source
PCI Express is a great solution in terms of breaking
the bus bottleneck. Trouble is, nobody seems to be
latching onto the opportunities. You could place
a lot more capture chips on one card, as each PCI
Express slot offers independent bandwidth. Even a
PCI Express x1 slot offers 250MB/sec, which would allow
at least four cameras per slot without complaints. (And
*close* to eight cameras could fit. I'm not sure of
the percentage overhead on PCI Express, to work out an
exact number.)
But I don't see a "Hong Kong" card in the current Ebay
lists, to do that. It should be dead simple for them to
make.
Conexant has a capture chip with a PCI Express interface
on it. I think Hauppauge has a card based on that chip.
But the Hauppauge card only captures one camera, so if you
filled all available PCI Express slots, you would not be
much further ahead in terms of server density.
http://www.conexant.com/products/entry.jsp?id=454
Just a few ideas,
Paul
.
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