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---------- Forwarded message ----------
From: Fred Moore <fmoor at fmeco dot com>
Date: Mon, Feb 22, 2010 at 11:54 PM
Subject: Re: [Leaplist] Linux configurable ip surveillance camera systems


Dan Cherry wrote:
> Anybody have any experience with ip based surveillance systems?
>
> D-Link has some reasonably priced hardware, but the initial set up is
> through Windows.
>
> Also, has anyone any thoughts on Linux accessible surveillance dvr's
> (vs. feeding IP camera output directly to a PC for storage)?
>
> I'm considering 4 cameras with a dvr expandable to 8 cameras.
>
> Finally, should I just fall back to older analog cameras that feed
> into a DVR that is IP accessible?  That seems like the best bang for
> the buck, but the least flexible.  Hmmm, come to think of it, how much
> flexibility do you need in a video surveillance system?
>
> Any thoughts on the subject would be welcome,
> Thanks,
> Dan
>

Do that for a living..  My knowledge is yours for the asking.

Don't think about Web cams as they are not good IP cameras they don't
get you to a codec till the high bandwidth video gets to the computer.

Camera Trade offs,  CCD vs CMOS imager, and size, equate to quality,
light level, streaming rates, and video compression at cameras.
Personally I would never install a CCD imager camera, but 90% of the
camera's on the market use this technology, why because of the advent of
phones with cameras built in.  The CCD imager has forced a huge price
reduction.  Don't know where you live, but I can show you the difference.

DVR.  "Digital Video Recorder" (not for recording IP camera), DVR's have
analog video input.  Almost all DVR hardware have A/D converters on
input.  Mostly not good deals because of the unknowns internals (more
explained next).  Stay with Analog or IP, and don't mix them.

Most  DVR, start with a 4-CIF video image (input), only to have it
immediately  reduced to a 1-CIF image via pixel trashing, then run it
through a lossy codec and store it, in MJPEG,  in MJPEG every frame
carries 100% of the infomation and the storage goes way up compared to
MPEG4, H.264 etc, when you reach these codec's you input 1/4 the image,
and move to P/I frames.  P frames very from recorder to recorder if we
assume a P frame of 1 second and are streaming at 15 FPS, recording
looks fine in playback but suddenly rewind viewing, and searching is
very ugly why because the I frames can not be reconstructed backwards,
so rewind is a hideously jumpy 1 FPS image.  The problem is you don't
know on cheap junky recorders what they are doing inside at the codec
level.  Take H.264 "best bandwidth compression" we have,  While the P
frame rate is part of the standard, some recorders are doing P frame
rates as far out as 15 seconds, unless they see movement and then they
record more P frames.  Why? they don't have the processing power, or the
storage capability to store it properly.  All of this costs money.  This
is not goodness.

Flexibility: unless you have something with good analytics, you don't
have a security system, you have a recording system. Security systems
notify of something going wrong, or at the very least have a mechanism
which will flag the recording of an event.  Otherwise if you want to
know when something happened, start watching 24 hours/day of recordings.



Analytics like, motion, virtual fences, Image identification (car,
person), camera moved, camera shaking, identification are all
availability.   The better they are the higher the costs.  Most simple
motion analytics at the camera fall down when place outside and the wind
is blowing, or it is raining.  No camera manufacture has resolved this.
Good VMS (Video Managements Systems) have solved this years ago, can you
say processing power?  The higher resolution of the camera, the more
processing power it takes.

I deal with things like virtual video fencing, and image recognition
every day.  Its all processed at the VMS, why Camera's can distinguish
movement, but was it a bird, dog, person, car, rain, or wind.  Depending
on quality you can go from 1000 alarms/day to view or search, or 1 real
event per day.  Cost is the difference.

There are a couple of Linux solutions at the VMS level, but don't
recommend them.  All I know of want to also be compatible with windows,
unix, Mac..  can you say Java.

Some of the things to consider.
codec between the recorder and the camera?  codec's are the trade off
between  network bandwidth, resolution, storage requirements, and
processing power.

D-link is total junk, it is built for 1-CIF camera's (1/4 analog
signals), if you are going IP you need 1D capability, and the horsepower
to manage it, or there is no reason to go with IP.

This is a huge topic, or we can move it to BS as this is not Linux
centric.. I will assist you if you give me some more information or give
me a call..  cell <deleted> Regards.. Fred


--
Lots of soaring generalities, without a single hard fact in sight. Saves
the trouble of having to do research.
Fred/WD8KNI

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