Transcoding for Security Video

Technology leaps in video security are often fueled by developments adopted from large dollar markets like entertainment. The use of transcoding and format down sampling in the DynaView SOC Video Management System are good examples of this approach.  This article offers a good discussion of the power and value of these techniques.

The Evolution of Transcoding

For live video streams used in security and surveillance applications on demand transcoding and format conversion offer substantial reductions in wide area network utilization while requiring practical levels of server and router power.

Wither Goeth Windows?

As our last post here for 2008, it seems fitting to discuss the fate of Windows and, indeed, the operating system in general. Vista as discussed here in Ode To Windows for example, has been pretty much a flop. I love the phrase incompressible failure in the article.

The decision to avoid Vista in DynaView systems was a good one.  On the other hand, Windows 2008 server (ironically sharing much of Vista’s core but little of its flashy facade) is poised to become the de facto standard server O/S.  Some even advocate its use on workstation desktops.

Another chirping chick is Google’s Chrome browser which intends nothing less than making the Operating System irrelevant. And, even Apple has gained some corporate share.

Whenever you start to think everything is cast in stone and the “big dogs” have a lock on the market, think again!

Interesting times for those involved in mainstream computer technology. Happy new year!

Basics of WLAN Antenna Selection

During the recent engineering and completion of several wireless LAN (WLAN) system, I realized that a common thread existed concerning the selection of antenna types in order to best meet stated design goals.

I have summarized the basics of antenna theory as it applies to this problem in a short illustrated white paper.

Although some familiarity with terms such as dB (decibels) will be helpful, the above paper should provide understanding for anyone with a basic techincal background. Anyone wanting a deeper understanding of decibels and RF power can review this Cisco discussion.

Megapixel Evidence

Most are familiar with the process of exporting captured video archive as an AVI file using the facilities built into DynaView. This process becomes a bit more challanging when dealing with megapixel archives. Often the area on interest is only a small part of the entire image. Converting a large number of complete megapixel or multi-megapixel images can result in unmanageably large AVI files.

A better process can often be used as follows:

1. Export the desired time interval from DynaView vPlay as a series of JPGs
2. Perform a batch crop operation using a program like XnView to select the desired area
3. Convert this cropped sequence to an AVI file using DynaView vMovie

Some further notes:

Try to use a standard crop size like 320 x 240 (CIF) or 640 x 480 (4CIF) to capture the area of interest.

It is possible to “follow the action” by cropping various sections of the exported JPG sequence with the same crop window size postioned differently.  This will appear as a jump cut in the final movie.

When converting a small crop area to AVI, try using vMovie to up-sample by 2X (for example, using 640 x 480 as the output size for 320 x 240 cropped JPG’s) during the conversion as this will often produce better results than expanding on playback.

Use the (free) DIVX codec from within vMovie to create smaller high-quality AVI files. DIVX is also an extremely fast compressor in comparison with any standard Windows codecs.

Always keep the original  video archive aside as part of the chain of evidence and bear in mind that the basic validation will be human affidavits confirming the continuity of that chain of evidence. Complete the entire process in one session and do not leave a window of time where someone else could make changes. Burn the results including the original archive on a DVD and keep it in a safe, with a lawyer, or on your person.

XP Service Pack 3 blocks .NET security patches

Many IP network solutions run on Windows XP and some of those use Dot Net. This article is worth review

http://windowssecrets.com/2008/12/04/03-XP-Service-Pack-3-blocks-.NET-security-patches

DynaView does not use Dot Net and DynaView SOC does not use XP Pro, so we neatly avoid this problematic issue.

Great System Demonstration

Some testing today has confirmed that it is possible to run a basic version of DynaView direct from an installation on a USB Key. The complete installation is well under 100 Megabytes so just about any key will work. Once this installation is made to the key (or copied to the key from any other running machine’s /nvr folder) it can be used by inserting it into any windows XP or better machine. Then, navigate to vMaster.exe and double click to start. Any module configurations and cameras licensing that were present will be lost but the system will work in 4-camera demo mode.

You will need to “re-configure” including resetting all module IP addresses which takes a minute or so. But, if your source for the install was a running machine on the same network, even the cameras data will be intact and valid except for the machine names and configurations of vCapture and other modules.

It is also possible to set up file-based demo cameras on such a USB key or even run VGen for live images.

Do bear in mind that some of the special facilites like CamPatrol and Scheduler depend on installation of windows services and may not run.

This is by far the quickest and easiest way to do a live demo short of bringing in a working machine.

High Power PoE Test Drive

Today’s lab work included testing the combination of the Microsemi (Power Desine) PD-7001G 30 watt mid-span PoE power injector and the same company’s PD-AS-701/12 30 watt high powered PoE splitter. These devices are well suited for use with cameras like the Axis 215 PTZ which require less than 25 watts but more than the 12 watts available from 802.3af systems.

Our real-world testing included a pair of the above devices plus a Kill-A-Watt AC power meter, a 12 ohm 50 watt load resistor, a DC ammeter and a DC voltmeter. Results as follows

AC Power – 15W @ no load, 30W @ full load
AC Volt-Amps – 27VA @ no load, 48 VA @ full load
DC Voltage 12VDC @ no load, 11.85VDC @ full load
Load Test Current 1.85 amperes
Load Power 21.9 Watts
Overall efficiency 73%
Injector Final Case Temp ~100F
Splitter Final Case Temp ~120F

These devices require free air flow and should not be buried under any type of insulation or barrier. The power available is more than sufficient for the Axis 215. Here is a good table of applicability of high power PoE to various Axis cameras. This table suggests that the 701/24 can provide power for the even larger 232D+ or 233 PTZ cameras. Do bear in mind it will NOT run the heater/blower in an outdoor dome.

RAID 5 May Be Doomed in 2009

A story appearing online is forecasting the doom of RAID 5 in 2009. Apparently with storage capacities of modern SATA hard drives now reaching 2-terabytes in size, the odds of a read error during a RAID 5 disk reconstruction is becoming unavoidable.

Power over Ethernet – Plus

Most new IP based security cameras allow for Power over Ethernet (PoE) operation and this is now established as a way to reduce installation cost while improving reliability and easing management’s job. Since 802.3af PoE is limited to about 12 watts maximum load, the operation of PTZ cameras is generally considered beyond the scope of the method. While the pending higher powered 802.3at standard is still but a future promise, all is not lost.

Many of the newer PTZ cameras (such as the Axis 215) can be run on DC power and require less than 25 watts. There are several companies (such as Power Designs and Phihong) that offer external (midspan) power injectors and splitters that can easily deliver enough power for such cameras.  The site Power Over Ethernet is a good resource for information on this equipment.

We have completed several project designs using these high powered PoE systems with good results and large savings in installation costs.  Keep this idea in mind for your next design or installation.

RAID1 – What Say You?

IPVideo Corporation has been manufacturing RAID1 storage options for its video management systems for the past year Our customers, particularly those that do not have the resources to effectively monitor total system performance, have found RAID1 to be a reliable and user friendly approach for critical storage.

Some of the reasons IPVideo Corporation recommends RAID1:

All data is mirrored on both hard drives in the array for redundant protection of all recorded video. This is normal data, no striping.

RAID1 provides a simple rebuild process; upon hard drive failure, plug in a new drive and walk away. No user intervention required.

RAID1 allows the user to remove a hard drive at any time without causing any downtime. Users can provide authorities with the actual hard drive the video was recorded on, retaining the chain of evidence. Video can be played back on any PC with USB attached drive carriage.

RAID1 will auto-rebuild. Video will continue to store normally during array rebuild process. No particular vulnerability. RAID5 takes a significant amount of time to rebuild in the event of a failed array. RAID5 is in a degraded state during a rebuild and is vulnerable to data loss in the event of a second drive failure. The data is also vulnerable to loss until all the data that was on the failed drive is rebuilt onto a replacement drive.

RAID1 stores fewer video streams per drive letter, this improves load balancing as compared to other RAID levels that consolidate drives on to one stripe or drive letter since Windows effectively uses the extra throughput of the extra physical spindles.

RAID1 has a lower failure rate. For example, consider a RAID 1 array with two identical models of a disk drive with a 5% probability that the disk would fail within three years. Provided that the failures are statistically independent, then the probability of both drives failing (with no replacements for 3 years) is 0.25%.

RAID5 configurations suffer from poor performance when faced with a workload which includes many writes which are smaller than the capacity of a single stripe.

If you have a comment or some insight into RAID options for security video storage we would appreciate hearing from you.