Monthly Archives: November 2011

HD vs PTZ

I have to agree with the Luddites. Analog PTZ is far superior to IP MP Video. Especially if you need to really zoom in on tiny details, and you have a manned system…

…But that’s like judging a fish by it’s ability to climb trees (as Einstein supposedly said once).

Let’s flip it around, and ask how well an analog PTZ camera can look in two directions at once. Let’s ask if analog PTZ can do a tour at 90 degrees per second, 24-7-365 without breaking. Let’s try and do analog PTZ in Houston, from an office in New York on a shoestring. Let’s ask if we can change our minds and zoom in on a different area after the video was recorded.

Now, if an IP based optomechanical PTZ camera was given the same budget as the cost of wiring an analog one, then you would not be able to tell them apart at all. And I am guessing you don’t really need to spend the full budget to get equal performance – you can probably get good (perhaps not as good) performance a lot cheaper.

But what if you really wanted to replace a mechanical PTZ with a MP camera?

I guess a lot of installation were getting mechanical PTZ’s in the past because there was no other choice. Now there is. It’s fairly cheap to install 3 fixed cameras vs. 1 PTZ (simply because you don’t need to pull 3 cables all the way back to the recorder – you can pop in a POE switch and cluster the 3 cameras). If you then put in 3 decent cameras you are golden. You even get to see things from 3 vantage points – something PTZ will never do. Even if a vandal breaks one, you still have 2 others that are recording.

It is true that right now, the cost of 2 additional camera licenses are a burden, but I think that cost will come down dramatically over the next 24 months.

But a mechanical PTZ camera is really equivalent to a Gigapixel camera. If you do the maximum zoom level, and do a full pan-tilt of the area you get a huge resolution. If you were monitoring highways it would make sense to have an optical PTZ at the intersections which would allow you to zoom in much more than the MP would ever let you.

Another disadvantage to HD cameras are that they take up a lot of space and they require a lot of processing power to decode. This is mostly an issue for the client side developer (as we need to decode the frames to show them to you 😉 ), but an issue nonetheless. Some people will just compress the crap out of those feeds, but that totally negates the purpose. You might as well use a lower resolution camera then. Sometimes the framerate gets lowered to the point where you might as well be looking at a slideshow – but that might just be good enough for the user.

So I think Todd Rockoff is correct. HD and PTZ are complimentary.

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Preallocation of Storage

What is the principal argument against pre-allocating (formatting) the storage for the video database?

One problem that I am aware of is if you need to pre-allocate space for each camera. A camera with very little motion might record for 100 days in a 100 GB allocation, while a busy one might have just 1 day. Change the parameters and it gets real hard to figure out what a reasonable size should be.

But say that you pre-format the total storage you need for the entire system, and then let all the cameras share the storage on a FIFO basis. This way, all cameras would have roughly the same amount of time recorded in the database.

My, decidedly unscientific tests, show that writing a large block of data to a continuous area on the disk is much faster than writing to a file that is scattered across the platters. Disk drives now have large caches and command queuing, but these mechanisms were designed for desktop use, and not a torrent of video data being written and deleted over and over again.

Some people balk at the idea that you pre-format the disk for reasons I simply do not understand. If you have a 100 TB storage system, I would expect that you’d want to use the full capacity of the disk. There are no points awarded for having 20% of the disk empty, so why do people feel that pre-allocation is bad?

Any takers?

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NVR Integration and PSIM

Axis makes cameras, and now they make access control systems and an NVR too. Should the traditional NVR vendors be concerned about it?

Clearly, the Axis NVR team is better positioned to fully exploit all the features of the cameras. Furthermore, the Axis only NVR does not have to spend (waste?) time, trying to fit all sorts of shapes into a round hole. They ONLY have to deal with their own hardware platforms. This is similar to Apple’s OS X that runs so smoothly because the number of hardware permutations are fairly limited.

What if Sony did the same? Come to think of it, Sony already has an NVR. But, it’s no stretch of the imagination to realize that a Sony NVR would support Sony cameras better than the “our NVR does everything”-type.

In fact, when you really look at the problem, an NVR is a proprietary database, and some protocol conversion. To move a PTZ camera, you need to issue various different commands depending on the camera, but the end result is always the same: the camera moves up. Writing a good database engine is really, really hard, but once you have a good one, it is hard to improve. The client and administration tools continue to evolve, and become increasingly complex.

Once it becomes trivial to do the conversion, then any bedroom developer will be able to create a small NVR. Probably very limited functionality, but very cheap.

The cheap NVR might have a simple interface, but what if you could get an advanced interface on top of that cheap NVR? What if you could mix cheap NVRs with NVRs provided by the camera manufacturers, and then throw in access control to the mix? You get the picture.

If you are an NVR vendor, it is going to be an uphill battle to support “foreign” NVRs. If Milestone decided to support Genetec, it would take 5 minutes for Genetec to break that compatibility and have Milestone scramble to update their driver. Furthermore, the end user would have to pay for two licenses, and the experience would probably be terrible.

The next time an NVR vendor says “we are an open architecture”, then take a look at their docs. If the docs do not describe interoperability with a foreign client, then they are not open. An ActiveX control does NOT equate “open”. Genetec could easily support the Milestone recorders too, but it would be cheaper and easier for Genetec to simply replace existing Milestone recorders for free (like a cuckoo chick).

In this market, you cannot get a monopoly and charge a premium. The “need to have” threshold is pretty low, and if you charge too much, someone will make a new, sufficient system and underbid you. Ultimately, NVRs might come bundled with the camera for free.

So, what about PSIM? Well, we started with DVR (which is really a good enough description of what it is), but then we decided to call it an NVR to distance ourselves from the – clearly inferior DVR. Then we weren’t satisfied with that, so then it became VMS. Sure, we added some bells and whistles along the way (we had mapping and videowall in NetSwitcher eons ago), so now we call it PSIM. It does the same as the old DVR. I think this kind of thing is called “marketing”.

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