ZoneMinder Forums

I am planning retail installations (24hr Day Care and Convenience Store) which request continuous recording on the cameras, and event storage for up to ten days. My question, is there a standard framerate for security? What FPS does an extended (12/24 hour) recording vcr use? I am seeking recommendations for the minimum FPS and jpeg compression settings in zoneminder.

Time lapse VCR's record different framerates depending on the capacity you want to get out of a tape, up to around 960 hours -- so it is based on how often the client can tolerate changing the tape, and their overall security requirements. Some time lapse systems can run at realtime when motion events are detected. There is no "standard" because everyone has different requirements.

As with most things, it comes down to a compromise between security needs and budgetary requirements. You need a cost analysis to determine framerate & quality & storage retention vs. implementation cost. If you have not already installed ZM, set it up with one camera as a test system. Experiment.

Video is really low resolution. Higher framerates often help make up for that. Play around before you make any big decisions.

I understand the key to the issue is finding a acceptable level of quality vs quantity.

I have a Gentoo system running zm-1.19.4 with 1 camera. I have found that 4 fps is the lowest framerate that I consider acceptable for video, less than that and movement is really choppy. Furthermore, a color camera at 320x240 using 70% jpeg quality results in an average frame size of 17.8kb, 60% is 15.1kb, and 50% is 11.9kb. (100% jpeg compression was 88kb, yikes!)

Using this data I calculate the following.
1 color camera, 320x240, 4 FPS
70% jpeg compression requires 256.32MB an hour
60% jpeg compression requires 217.44MB an hour
50% jpeg compression requires 171.36MB an hour

A week with 8 of these cameras would require 230.31GB.

Yet the following 8 camera system claims to store 30-60 days of "high quality" recording in a pc with a 120GB drive! http://gallery.bcentral.com/GID5064606P ... VR8-8.aspx

Am I expecting too high of a quality/fps, or am I missing something?

What framerate and jpeg compression level are other people using?

Should I just throw more hardware at it, like a 1TB RAID?

The DVR8 kit you mentioned probably uses MJPEG, MPEG, or some other motion-based compression algorithm. You will naturally get much better compression rates doing that than by just storing JPEG frames. One solution is to convert "events" from JPEG to MPEG. If you have a continuous monitoring setup you might be better off capturing MPEG or MJPEG in the first place.

I am personally dissatisfied with JPEG at quality levels below ~ 70-75, and I am often hard pressed to tell the difference between 90 and 100. If I will be transcoding to MPEG, I use a higher quality level for the JPEG frames than I would if I was planning to keep them as JPEG forever... The reason being the extra quality lost during the conversion.

Another way to cut file sizes fast is to use B&W. You get higher resolution, better light sensitivity, lower cost, and much smaller files. But I am sure that isn't news to you. I plan to use a mix of color and B&W cameras in my environment.

Given the low cost of 250gig drives, personally I would be inclined to do as you said, and buy four, along with a 4-port 3ware controller, and use RAID 1 or RAID 5. That would give you 500-750gig of storage along with some fault tolerance.

Remember, a 320x240 RGB color frame is 225k. A B&W frame is 75k. JPEG is doing a good job!

Concerning transcoding to mpeg...
I am using the '-sameq' option in ffmpeg which prevents ffmpeg from compressing the frames. Danger - This results in an mpeg which is larger in size than the total size of the jpegs.