24-hour VCRs

[zilog jones]

I've always wondered how these VHS VCRs for CCTV use work. Can anyone give some insight?

What kind of tapes do they use? Surely they can't be much longer than E-240 cassettes, as the tape in them is thin enough as it is. I assume they save on quality by recording in balck & white, but I also was wondering if either the audio track is still there or if the space is used for video too? And do they still record 525/625-line interlaced video?

[neo75903]

Think it takes a frame every x seconds and records it to a normal tape.
Recordings are usual shaky if you playback a security tape.

[Soulhunter]

I remember there is some sort of "endless recording" tape !!!

The end is "revert-folded" and assembled to the beginning...

Guess it records @ both sides, so that it loops forever !?!


Bye

[Doobie]

I think most people use standard VCRs on the slowest speed setting, along with regular tapes. Continuous-loop tapes would only be used by people where it's not practical to be switching tapes.

I'm sure there are some specialized setups that extend tape length by using a lower frame rate.

[zilog jones]

Well, the VCRs I usually see by CCTV monitors usually say something like "24 Hour Recording" or something along those lines, so I assume they do something special that normal VHS recorders don't.

I've heard of looped audio cassettes before, and can see the same thing being possible for VHS... but this would be totally useless for recording CCTV cameras! You'd be recording over the same 5 minutes or so over and over again.

[Soulhunter]

Well, I found a site (http://www.polarisusa.com/cgi-bin/product_listings.pl?listing_category_id=97) that sells this 24h VCR's !!!

Originally posted by zilog jones

I've heard of looped audio cassettes before, and can see the same thing being possible for VHS... but this would be totally useless for recording CCTV cameras! You'd be recording over the same 5 minutes or so over and over again.

Hmm, why 5 minutes ???

I thought of a 2-sided 6h tape that records @ LP, so you get 24h...

Ok, I have to admit that Ive never seen a tape that runs longer than 5h !!!


Bye

[neo75903]

hmm from that site.
Sanyo
TLS-4960
960 Hour Time Lapse VCR, 300 TVL, Color Half-Size Chasis

960!!!??? I think that is in a sort of images mode.

a 240min at lp can record for 8 hours. There are even 300min tapes, but these are to thin and vcr tend to rip those tapes.

[wmansir]

"Time Lapse" is the key, that means it only takes a single frame every 1 or more seconds. So an 8 hour tape (30fps) recording 1 frame every 4 seconds (.25fps) = 960 hours. Or it could do a half-resolution frame every 2 seconds.

I'm sure these machines are also built to be very durable since they are intended to be run 24/7 for years. The cheap consumer VCRs made today wouldn't last very long under those conditions.

[Mug Funky]

hmm... whenever they show security tapes on TV from 7-11 robberies or whatever, they're about 1 frame per half-second.

also, VCRs record fields, not frames. so it's possible to get a nice doubling of time if your fields are recorded half a second or more apart.

of course, it's not all that useful for identification purposes, but it's useful for figuring out chains of events, where and when, etc.

there's also usually a timecode in the top of frame, so if anyone's confused about the speed it's meant to be played back, you could always take a look at that.

[Fantasma]

Where I work we used to have one of this VCRs recording 24 hours using a normal Sony 6 hours Tape, the VHS is called "Time Lapse" Video Recorder as wmansir said. The equipment was setup using a device multiplexer to feed the recording of 6 cameras at the same time, so it was able to record live action from 6 different sources.

Play back was really ugly.

[neo75903]

switching between the 6 cameras i presume?

[Fantasma]

Originally posted by neo75903
switching between the 6 cameras i presume?

I am sorry, I am not understanding your question, but I guess you are referring to the way it recorded 6 cameras. the cameras were connected to a hardware multiplexer and the multiplexer to the VCR, on the screen you could see the 6 cameras displaying live picture.

Hope this helps.

[neo75903]

ic like a mosaic.
I thought it would swith between the cameras with intervals of x seconds.

[echooff]

We have a panasonic time laspe video cassette recorder model ag6040 at my place of employment. We have it set up to record from 10 different cameras around the perimeter of the building. Live action feeds; 3 seconds per feed. It uses a regular vhs tape we buy from walmart. It is supposed to record for 24 hours but we actually get a little over 25 hours if we let it go(it is changed at a set time every day.) It is extremely low res and painful (for me) to watch.

[Fantasma]

Just for you to know, this device http://www.smarthome.com/77304.html does the same thing, but with an internal multiplexer:

Hard disk can be upgrade, but the guarantee is voided. The Operative System used is Linux