DVR multiple streams

[genealle 0]

Got a pretty basic question I think:

 

Do multi-channel DVR's record multiple streams of video, or just one that is multiplexed?

 

Such as, does a 4 channel DVR record 4 channels of video, so you can look at just a single, full size image during playback?

 

Thanks!

[kaysadeya 0]

The answer to the last part of your question is yes. Others here have much more knowledge than I do on this topic, but I believe most or all DVRs record each input channel to a separate file on the disk

 

Very cool stuff. Once you've used a multi-chanel DVR, there's no going back to a VCR.

Edited February 19, 2005 by Guest

[rory 0]

As far as I know its still multiplexed, but this also depends on the DVR and the way in which it records, PC OS or RTOS, etc.

 

Multiplexed is just switching between each camera very fast. Possibly the reason PC based can get more real time is due to the processing Speeds of a PC OS compared to the much slower RTOS processors.

 

Rory

[genealle 0]

While poking around for a design checklist, I found a link to the page below. Original link posted by avonconsulting:

( http://www.digitalvideorecorder.net/articles.htm )

 

http://www.digitalvideorecorder.net/article17.htm

 

"Many of the same features offered by multiplexed DVRs can be found in

multichannel units. However, there are some notable differences between

the two.

 

First, multichannel recorders allow all 60 images per camera to be

recorded, whereas, in a multiplexed unit, video inputs are divided

between the 60 images. This division, or time-sharing of images, is

what causes the jerky motion during playback (this occurs when the image

rate per camera falls below 15 images per second)."

 

So, does than mean that even a multiplexed DVR can play back a single camera at full screen, or only a multi-channel has that feature?

 

Thanks!

[kaysadeya 0]

Here are some links:

 

http://www.securitycameraworld.com/DVRFAQ.asp

 

http://www.telexper.com/telexper-en/faq/faq.htm

 

http://www.eyespyvideo.com/faq/multicamfaq.htm#question9

 

http://www.eyespyvideo.com/faq/cctvglossary.htm#dvr

 

http://www.eyespyvideo.com/faq/dvrfaq.htm

[cctvexpert 0]

It depends on the system. The cheaper ones record a single image that is multiplexed. The higher end units record multiple images. Beyond this is the question of unicast and multicast which is a whole other issue, more to do with remotely watching the videostreams from different feeds. But I guess you are talking record only.