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10 Commandments of Proper Cable Termination
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| C7 in CA |
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Posts: 714
Joined: 21 Nov 2004
Location: Nor*Cal
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Posted: Mon Aug 25, 2008 6:17 pm
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| Jim Barrett wrote: |
| So, don't most compression formats register & record the initial image & then achive compression by recrding only when that image changes? |
Good Question.
When I am recording continuous I can watch the hard drive space dwindle even while there is no motion detected by the DVR. So I hope it is recording whole new images. That's my whole point of recording continuous. I am trying to catch stuff that the DVR may not detect as motion.
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Scott
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| Thomas |
Moderator
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Posts: 2102
Joined: 17 May 2004
Location: Houston, TX
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Posted: Mon Aug 25, 2008 9:31 pm
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| Jim Barrett wrote: |
| So, don't most compression formats register & record the initial image & then achive compression by recrding only when that image changes? I thought I understood that that was the way it worked (correct me if I'm wrong). If that is the case it seems the memory involved in recording that blank picture would be pretty small |
Yes and no. MPEG-2/4 and related codecs will all record that way. MJPEG based codecs do not. Which makes it sound like MPEG type codecs will produce smaller file sizes, right?
Sometimes. At low frame rates the number keyframes as a percentage of the total stream is going to be higher. Keyframes for MPEG based codecs are almost always larger then the same quality MJPEG frame. And MJPEG handles gray in a much, much better fashion. So low framerate combined with nighttime can create situations in MPEG related codecs suck. Gee, I wonder where one might find those situations in CCTV?
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Thomas
Sales Support
Video Insight
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| MRakes |
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Posts: 15
Joined: 14 Jul 2008
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Posted: Tue Aug 26, 2008 11:17 am
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#8 is more of a analog, broadcast video thing (TV/ CATV).
That source stops producing video but since the cable is plugged in, it changes the termination. In a station's master control, this changes the "sync" enough to cause a big tear or roll when changing video sources.
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