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Author Topic: true mjpg video stream, or sequence of jpg images?  (Read 3600 times)

acellier

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true mjpg video stream, or sequence of jpg images?
« on: September 14, 2011, 01:44:29 PM »

    When accessing the camera on mydlink, or on a browser using http://x.x.x.x/mjpg.cgi, I would expect the net bit rate to be substantially less than for a sequence of jpg's, since true motion-jpg uses a lossy form of intraframe compression typically yielding a 20:1 data reduction (according to wikipedia). Indeed, I can readily see this reduction in mjpg clips made on my Canon S5is camera.
    It's not clear whether that is happening with the d-link DCS-932L camera (640x480, quality "high", java). The mydlink app "Info" on the iPad2 (802.11n; no other apps running; no other streams to computer) shows these data rates (basically static scene, a few leaves moving):
 1 fps  ~  605 kbps
 5 fps  ~2020 kbps
 7 fps  ~2600 kbps
15 fps  ~5100 kbps  actual fps ~14.2
20 fps  ~5200 kbps  actual fps ~14.6
Auto    ~4800 kbps  actual fps ~14.2
    Whereas, the individual jpg files that are sent by ftp are each about 45kB ~ 400kb so by simple arithmetic, it appears that the mydlink stream is simply a sequence of complete jpgs. Also that (my?) frame rate maxes out.
    I welcome some discussion on this point; mobile users might benefit from reduced traffic of true mjpg.
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acellier

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Re: true mjpg video stream, or sequence of jpg images?
« Reply #1 on: September 16, 2011, 03:14:38 PM »

Today the DCS-930L went back to D-Link for RMA replacement. I hope the replacement works correctly. Stated policy is, only if second unit is like the first, then they will replace with 932.
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JavaLawyer

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Re: true mjpg video stream, or sequence of jpg images?
« Reply #2 on: September 17, 2011, 08:03:55 AM »

Today the DCS-930L went back to D-Link for RMA replacement. I hope the replacement works correctly. Stated policy is, only if second unit is like the first, then they will replace with 932.

I presume that if the unit is upgraded (i.e. the second unit shares the same defect as the first), you would be responsible for paying the difference between the DCS-930L vs. DCS-932L price. Is this the case or do they simply ship you the newer model?
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