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Author Topic: true mjpg video stream, or sequence of jpg images?  (Read 6496 times)

acellier

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true mjpg video stream, or sequence of jpg images?
« on: September 14, 2011, 01:44:20 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-930L 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   actual fps ~0.2  drops connection
 5 fps  ~350-1075 kbps  initially went to ~3fps, then dropped to vary 1 to 2 fps
 7 fps  ~600-1600 kbps    initially went to ~3fps, then dropped to vary 1 to 3 fps
15 fps  ~68 kbps  actual fps ~0.2  drops connection
    My DCS-930L is not stable enough to perform these tests! mydlink drops connection repeatedly, saying "Timed out" ??? or "check internet settings" ... grrr ...    sigh ...       product failure ...
    I was trying to establish that the DCS-930L, unlike the DCS-932L, MAY be implementing 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 21, 2011, 03:50:03 PM »

    I have received and set up a replacement DCS-930L. So far, so good. This camera appears to perform similarly to the DCS-932L, with reasonable short ping times and frame rates in mydlink that appear to track the user settings (which the first unit did NOT). But today's weather is cool, low 70s.
    I was able to perform the earlier aborted experiment on this DCS-930L 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): [the first column is the setting of Video SetUp]
  1 fps    ~600 kbps
  5 fps  ~1900 kbps
  7 fps  ~2500 kbps
15 fps  ~5000 kbps
20 fps ~5200bps  actually ~15 fps
AUTO  ~4900 fps actually ~15 fps
    I conclude that the camera transmits a sequence of jpg images, not true mjpg.
    Opening Live Video in a browser on the computer while viewing the fps on the iPad2 does not reveal any substantial change to the fps.
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acellier

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Re: true mjpg video stream, or sequence of jpg images?
« Reply #2 on: September 28, 2011, 04:42:06 PM »

Some more measurements of the mydlink app's reported data stream rate -
DCS-930L and DCS-932L (day mode) essentially the same -
A fairly static scene, video set to  640x480, 5 fps, java, varying the quality setting -
very low  ~1200 kbps
low  ~1550 kbps
medium  ~1600 kbps
high  ~2000 kbps
very high  ~2000 kbps
setting audio OFF decreases all of these numbers by about 300 kbps (in the camera control panel, NOT in the mydlink live view sceen, that is just a local mute).

« Last Edit: September 28, 2011, 04:51:28 PM by acellier »
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JavaLawyer

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Re: true mjpg video stream, or sequence of jpg images?
« Reply #3 on: October 02, 2011, 10:04:53 AM »

...setting audio OFF decreases all of these numbers by about 300 kbps (in the camera control panel, NOT in the mydlink live view sceen, that is just a local mute).

Are you referring to a mute control on mydlink.com? I haven't seen any control on either IE or FF.
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acellier

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Re: true mjpg video stream, or sequence of jpg images?
« Reply #4 on: October 02, 2011, 12:28:03 PM »

Are you referring to a mute control on mydlink.com? I haven't seen any control on either IE or FF.

mydlink app on iPad2 ...
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JavaLawyer

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Re: true mjpg video stream, or sequence of jpg images?
« Reply #5 on: October 02, 2011, 12:31:23 PM »

mydlink app on iPad2 ...

Odd that there's a mute button for the iPad, no mute button for the mydlink website, and no audio at all for Android ???
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Find answers here: D-Link ShareCenter FAQ I D-Link Network Camera FAQ
There's no such thing as too many backups FFC