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Old Feb 04, 2012, 04:26 PM
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Originally Posted by heribert808 View Post
Video data rate 10Mbps.
I would like to test the high video quality. I have set up the configuration to 10Mbps, but the
Gspot shows only 7Mbps (bps=7136). My two #11 show more than 10Mbps
(sometimes (bps=11345).

#16 Config

Date time=[2012/02/04-19:35:51];date time setting,format yyyy/mm/dd hh:mm:ss,
Movie resolution=[0];Movie resolution setting,0:720p 30fps,1:wvga 30fps,2:vga 30fps,
Movie cycle time=[1];movie cycle time,0:5 minutes,1:20 minutes,2:40 minutes,3: 70 minutes,
movie Loop Recording=[0];set loop recording on or off,0ff,1n,
Movie stamp=[1];set date / time stamp on or off,0ff,1n,
Movie sound=[2];set movie sound,0:mute,1:level 1,2:level 2,3:level 3,
LED=[1];set LED flicker when recording,0ff,1n,
Movie quality=[0];set movie quality,set movie data rate,0:10 Mbps,1:7 Mbps,
Power off=[1];set system auto power off time when system pending,0ff,1:30 seconds,2:1 minutes,3:2 minutes,
{MicroDVR mov 2012/01/17 v0.18}

does v0.18 support 10Mbps ?
Yes it does, but the h.264 video compression algorithm uses a variable data rate which it alone decides how high that needs to be based on the complexity of detail and the amount of motion in the scene. I can't say with 100% certainty, but I believe the data rate you set in the config only sets the approximate average data rate. So if the scene detail can be recorded with equal quality at lower data rate as determined by the h.264 codec, it will do so. And it will sometimes average a higher data rate than the set value by as much as 50% or so! There also seems to be a minimum average data rate built in so the average never goes below about 7Mbps with either of the settings.

If you check the histogram for a typical video you can see a visual graph or table of data rate ranges used during the course of your video. I use the AviDemux editor built in histogram function for this... see the attached screen shot for a clip I shot yesterday with 7Mbps rate in bright sun with lots of detail and constant motion with my cap mounted camera. You can see the data rate spiked up to well over 25Mbps in small portions of the video, and the average data rate was actually was over 11Mbps, even with the camera toggled for 7Mbps data rate!

So, if you want to tax the 10Mbps setting to it's limit, shoot HIGHLY detailed scenes in bright light with lots of contrast and constant motion... it doesn't have to be fast panning. I've said here and in the #11 thread several times, I don't think you will see ANY noticeable difference in the video quality at that high setting, because the lens does not have enough resolving power to record the fine detail that the higher data rate MIGHT capture better. You're just adding a higher allowable data rate to defining a pixel that was a little blurry to begin with, or to define a scene that will looks just as good to your eye while playing at a slightly lower data rate!

If you shoot side-by-side videos with identical #16 cameras at the two data rate settings and did static frame-by-frame comparisons, you MIGHT see a few frames with portions that look a little better, but stepping to the next frame those differences can disappear and even look better in the other camera video, simply due to the way the codec handles the P-frame compression between I ( key) frames. And when those frames are all streaming past at 30 fps, your eye cannot discern any difference... at least my eye can't
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Last edited by Tom Frank; Mar 25, 2012 at 11:19 AM.
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