<p>Based on neuhaus' comment, I've confirmed that the Foscam uses MJPEG compression.  Thus it's clear how a brighter (hence more detailed) scene would generate higher bit rates by repeatedly sending complete full frames.  I thought that it would be smarter than that.</p>

CC BY-SA 3.0
2015-03-20T23:07:02.980Z
2015-03-20T23:07:02.980Z
Paul Uszak
<p>Our eyes and brains are more sensitive to data in the bright areas so compression schemes generally throw out more of the data in the dark areas. If the video is mostly dark, then it compresses very well because they can throw out more data and you don't notice. But when it's bright (assuming it's not overexposed), less data can be crunched down without you noticing it.</p>

CC BY-SA 3.0
2015-03-19T14:25:36.140Z
Thanks for that, but I draw your attention to the 2nd paragraph.  I thought that a static image would generate much lower (virtually nothing) network traffic as nothing is changing between frames..?  Does video imaging not work this way?
Paul Uszak
CC BY-SA 3.0
2015-03-19T14:40:01.953Z
It depends on the compression used. MJPEG compresses each frame individually for example.
neuhaus
CC BY-SA 3.0
2015-03-18T03:24:29.857Z
2015-03-18T03:24:29.857Z
user1118321
<p>I've been watching the feed from a webcam (Foscam 8910).  When the scene is bright (lit with sunshine) the video feed is approx. 350 kBytes/sec.  When I view the same scene lit very dully with just a dim bulb, the feed comes at approx. 50 kBytes/sec.</p>

<p>As I understand it, the video feed only transmits the changes between frames.  Once the image has been transmitting for a few seconds, and there is no change whatsoever in the scene, the feed should settle down.  </p>

<p>Why is there a seven fold difference in network traffic between light and dark scenes?  Shouldn't they be identical?</p>

<video>
Why does a bright video feed send more data than a dark one?
Paul Uszak
# Why does a bright video feed send more data than a dark one?

(Asked by: username_0 on 2015-03-18)

I've been watching the feed from a webcam (Foscam 8910). When the scene is bright (lit with sunshine) the video feed is approx. 350 kBytes/sec. When I view the same scene lit very dully with just a dim bulb, the feed comes at approx. 50 kBytes/sec.

As I understand it, the video feed only transmits the changes between frames. Once the image has been transmitting for a few seconds, and there is no change whatsoever in the scene, the feed should settle down.

Why is there a seven fold difference in network traffic between light and dark scenes? Shouldn't they be identical?

**Tags:** video


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## 2 answers

### Answer by username_0 on 2015-03-20. Score: 1 | Accepted answer

Based on username_2' comment, I've confirmed that the Foscam uses MJPEG compression. Thus it's clear how a brighter (hence more detailed) scene would generate higher bit rates by repeatedly sending complete full frames. I thought that it would be smarter than that.


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### Answer by username_1 on 2015-03-18. Score: 1

Our eyes and brains are more sensitive to data in the bright areas so compression schemes generally throw out more of the data in the dark areas. If the video is mostly dark, then it compresses very well because they can throw out more data and you don't notice. But when it's bright (assuming it's not overexposed), less data can be crunched down without you noticing it.

> **Comments:**
> **username_0**: Thanks for that, but I draw your attention to the 2nd paragraph.  I thought that a static image would generate much lower (virtually nothing) network traffic as nothing is changing between frames..?  Does video imaging not work this way?  
> **username_2**: It depends on the compression used. MJPEG compresses each frame individually for example.  

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