Are You Smarter than a Security Trade Magazine?By: John Honovich, Published on Aug 25, 2011
If you have any IP video surveillance skills, you should easily spot at least 1 of 2 fundamental errors from a single page 'test report' published by GIT security magazine and VMS manufacturer Seetec's 'Hardware Competency Center'.
Here is the key excerpt from a test of the Axis M1104:
"On average, the frame rate was approx. 1.6 MB/s. A frame rate of 3.31 MB/s was achieved as a temporary maximum."
Did you spot the errors?
- Confusing frame rate and bit rate: Frame rates are measured in frames per second (e.g. fps) while bit rate is measured in bits per second (e.g. bps). This should be easy to spot for even a novice.
- Confusing bits with bytes: The measurement is in Bytes (denoted by a capital B). Since 8 bits is equal to a byte, the statement implies that the average bit rate is 12.8 Mb/s - way too high for a 720p H.264 camera. (We've tested the Axis M11 series and the average for 30fps/720p is roughly 1.6 Mb/s - note small b for bits). This is a little more advanced but should be easy to find for any mid level technician / engineer.
If you know the answer to this question, you likely have an advanced knowledge of Axis IP cameras and IP cameras in general:
Question: Why would the frame rate of the Axis M1104 drop at lower light levels?
The answer is that Axis, by default, typically sets the maximum exposure speed to 1/6s. When lighting is insufficient, Axis slows the exposure simultaneously decreasing the frame rate. This makes the imager brighter than keeping the exposure at 1/30s for a full 30fps image. However, it silently drops your frame rate by 80%.
Take a look at how this happens in our 7 camera office shootout including multiple Axis cameras and contrast to the performance of rival manufacturers.
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