A: We use a proprietary method compression
algorithm. The algorithm consists of two phases:
- First phase: calculation of inter-frame differences.
The algorithm divides each frame by 8x8 pixel blocks. The average
brightness level is calculated in every such block. The algorithm
takes each pair of frames within the incoming sequence. It then
performs a comparison of the blocks in the same positions within
these frames. If the differences in brightness level rise above
the threshold.defined in configuration (Delta sensitivity) this
block will be marked as changed and
consequentially will have to be recorded.
- Second phase: compression of changed blocks
Marked blocks form the sequence. The sequence is compressed by
algorithm based on DCT (Discrete Cosines Transform). The quality
of compression is adjustable in the configuration (Picture quality).
The compressed section goes to the video database as a single
record to be recorded on to the hard drive. A key frame (complete
frame) is recorded additionally for every defined period of time
to ensure accuracy of video information and to avoid accumulation
errors. This proprietary method gives better picture quality/storage
size ratio compared to the standard compression algorithms (i.e.
MPEG, MJPEG, H.262, etc), especially when the recording of small
details is required. This is an important factor for digital surveillance
systems.
