Overview

Most digital security cameras are limited to encoding one format at a time:

1. JPEG
2. MJPEG
3. MPEG-1
4. MPEG-4
5. Wavelet
6. Proprietary derivative of one of the above standards.

This means whatever the comsearchion scheme is used to develop the real time motion video is the same used for archival purposes. We all know that when the "one-size-fits-all" approach is employed, nobody gets the perfect "fit". There are some schemes being employed, primarily using wavelet comsearchion, that allow one type of stream to be streamed in multiple resolutions. However, we have found this technology does not meet most price/performance requirements.

Additionally, we reviewed both hardware and software encoding schemes which have yet to be certified as an IEEE standard. We only considered "standard" encoding schemes because we want to employ an open architecture.

WatchCam™ IP smart cameras and MultiWatch™ encoder cards can encode three formats simultaneously. In the factory default, one of the three formats provides JPEG still images. The other two provide streams of MPEG video.

JPEG encoding

Encoding surveillance video into archival quality motion video can be very space intensive. One of the best options is to encode the video into high quality JPEG images (704 x 480 pixels). When coupled with motion detection (Activity Gated Storage™ ), the required archive space for JPEG images can be significantly less than that required by MPEG streams. The factory default frame rate is set to archive 1 JPEG image every 2 seconds. The frame rate may be adjusted, by the user, from as fast as 3 frames per second to as slow as 1 frame per 10 seconds. Using the factory default, the average size of the JPEG is 30-45kb. This resolution can be increased or decreased by changing the comsearchion ratio (Quality Level), defaulted at 10:1.

MPEG encoding

Motion video streams are used for two purposes:

1. Monitor the premises, in real time, to maintain situational awareness.

2. Archive for later use in event reconstruction.

We provide the MPEG stream at two bit rates. The higher bit rate is used in situations when a large, high resolution image is required. This stream can only be transported over an infrastructure designed to handle large amounts of data. Generally this would be limited to LAN/WAN use. The lower bit rate is used when the situation requires many simultaneous streams to be displayed or when the infrastructure has limited bandwidth, such as internet access.

• SIF MPEG-1 @ 352 x 240 pixels, 30 fps, 1Mbps: This real time, motion video stream offers good resolution on a 17" monitor in a window pane approximately 5" x 3.5" and medium resolution in a pane approximately 11.5" x 8".

• QSIF MPEG-1 @ 176 x 112 pixels, 30fps, 128kbps: This real-time, motion video stream offers fair resolution on a 17" monitor in a window pane approximately 3.5" x 2.5" and medium resolution in a pane approximately 2.5" x 1.75".

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