Frame Rate

 

MOBOTIX cameras do not generate an analog live image, they generate ready-edited and compressed digital images with zoom and pan. In contrast to classical systems, there is no difference, in principle, between the maximum live frame rate and the maximum storage frame rate. In the current software release in MOBOTIX cameras the frame rate in MxPEG mode with good quality images is 50 percent of JPEG (see image compression):

• 25 frames per second in CIF format (320 x 240 pixels), approx. 1.2 Mbit/s
• 11 frames per second in VGA format (640 x 480 pixels), approx. 1.4 Mbit/s
• 3 frames per second in megapixel format (1280 x 960 pixels), approx. 1.2 Mbit/s

Live images can be displayed and shots saved at the same time at these image and data rates. The frame rate is not dependent upon the system, it is only limited by the computing performance of the integrated camera computer.

Storage Frame Rate in the Case of Multiple Cameras

Anyone comparing frame rates should also consider the frame rate of the saved video streams from ALL the cameras. In a MOBOTIX system around 30 cameras can record at full frame rate (25 fps CIF) to a single standard PC (Pentium IV, 2.8 GHz). The data rate in CIF format is around 1.5 Mbits per second including audio. With this number of cameras

The major strength of the MOBOTIX camera is that it also supports the transmission or saving of different video streams at different frame rates. Lip-synchronous audio is contained in each channel. In parallel to a live transmission at 25 fps, the storage frame rate can be lowered to 6 fps, for example, for reasons of efficiency. Rival systems cannot do this.

Video and JPEG Single Frame Simultaneously

Anyone who wishes to work exclusively via the web browser, i.e. without plugins or without ActiveX, generally has to put up with a reduced frame rate, unless they use the streaming mode in the Netscape browser and the camera supports this mode. This is the case in MOBOTIX systems. Quicker (smoother) frame rates can generally be achieved with special programs which are installed on the PC than with the browser, albeit at the expense of universality and simple access to the camera images from anywhere. MOBOTIX supports both simultaneously: streaming with audio and JPEG via a browser.

Image Format Adaptation Saves Storage Space

In addition, MOBOTIX cameras support the free choice of image formatting, cropping and zoom level. This means that the user can transfer, display and save only those particular areas which are of relevance. Depending on the image resolution, the frame rates are then reduced by interpolation of the above table.

Note: It should be noted that the higher the frame rate, the greater the volume of data and, thus, the bandwidth required for the transmission. In order to reduce the data load with multiple users, they can set their frame rate individually; this means that while one user retrieves images at a rate of 25 fps via the LAN (Local Area Network), a second views the images over the Internet at a rate of 2 fps. The images can be saved in parallel at a third frame rate (1 - 25 fps). The audio channel is transmitted lip-synchronously to all users irrespective of the frame rate.