Active Video Node - Digital CCTV, Digital Security, IP Video, Remote Surveillance

1. INTRODUCTION

1.1 Purpose And Scope
This document provides a short technical introduction to the Active Video Node outlining its main hardware features together with the broad project aims. The software architecture is not included in his document, since this is application specific.

2. SUMMARY SECTION

2.1 Introduction
The Active video node is a standalone computer board based on the Philips Trimedia processor. It will digitise standard analogue video and or audio information from up to four different sources and direct the output via TCP/IP or RS232 interface as serial data streams.
Local memory storage comprises 16mbytes of SDRAM and 8mbytes of Flash non-volatile memory. This is used for either programme storage or recording of a small number of video frames.

There is also support for the PCI bus which allows the unit to be plugged into a standard computer for debugging and testing purposes. This mode requires that the computer case is not fitted, since the footprint of the card exceeds the PCI physical dimensions.

The main processing element is the Philips Trimedia graphics processor. This will execute programmes in either "native" mode directly from memory without the support of a standard operating system, or under the control of a standard real-time operating system known as "pSos". The key feature of the Trimedia processor against a dedicated graphics accelerator chip is that it is software programmable. Thus according to operational requirements the unit may be dynamically reconfigured to provide JPEG; MPEG-2; or H.263 video compression formats, and indeed any other available libraries. The unit may therefore be remotely maintained and upgraded by use of local or wide area network or public telephone network.

A major design goal of the project was to ensure that the card production would remain "low cost", whilst providing sufficient processor power to handle near real-time compression at resolutions suitable for the security market. Central to this aim was the selection of the processor. Various alternative designs were considered such as the National Semi-conductors Geode device and the "Strong Arm" processor from Intel. The Trimedia device was selected as the best available candidate. Its intended market is for use in digital video set-top boxes and other high volume applications and therefore it has been priced very competitively also requiring a relatively small amount of support logic. It is also backed by Philips semi-conductors and has the necessary guarantees for continuity of supply that long lifetime projects in the security market require.
A further design goal was to ensure operation in normal office conditions without the use of forced cooling or large size heat-sinks. This is essential if the unit is to be integrated into existing equipment or for use in long term unattended applications. In addition the power supply system caters for self-reset under software programmable conditions or remote reboot for remote firmware upgrade and reboot operations.

Figure 1:Active Video Node
Active Video Node

Figure 2: Active Video Node (close)

2.2 Hardware features

General:
	Low cost video/audio digitising node with TCP/IP or serial output video stream TriMedia processor dynamically re-configurable to support alternative compression technologies
Power:
	Standalone 12v dc operation Operation without additional heat-sink or fan in office environment Self resetting or remote reset for remote reboot operation
Size:
	175mmx140mm
Control I/O interface:
	2 Output control lines 4 Alarm trigger inputs, input over-voltage protected PCI interface to computer (for debugging and PC acceleration mode)
Analogue interface:
	4 Switchable video inputs via BNC connectors 1 audio input via standard Din connecter
Digital I/O interface:
	Serial RS232 x1 Serial RS485 x1 10/100 RJ45 TCP/IP connection
Operating systems:
	Native mode PSos real-time operating system
Onboard Memory:
	16mbytes onboard SDRAM arranged as 4mbytesx32 4Mbytes Flash Memory

3. MAIN SECTION

3.1 Tri-media processor
TM1300 is a media processor for high-performance multimedia applications that deal with high-quality video and audio. These applications can range from low-cost, dedicated systems such as video phones, video editing, digital television, security systems or set-top boxes to re-programmable, multi-purpose plug-in cards for personal computers. Popular multimedia standards such as JPEG; MPEG-2 and H.263 are available as libraries, but its orientation around a powerful general-purpose CPU makes it capable of implementing a variety of multimedia algorithms.

Apart from its role as a graphics processor the parallel architecture enables the device to operate as a general purpose processor capable of running "C" compiled programmes in addition to its graphics requirements. Thus modem control and I/O handling can be managed without the need for added co-processor or glue logic hardware.

3.2 Video Input Interface
The video input is based around the Philips SAA7113H 9bit high quality digital video decoder. The device has an integral 4:1 multiplexer which allows for up to four separate video sources, each pair of inputs can be reallocated to handle a separate Y/C source if required.
For high performance installations there would be one AVN (Active Video Node) serving each camera and therefore the input multiplexer is essentially redundant.

The four video signals are derived from 75 ohm BNC connectors to accept standard 1V video signals (PAL or NTSC) and are 75 ohm terminated via 47u AC coupling capacitor to allow for powered coax installations.

The SAA7113H is fully configurable from the TriMedia processor via the I2C bus. The chip integrates a digital PLL for line locking and automatic multi-standard detection. Internally the chip uses 9bit precision and outputs Standard ITU 656 YUV 4 :2 :2 format (8-bit) on its VPO output bus – the required standard for direct insertion into the TriMedia video input processor.

3.3 Audio I/O Interface
Audio I/O is handled by the Philips UDA1344TS which is a high quality single-chip stereo Analog-to-Digital Converter (ADC) and Digital-to-Analog Converter (DAC). The audio uses standard 2V levels brought out to a standard 5-way Audio DIN. The I/O channels are AC coupled. An external Power Amp would be required for intruder challenging.

3.4 Local Memory
The TriMedia implements a glueless 32-bit wide SDRAM interface allowing very high performance 133MHz burst mode transfers ideal for image manipulation.

3.4.1 Flash Memory
The card incorporates 4Mbytes of 8bit wide Flash memory (non volatile memory) primarily for program storage. The Flash memory may also find use for video archiving after power failure. The board design could accommodate 8Mbytes without design changes and up to 16Mbytes with design changes. Therefore if it is thought a likely requirement some design changes should be made now in order to avoid backward compatibility problems.

3.4.2 SDRAM
The TriMedia can accommodate various SDRAM sizes and configurations but the single option adopted is for two 16bit wide SDRAM devices of the 64Mbit generation, each contributing 8Mbytes to a total 16Mbytes. Future SDRAM generations would allow fairly simple upgrading of the design to higher capacity in a subsequent revision if required.

3.5 Power Supply
The card has an integral high efficiency switch-mode power supply with in-line self resetting fuse and reverse polarity protection diode. The power supply outputs 3.3V and 2.5V and is optimised for 12V input, but with fuse suitably adjusted could accept down to 6V or up to 15V at least. (There is currently a small linear 5V regulator which is expected to be designed out ultimately, allowing the card to accept 5V input)
At 12V the current consumption is 500mA (typical) to 660mA (max).

3.6 PCI interface
The inclusion of a PCI interface is primarily to provide a simple means of testing and programme download for the card. Therefore it was not a design aim to adopt the standard PCI card size format. However by re-layout of the artwork, it is envisaged that the card could be used as a graphics co-processor for incorporation into a standard PC product to provide acceleration and multi-processing capabilities.
The board is compatible with the electrical requirements of the PCI bus specification revision 2.1.

3.7 Interface Circuitry

3.7.1 RS232 Interface
This interface is intended for high speed data communications such as video and audio data streaming across ISDNII connections and provides an alternative transmission to TCP/IP where applicable. It is envisaged that this will interface with a modem or ISDNII module

3.7.2 RS484 Interface:
The primary use for this interface is for control requirements such as pan tilt zoom camera control and interface to the variety of peripheral devices which use RS485 protocol, eg matrix switchers etc. However it may also be configured as a second RS232 port if required.

3.7.3 TCP/IP
The TCP/IP interface is based on the Intel 82559 10/100 ethernet controller which requires virtually no additional support logic. The TCP/IP stack itself runs on the Trimedia device and is available as a compatible purchasable library component.

3.8 Block diagram
The following diagram shows the interconnection of the main functional elements of the board. Dotted lines indicate product variants:

Block diagram

4. TESTING FACILITIES

4.1 JTAG Interface
The Trimedia device supports JTAG interface. Through suitable JTAG interface boards testing and debug may be carried out via a standard PC.

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