Features

Description

Model 2416 is a streaming video server.  It converts analog video into digital data, compresses it into MPEG formats and then transmits it over an Ethernet using the UDP or RTP protocol. It is made from Sensoray’s 516 MPEG-2 frame grabber, 301-6 CPU and 207 power supply.  The 2416 has options to record video clips that may be played back locally on the 2416 or sent over the Ethernet for remote viewing. More sophisticated versions can process four video streams simultaneously and transmit them over a wireless Ethernet.  Since the 2416 is bi-directional, it can accept an Ethernet stream from another 2416 and convert the encoded digital video into composite video outputs.

Audio Frame Grabber

Model 2416 has two audio input channels that are synchronized to the MPEG data.

Decoding Latency

Although it is possible to use 2416 hardware to decode MPEG data, this process does not have low latency compared to Sensoray’s Display & Control software.  2416 hardware latency is 5 seconds, while our software player’s latency is less than one second.

Display and Control Software

Sensoray's real-time Display and Control Software decodes and displays up to fifteen MPEG1 and/or MPEG2 streams with a low latency of 1/2 to one second.  Thumbnail images from remote video servers may be positioned over a background such as a map or building plan.  Multiple server images may be selected for expansion to full size and full frame rate.

Software and Manuals

2416 Instruction Manual |  10/10/05

Digital Video Recorder

Video clips may be stored on 2416 servers that have internal storage media as described in this section. The movies may be replayed from local or from remote 2416’s or they may be rapidly downloaded to remote clients.  For example, the daily movies accumulated in a vehicle’s DVR may be rapidly transferred over an 802.3 wired Ethernet.

Movies can be stored on a removable compact flash card.  In the local record mode, MPEG data from the frame grabbers is recorded to storage media. Proper care is taken to prevent significant data loss in the event of a power loss.  While data is being recorded it is also available as composite video from the frame grabbers

Ethernet Protocols

The UDP format (user datagram protocol) offers the fastest data rates and minimum CPU usage at the expense of minimal error checking.  The 2416-4 can uni-cast four MPEG2 data streams at full frame rates when using this protocol.

A disadvantage of the UDP format is that it cannot be played using popular stream players such as QuickTime. However, the latency
 i.e., the time delay between recording and displaying, while using these players, can be several seconds.

The RTP format (real time protocol) trades off CPU and memory usage for error correction and compatibility with QuickTime and Real Player. Sensoray sells a multi-stream, low-latency software RTP player for Windows 2000 and XP. The latency of Sensoray's software player can be as low as one half second when processed on a 2 GHz, Pentium-4 system. A disadvantage of RTP is that it uses twenty-five percent of the 2416’s CPU time, while UDP uses less than five percent. Hence, the 2416 can only support two RTP streams.

Video Storage

There are three storage options. Video clips may be stored on a 2.5 inch IDE hard drive by adding the 300TA interface board and IDE cable. IDE mechanical hard drives have limited temperature and vibration specifications, hence, they are not recommended for use in vehicles or outdoors environments. Some 2.5-inch hard drives may draw too much power from the 2416's power supply and must be powered by an auxiliary power source. Mechanical IDE hard drives have the advantage of low cost and high density.
 

Once MPEG video data is stored on the 2416 it may be decoded and viewed by using the 2416’s hardware decoding and composite video output channel.

Recorded movies can also be sent over the Ethernet for remote viewing with QuickTime or Real Player. In this case, the 2416 sends MPEG data which the software player must decode.

Camera Control

The 2416's CPU sends pan, tilt and zoom command from the Ethernet to one of the RS-232 ports. Many cameras use serial ports for position control. PZT software is included for popular camera assemblies such as Sony (Visca), Pelco(D protocol) and Cohu (iDome).

To facilitate camera adjustment the digitized video can be looped back to the composite video output for viewing on a TV monitor. This is the default mode for the video output.

Bit Rates and Bandwidth

The data rates discussed below refer to the bit rate from the MPEG frame grabber used by the 2416. The rates do not refer to Ethernet bit rates, which are fixed at 10 Mbits/sec or 100 Mbits/sec. The 2416's programmable bit rate allows trading image quality for bandwidth.

Higher bit rates from our MPEG frame grabber give better quality images than lower rates.  Full-size interlaced images of 30 frames/sec will start to show distortions below 1 Mbits/sec, however, image quality improves only slightly above this rate.

When low bit rates are selected e.g., 100 kbits/sec, the amount of distortion depends on the amount of motion in the scene.  A chess game will have less distortion than a soccer game.

A variable bit rate may also be selected.  This mode tries to maintain good image quality by varying the frame grabber bit rate according to the amount of motion in the scene.

It is also possible to decrease the bandwidth by decreasing the image size.  Selecting CIF size images of 320 x 240 pixels will reduce the required bit rate by four compared to 640 x 480 pixel images that occur at the same frame rate.

If there is not much motion in a scene, a lower frame rate may be selected to reduce the frame grabber's bit rate. Lower frame rates will show motion artifacts from fast-moving objects. Even though such as stream can be recorded at a lower frame rate, most MPEG viewing programs will play the stream at 30 frames/sec for NTSC and 25 frames/sec for PAL. The stream will be playing in a fast-forward mode. For example, a 15-frame/sec recording will be displayed at twice the normal frame rate.

Embedded Linux

The board set is supplied with specially configured Linux for high reliability and fast response. After power is applied, the software is automatically loaded to RAM from flash memory. The 2416 will then stream MPEG data to the Ethernet port.

Sensoray has optimized Linux installation for the 301-6 CPU. Although it is possible to recompile the Linux kernel, Sensoray does not offer technical support for this operation.

Mechanical Drawings and Images
Figure 1. Simple Application
Figure 2. Encoding and Decoding
Figure 3. 2416 Sequential camera selection using one frame grabber
Figure 4. Destination of composite video output from DVR
Figure 5. Sources of composite video output from DVR
Figure 6. Destination of recorded video to remote stream player

Enclosure Options
2416 Stack
2416 with standard enclosure
2416 with weatherproof enclosure

2416 General Specifications

Software supplied        Linux 2.4.10 kernel  | Linux driver for 512 frame grabber |  Linux network API

Video input                    725 x 500 PAL  | 640 x 480 NTSC

MPEG type                    30 f/s MPEG1,2 elementary stream

Ethernet                        10/100 base-T

Protocols                        Ethernet UDP, RTP

Serial ports                    Two RS-232

Watchdog timer            1.6s time-out, open collector

Memory                          16 MB flash, 16 MB SDRAM

CPU                                Sensoray Model 301-6

Power supply                Sensoray Model 207-01, Model 207-02 with 340-11b/2

PC I/O board                  Model 300TA - Optional PC I/O board for IDE drives

Input power                   4.5 watts, 12 to 35 VDC without wireless |  16 watts, 24 VDC with 340-11b/2 wireless