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New Enhanced Messenger Digital Transmitter (MDT)
- High-Security Surveillance Applications
- Mobile and Portable AV Applications
- Robust Link Performance with C-OFDM
- Secure – Optional Fixed Key Scrambling or AES
- Output Frequency: 1 to 6 GHz (In-Bands)
- Low System Latency (~40 mS)
- Built-in MPEG-2 Encoder
- High-Speed Data Transmission Option
- Companion C-OFDM Receiver with Post-Detect Diversity reception
The New Enhanced, Messenger Digital Link (MDL) includes the Messenger Digital Transmitter (MDT), Messenger Digital Receiver (MDR) and one or two external Down-Converters. The MDL also provides a unique combination of security and link reliability for the most demanding short or long distance Audio/Video (A/V) point to point transmission applications. Additional Messenger features include Mic and Line-level Audio, S-Video, local set-up and power level control (MDT), Audio/Video (A/V) level control, 16 set-up storage registers (MDT), and USB-1 control (MDT).
MDL uses a robust digital modulation system known as Coded orthogonal frequency Division Multiplexed (COFDM) that provides frequency diversity and powerful Forward Error Correction (FEC) algorithms. The Messenger Digital Receiver (MDR) includes an option for Spatial Post-Detect Diversity Combining to combat short delay spread multipath reflections found in indoor environments. The MDL provides a robust wireless link that is effective against the multipath interference experienced by analog systems, and provides crisp, clear pictures in the most difficult of terrains.
The MDT accepts a composite or an S-video signal, analog stereo audio inputs (Mic or Line level) and a RS232 data input. The video is compressed according to MPEG-2 specifications. However, unlike other MPEG-2 system all of the high-frequency video signal components are preserved. The audio is converted to a 728kb/s stream.
The audio, video and data packet streams are multiplexed with basic service data to indicate the service name. The stream can be scrambled with either a simple fixed-key scrambling or AES scrambling system to provide protection in sensitive applications.
One of the biggest problems encountered in the transition from an analog to a digital A/V platform has been the inherent digital coding delays that in some digital systems are 400ms or more. The MDT/MDR combination employs a specially designed ‘low delay’ coding technology, which provides an end to end latency of approximately 40ms without the introduction of any further MPEG encoding artifacts. This ensures that the picture you see is what is happening now - crucial for applications such as sports coverage, surveillance, and law enforcement, where personnel are reacting to real-time events.
MDT Special Features
Monochrome Video Mode
Surveillance applications often do not require chrominance data in the video. The MDT has been provided with a luminance (monochrome) only mode. When in this mode bit rate is saved giving shaper monochrome pictures.
Video Only Mode
In applications where audio or data are not required, then the audio and data channels can automatically be switched off. Bit rate is automatically switched over to the video channel in this situation.
High-Speed Data Transmission Option
Using special firmware, the MDL system can be used for high-speed serial synchronous data transmission. In this mode all audio and video processing is turned-off and TTL data is transmitted using a simple data/clock interface.