MIGRATING TO MPEG-4:
MOVING FORWARD WHILE LOOKING BACKWARD
By: Sean Drew, Business Development Manager,
Integrated Microwave Technologies (IMT), LLC
The Scene:
The time is 1:13 a.m. and the radio barks out ten-codes about a robbery: One man is down and the perpetrators are fleeing the scene by car. Law enforcement launches an aerial search, which moves from the edge of the city toward the outlying forest area. The chopper is equipped with the latest MPEG-4-enabled video system with infrared capabilities, transmitting a real-time aerial record of the search back to newly upgraded base receivers. The chase, however, leads the helicopter to fly over two smaller jurisdictions with police departments that have older MPEG-2 receivers, so instead of a direct, ongoing video link between all involved via a one-to-many communications scheme, the lack of interoperability between the dedicated MPEG-4 and MPEG-2 equipment adds extra steps, costing the pursuit precious time.
Where We Are Now:
With many installations both large and small embracing the standard, MPEG-4 video and audio encoding- and decoding-enabled equipment is a must-have for many law enforcement, fire, rescue and security operations. As it offers high-quality HD picture and audio, and metadata capabilities at one quarter to half the bandwidth of legacy MPEG-2 systems, MPEG-4 enables field operations to send out critical video instantly. This allows for its dissemination to multiple interested agencies without straining network bandwidth.
Additionally, at the regional level, there is an accelerating trend among law enforcement, fire, rescue and security operations departments seeking to upgrade from MPEG-2 to MPEG-4 so that they can remain interoperable with neighboring stations. While moving to MPEG-4 brings operations efficiently into the future, not everyone has made the change, requiring a system that can also look backward to include the older, industry-standard MPEG-2 equipment. The goal in the move to MPEG-4-based equipment is to maintain interoperability between both systems.
MPEG-2 Versus MPEG-4:
To meet the growing demands for the capture and dissemination of digital video and audio, the Motion Picture Engineers Group (MPEG) has produced an evolving range of data compression standards over the years. Both the MPEG-2 and MPEG-4 standards are suites made up of different parts, with Part 1 traditionally dealing with file format, Part 2, video and Part 3, audio. MPEG adopted MPEG-2 (H.262) to meet the demands of broadcast, emerging Internet and cable distribution, and the DVD format. As digital technology progressed, with it grew public demand for ever-higher quality, making it necessary to find a way to pack information into a signal more efficiently. MPEG developed MPEG-4 (now with 31 parts) to meet these demands, especially for Internet streaming, Blu-ray and the needs of portable smart devices. Today, MPEG-4 Part 10/AVC, or H.264, is arguably the most popular format for video and audio.
MPEG-4 Benefits:
There are several reasons why law enforcement departments move from MPEG-2 to MPEG-4 encoding. Foremost is that MPEG-4 allows for more efficient video and audio encoding, which reduces the data rates of HD and SD video. Reduced data rates, especially in microwave applications, allow for more robust Coded Orthogonal Frequency Division Multiplexing (COFDM) parameters. These robust COFDM parameters in turn allow for an increased operational range of radius—critical for our opening crime scenario.
Departments have also embraced the increased resolution of HD video, installing HD cameras on their platforms. MPEG-4 allows an agency to transition from SD to HD video without negatively affecting performance in distance. It also makes possible the use of narrow-band COFDM (NBCOFDM), covering bandwidths 1.25MHz and 2.5MHz, which is extremely beneficial for agencies that operate multiple aircraft within a single licensed channel. MPEG-4 also places a reduced bandwidth payload on video management networks, leading to a 30-percent decrease in payload in some cases.
Making the Change:
So what resources are necessary to complete a backwardly compatible upgrade to MPEG-4 transmitters and receivers? Upgrading the receive side of a microwave link can be had through the addition of a cost-efficient MPEG-4 decoder. The decoder will take the Asynchronous Serial Interface (ASI) output of any manufacturer’s digital receiver and output HD/SD SDI, composite video, L/R audio and IP streaming. This decoder also comes standard with BCRYPT key-derivation function coding for passwords and AES128 and 256-bit decryption.
The digital transmitter side, meanwhile, might simply require a printed circuit board (PCB) replacement that adds MPEG-4 HD/SD encoding ability while retaining existing MPEG-2 capability. Adding an MPEG-4 encoder that can interface with any manufacturer’s digital radio is another cost-effective option. This encoder can take HD/SD SDI, composite video signals, while still providing BCRYPT and AES 128 and 256-bit encryption. Users can upgrade existing encoder or decoder sites by employing a simple installation kit that includes a power and video cable. In many cases, these upgrades will take less than 30 minutes.
Field Example:
The Delaware State Police (DSP) offers an excellent example of an agency that has successfully transitioned its existing MPEG-2 infrastructure to MPEG-4. When the time came for the agency to purchase new aircraft, it decided to update its transmitters to MPEG-4 based units. It already had an extensive receive system, a fairly new system that includes central receive sites, mobile command units and handheld receivers. Instead of replacing the receivers outright, DSP installed an external decoder that bypassed the internal decoder to update the receive systems to handle both MPEG-4 and MPEG-2. This simple installation saved the agency close to $15,000 per site by upgrading the existing systems.
The Final Word:
The best course of action for law enforcement, fire, rescue and security operations departments is to transition to MPEG-4-based systems to take advantage of the technical power offered by the standard. With available equipment upgrades that encompass both MPEG-4 and MPEG-2 capabilities, they can bring their agencies into the MPEG-4 family, while staying in touch with its installed MPEG-2 cousins, thereby maintaining interoperability.
