Broadcasting infrastructures today must be flexible and highly efficient. Contribution quality content comes from a wide range of sources — satellite, fiber, and, more recently, Ethernet. A single feed may feature a mixture of fiber and satellite routing, and with the increasing use of IP, new complexities and challenges come to the fore.
In addition to compatibility issues, mixing content formats and sources requires encoding, decoding and re-encoding, which can cause signal degradation. At the same time, rising adoption of HD, 3G and more live programming require the highest quality content.
The good news? Advanced compression schemes such as JPEG 2000 provide visually lossless compression with very little degradation even after multiple encode/decode cycles. New monitoring and control capabilities in the form of integrated software solutions provide comprehensive monitoring, and control across the video transport chain ensuring quality of service.
There are a range of options for advanced, professional-grade compression including MPEG-2, H.264, and JPEG 2000. Ultimately, network infrastructure, bandwidth requirements and budget all help to define the “right” choice for each circumstance.
While MPEG-2 and H.264 are good options for next-generation multimedia applications, a strong case can be made for JPEG 2000, whose advanced intra-frame based encoding provides a degree of flexibility and control not found in other compression schemes. The surge in the amount of video transport applications requiring both very low latency and very high visual quality make JPEG 2000 an optimum solution to meet the demands of a video landscape rapidly moving toward HD.
JPEG 2000 is a wavelet-based image compression standard originally developed as an image — not a video — codec. In the realm of video, its intra-frame based encoding scheme limits losses to a single frame or less, bringing vital benefits, especially with the expectation that HD provides high quality, and any distortion can drastically reduce the usability of content.
In fact, JPEG 2000’s underlying structure is the key to its advantages. The highly flexible codestream obtained after compression of an image is scalable and can be decoded in a variety of ways. The high bitrates achieved by JPEG 2000 compression are also critically important. As a standard, JPEG 2000 allows for high bitrates — much higher in implementation than H.264. This is key for high quality transport, because certain infrastructure types might impose bandwidth limits that are strict, but not severe. For example, HD will not fit into Gigabit Ethernet or OC-12 (622Mbps), but the entire pipe can be dedicated. You can compress very lightly to fit into the pipe and achieve high-quality, visually lossless, compression. This also leverages the bandwidth scalability that is inherent in IP, where video can be transported at a desired rate with JPEG 2000, never consuming more bandwidth than is required.
—Image Quality
JPEG 2000 is perhaps best known for the high quality of its output. At high bitrates, no artifacts are perceptible, and at lower bit rates, video quality tends to degrade gracefully. JPEG 2000 operates on the entire frame while other compression schemes require the image to be broken up into smaller blocks, causing quality to diminish unevenly and to vary from frame to frame. This creates the visually annoying digital artifact known as blocking. With JPEG 2000, quality loss occurs evenly across the entire frame and appears visually as blurring, which is less visually disturbing than blocking. Blurring occurs naturally with the eye and people are accustomed to this due to their experience with analog.
Even with extreme compression, JPEG 2000 compressed images degrade with subtle blurring — not annoying blocking and tiling.
With sufficient data, JPEG 2000 offers accurate rate control. If there is sufficient content to compress, the desired rate will be consumed to provide the highest quality possible. This is not the case with motion-predicted codecs where intra-frames require many more bits relative to predicted-frames and bidirectional-frames, resulting in substantial quality variation from frame to frame. The JPEG 2000 standard also provides lossless and lossy compression through a single algorithm in a unified codestream.
Video can be coded into a mathematically lossless bitstream but rate-limited into a lossy bitstream. JPEG 2000 lossless compression provides bit-perfect reproductions with absolutely no difference between the source and the output video. JPEG 2000’s error resilience is another compelling benefit, providing resilience against bit errors introduced by noisy communication channels.
Low Latency, Low Complexity… Low Cost
JPEG 2000’s low latency — typically 1.5 frames or less — is critical for live and interactive applications. Its low latency is due to the fact that each frame is coded separately and independently. The relatively low complexity of JPEG 2000 also provides a cost advantage. As it does not include motion prediction, JPEG 2000 compression is less complex than H.264. With MPEG-2 and H.264, the encoder must be efficient and is of much higher complexity than the decoder. In contrast, JPEG 2000 encodes and decodes are nearly equally complex. Lower cost and less complex, it is also efficient in terms of power consumption and space requirements. JPEG 2000 achieves higher port density in a smaller amount of space than H.264.
Ensuring high quality content does not end with successful, low latency compression. Monitoring and controlling that content is equally significant. There has never been a better time to take advantage of sophisticated market solutions that mitigate transport risks, eliminate signal interruption, and ensure that high quality is maintained across the video transport chain.
Comprehensive Control + Monitoring
The most effective in-service monitoring systems ensure that services achieve target quality-of-service standards 24 hours a day, 365 days a year. These state-of-the-art video, in-service monitoring systems are able to provide centralized, non-intrusive monitoring of a large number of DVB-ASI, HD/SD-SDI and video-over-IP traffic. The most comprehensive systems monitor integrity, presence and activity on each channel, allowing users to pinpoint quality of service issues and proactively correct problems before they affect services. The support for video over IP includes wire-speed monitoring of video over IP traffic at the Ethernet, IP, UDP and RTP layers, enabling the monitoring of high video-over-IP traffic of different formats without the risk of signal interruption.
Systems are designed for passive monitoring of DVB-ASI, HD-SDI and SD-SDI signals, according to DVB and SMPTE recommendations. Often this remote video circuit monitoring is provided through a built-in web interface, which details information about each transport stream — testing signals without breaking any feeds, monitoring multiple signals at once, and pinpointing signal failures down to the transport stream level.
Systems such as these monitor automated Service Level Agreements (SLA) compliance and provide valuable input to create SLA reports. Built-in web interfaces provide access for local monitoring and configuration, with SNMP And XML for remote access and reporting.
Adherence to standards is also a critical function. DVB-ASI signals are checked according to ETR 290, SD-SDI signals according to SMPTE-259 (EDH) and HD-SDI signals according to SMPTE-292. The DVB-ASI measurement and monitoring process follows the recommendations of ETR 290 and is augmented by service critical analysis. SD-SDI monitoring makes use of EDH checks with extensive analysis that includes embedded audio of up to 16 channels. HD-SDI monitoring utilizes check words in the HD signal as defined in SMPTE-292.
Modular platforms are designed to integrate with larger network management systems or third party systems via SNMP, providing complete monitoring and control and end-to-end network management.
Implementation Holds The Key
Specialized knowledge is required as well as the correct products to maximize the quality, flexibility, and scalability that the latest technologies — JPEG 2000 compression, monitoring and control among them — can bring — ultimately, the benefits these technologies deliver depend upon their specific implementations. Keeping abreast of the latest technological developments and the equipment providers behind these innovations are crucial in successfully handling multi-format content and assuring that your infrastructure is ready for the future.
Dr. Eugene Keane is president of Nevion’s Media Networks Division. He’s based at Nevion’s U.S. headquarters in Oxnard, California and has more than 20 year’s experience providing video transport solutions to carriers around the world. Eugene founded Video Products Group (VPG) which was acquired by Nevion in 2008. His work with the organization extends back to 1989 when he worked for PCO, a joint venture between Plessey and IBM, where he led the fiber-optic video transmission group, which subsequently grew into VPG. For over twenty years under several different corporate umbrellas, Eugene has provided vital technology and business leadership for the team developing Nevion’s carrier-class Ventura solutions for video transport service providers. He holds EE, ME and PhD degrees from University College Cork, Ireland.