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JPEG 2000 Compression Over IP

Sat, 04/30/2011 - 8:45pm
Chin Koh, Director of Product Management at Nevion

The way forward for cable companies.

JPEG 2000 was developed as a compression technology for images – but not necessarily for video. Even so, the benefits of JPEG 2000 are leading to a reevaluation of the codec technology in video applications, especially in conjunction with IP transport. As more cable operators shift to IP transport, learning the finer points and benefits of this comparatively new codec can be useful.

For the cable industry, the benefit to using JPEG 2000 would be in ensuring the high quality of HD video.

Established as an international standard in December 2000, JPEG 2000 is a wavelet-based image compression standard. In the realm of video, its intra-framebased encoding scheme limits losses to a single frame or less.

Figure 1 - Uncompressed vs. Compressed/Decompressed w/JPEG 2000

Any distortion can drastically reduce the usability of content. JPEG 2000’s combination of very high quality, very low latency – typically 1.5 frames or less – and cost efficiency provides the opportunity to meet many urgent challenges faced by today’s cable companies.

The demand for video content transport is increasing dramatically, driven by the number of cable and TV channels, as well as the need to transport video to other sources, including mobile devices, and directly to end users. The advent of HD has also increased bandwidth requirements for broadcast contribution systems.

Legacy infrastructures such as satellite and ATM are expensive and offer limited capacity suitable for the transport of HDTV. IP offers cable companies an easy and efficient way to avoid costly infrastructure overhauls while staying competitive and moving with the rising tide of HD adoption.

Video over IP offers the flexibility to scale bandwidth to provide just the right amount of throughput to deliver content. Unlike SONET, the need for 160 Mbps of bandwidth does not force the user to consume two OC-3 circuits (155 Mbps x 2), essentially wasting 150 Mbps of unused bandwidth. Standardized and highly flexible, IP can deliver guaranteed quality of service, as well as low capex and opex when properly engineered and managed.

Cable companies and broadcasters, however, must have the confidence that IP can deliver consistent high quality, and they must be assured that it comes with the essential control, monitoring and management tools the industry expects.

COMPELLING BENEFITS FOR ALL VIDEO TRANSPORT NETWORKS
JPEG 2000’s underlying structure is the key to its advantage. The highly flexible code stream obtained after compression of an image is scalable and can be decoded in a variety of ways. The high bit rates achieved by JPEG 2000 compression are also critically important. As a standard, JPEG 2000 allows for high bit rates – much higher in implementation than H.264.

This is key for high-quality transport because bandwidth may be limited to certain infrastructure types, but bandwidth limits may not necessarily be crucial. For example, HD will not fit into Gigabit Ethernet or OC-12 (622 Mbps), but the entire pipe can be dedicated. So you can compress very lightly to fit into the pipe and achieve high-quality, visually lossless compression. This also leverages the bandwidth scalability that’s inherent in IP, where video can be transported at a desired rate with JPEG 2000, never consuming more bandwidth than required.

JPEG 2000’s flexibility is evidenced by its deployment over key areas of video transport, including contribution and primary distribution. For contribution networks, particularly those with bandwidth limitations, it’s the codec of choice for broadcasting live sports content from outside broadcast events to studios and intra-facility (campusto-campus) video transport.

Cable operators can use JPEG 2000 compression in local channel feeds to the headend to ensure the highest-quality contribution into the cable network.

Figure 2 - Click to ENLARGE image

QUALITY, SCALABILITY AND LATENCY
JPEG 2000 is perhaps best known for the very high quality of its output. At high bit rates, 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 frame by 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.

With sufficient data, JPEG 2000 offers very 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 intraframes 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 both lossless and lossy compression through a single algorithm in a unified code stream. Video can be coded into a mathematically lossless bit stream but rate-limited into a lossy bit stream. 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.

JPEG 2000’s very low latency 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.

Because it doesn’t include motion prediction, JPEG 2000 compression is less complex than H.264. With MPEG-2 and H.264, the encoder must be very efficient and is of much higher complexity than the decoder. In contrast, JPEG 2000 encodes and decodes are nearly equally complex.

Cost-efficient 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.

HIGH QUALITY ACROSS THE VALUE CHAIN
Content distribution is a complete value chain, with multiple processes acting on the initial source video before it’s displayed for consumption. Its value is determined solely by the quality at the final destination. Every stage in the chain must be carefully managed and controlled according to the requirements of the whole, rather than just those of the individual node.

Thus, no node in a transport network is independent. An unsuitable codec used for contribution transport results in extremely low-quality content at the distribution end – and massive viewer dissatisfaction.

JPEG 2000 offers the ability to lightly compress video, allowing multiple encode and decode cycles to be carried out with minimal impact on the quality of the video.

Since the goal is to deliver maximum quality to the viewer, and given the cost of bandwidth, JPEG 2000 compression is optimally positioned to deliver the highest quality possible. JPEG 2000 can deliver both bandwidth savings and pristine content for downstream processing. Preservation of upstream quality supports enhanced quality in downstream processing, which results in satisfied content consumers. 

LIVE EVENTS, TELEMEDICINE, DIGITAL CINEMA AND MORE
JPEG 2000 over IP is poised to make a dramatic impact in particular applications where very low latency and visually lossless quality are critical. Already the standard for digital cinema, JPEG 2000 over IP transmission of live sports from venue to studio, global telemedicine applications requiring long-distance transport and distance learning are being seen with increasing frequency.

Figure 3 Live surgery transmision over IPIt’s also ideal for satellite and medical imagery, file-based transfer, surveillance and archival purposes. For applications that require a high-quality input to the post-production process, JPEG 2000 offers distinct advantages over MPEG-2, where image quality is degraded in compression.

Late in 2009, a JPEG 2000 over IP solution enabled transmission of an extremely highquality, low-latency and error-free live surgical procedure. Traveling from Norway to South Korea, through 18 connected networks on a more than 20,000-kilometer route around the globe, the transmission made history, traversing a greater distance and a greater number of interconnected nodes than any previous telemedicine application. There is perhaps no greater testament to the power and possibilities of JPEG 2000 compression over IP than this highly successful application.

PERFECTION IS IN THE DETAILS
While the benefits of JPEG 2000 compression for networks of the future cannot be denied, the benefits it delivers ultimately depend upon implementations of the technology. JPEG 2000 as a technology is relatively young compared with MPEG-2.

Considering the ongoing technology improvements, JPEG 2000 implementations can only evolve to deliver increasing gains in quality. Currently, the options for JPEG 2000 compression are relatively limited, with almost all implementations based on the same chip technology. For a JPEG 2000 implementation to differentiate itself from the rest, the codec must be optimized to meet and exceed expectations on quality and latency. The engineering, optimization and manipulation of compression algorithms and processing ultimately define downstream video quality.

The JPEG 2000 codec provides tremendous opportunity to next-generation IP networks through its scalability, low latency and capability to reach high bit rates. With the scalability of IP networks, the optimal amount of compression can be applied with the minimum amount of bandwidth. Any two nodes can be connected in real time, without the need to establish permanent circuits, thus providing extreme flexibility in bandwidth distribution.

For these significant gains, JPEG 2000 and IP are a perfect match, complementing each other with flexibility and scalability while delivering the highest video quality that broadcasters and service providers have come to expect from professional contribution transport.

E-Mail: marketing@nevion.com

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