The quality and clarity of audio, text, and video signals used in mobile phones, computer networks, and EPS devices are among the highest priorities for communications companies and device manufacturers. The race is on to deliver wireless video pictures to handheld phones, and hardware and software providers are jockeying for position. The companies with the best resolution stand to gain billions in the sale of new products. Bit telecommunications companies aren't the only runners in the lossless compression race. The same challenges concern the Internet, television, fax machines, digital photography, printers, etc. Never before has the topic of lossless compression been so topical.
That's why the recent publication of Lossless Compression Handbook by Academic Press (an imprint of Elsevier Science) is so timely. The publisher is billing this tome as "the first comprehensive book that is solely devoted to lossless compression." The 454-page hardback contains 21 chapters written by the world's leading experts on the theory, techniques, applications, and standards surrounding lossless compression.
All engineers and computer scientists who deal with compressed images, text, and data for use in wireless and wired communication systems are affected by the integrity of the process by which the signals are transferred. Lossless Compression Handbook explains the process of compression and transmission of multimedia signals (images, text, audio, and data) so that the decompressed or reconstructed data exactly match the original. Since most signals are coded and compressed to be transmitted, the need for higher quality and accuracy through lossless compression is of absolute importance and highest priority.
Who is this book for? Engineers, scientists, and other professionals who deal with image processing, signal processing, multimedia systems, and wireless technology. It's for "anyone who has a problem that requires compression," says the book's editor Khalid Sayood, a professor in the Department of Electrical Engineering at the University of Nebraska-Lincoln. Though he's an academic, Sayood insists the book is not a textbook, but rather a "reference volume."
The book is divided into five major parts: Theory, Techniques, Applications, Standards, and Hardware. As with most applied technologies, the standards section will be of particular importance to practicing design engineers. In order to create devices and communication systems that can communicate and be compatible with other systems and devices, standards must be followed, and they'll need to know them. Software developers will also benefit from this section, says Sayood.
Here are some of the other topics covered in the book: Information Theory behind Source Coding; Complexity Measures; Universal Codes; Huffman Coding; Arithmetic Coding; Dictionary-Based Data Compression; Burrows-Wheeler Compression; Symbol-Ranking and ACB Compression; Lossless Image Compression; Text Compression; Compression of Telemetry; Lossless Compression of Audio Data; Algorithms for Delta Compression and Remote File Synchronization; Compression of Unicode Files; JPEG-LS Lossless and Near Lossless Image Compression; The CCDS Lossless Data Compression Recommendation for Space Applications; Lossless Bilevel Image Compression; JPEG2000; PNG Lossless Image Compression; Facsimile Compression; and Hardware Implementation of Data Compression (including a section on Video Compression Hardware).
(Warning: This not a book for casual bedtime reading. It is filled with charts, tables, and mathematical equations and not for people who majored in liberal arts.)
As with any technology, lossless compression has its application niches. Lossless compression is most important for content that leaves no margin for error, says Sayood. For example, if you lost a frame of video or some of the higher frequencies of a music track, for example, you probably wouldn't even notice. But if you compressed your tax return using lossy compression and in it arrived at the IRS office missing even just a single decimal point, imagine the consequences.
Lossless compression is more commonly used in text, data, image, and audio applications than in video applications, says Sayood. "For the foreseeable future, lossy compression will continue to be the dominant sort of compression in the broadcast video world," says Sayood. He's seeing more interest from the movie industry, where there is a perceived need for lossless compression for the transmission of Digital Cinema and for the archiving of high-resolution HDTV video.
There's also a lot of action on the lossless front in the audio industry, according to Sayood. He says researchers are currently working on "next generation" audio file formats that will allow users to "handle files in their native compressed form." The problem with current audio compression schemes like MP3 files is that they have to be de-compressed before you can edit them or work with them. In the near future, we'll be seeing improved audio file formats that allow editing and other types of manipulation without the need to decompress first.
Another key application area that is covered in length in this book is the use of lossless compression for digital still images. JPEG has dominated this arena, and for good reason, according to Sayood. "JPEG is such a nice standard," he says. "It is efficient, effective, and elegantly simple.
"When JPEG first came out, it had two parts to it, both lossy and lossless," says Sayood, but the lossless "add-on" to JPEG "didn't get much attention," he says. Nevertheless, development work on lossless JPEG, aka JPEG-LS, has continued. In fact, it is "almost here," he says; the specification is currently "wending its way through committees." It's also the subject of an entire chapter in this book. There is also a chapter on JPEG2000, which Sayood describes as "a broader compression standard that is mostly lossy but with some lossless components."
Where is the field of lossless compression headed? Well, ever upward, according to Sayood, who seems confident of the scientific community's ability to make progress in this area. As lossless compression methods steadily continue to improve, they will continue to replace lossy techniques, which are inherently inferior. There will be some exceptions, however; and no quantum leaps are predicted.
But no matter which scheme suits best—lossy or lossless—the general need for compression seems boundless, says Sayood. Even given lots of bandwidth, people will still demand compression, he says. So compression will always be a popular topic. Sayood observes that: "data tends to expand to fill the bandwidth. You give people more bandwidth and they find more ways to fill it up. We're always going to need compression."