PC DVD Technology

Mpact Media Processor Technology Offers First Low-Cost, Home Theater-Quality DVD Solution for PCs

Over the next several months many companies will be introducing PC-based DVD products and making a lot of bold claims about quality and features. Looking just at the specifications, it may seem like there is little difference between DVD products from one company and another. Users may mistakenly assume that because a product boasts MPEG-2 video or Dolby AC-3 audio, it will be the same as any other DVD product.

DVD may be a standard, but not all PC DVD playback systems will be created equal. And when it comes to PC DVD, there are many areas where video and audio output quality and system functionality can be compromised while still technically complying with the DVD standard. In the rush to bring PC DVD products to market, some PC manufacturers may choose less than optimal hardware-only solutions or sub-standard software-only solutions, resulting in products that will disappoint users seeking the DVD experience.

Movies are the DVD application getting the most attention today, and while compelling, this is only one possible use for DVD's unprecedented video and audio quality. DVD's predecessor, the CD-ROM, has provided us with a wide variety of applications -- from games to game shows to encyclopedias.

Similarly, DVD promises a rich array of interactive entertainment and education applications as multimedia software developers focus more of their attention and resources on the growing availability of PC DVD playback systems equipped with MPEG-2 video and Dolby Digital audio playback. Dataquest predicts 63 million DVD drives will be shipped in PCs by the year 2000. The rapid deployment of DVD will create a new standard for PC video and audio. PC DVD solutions delivered today will need to meet or exceed these quality expectations or risk becoming obsolete just months after purchase.

Software-driven media processor technology is an ideal solution for developing PC DVD products. Combining the best of both worlds -- hardware performance with software flexibility -- Mpact media processor technology delivers the highest quality DVD available today, and ensures that users will be ready for new DVD applications that will arrive in the near future.

 

PCs at the Crossroads

The consumer multimedia PC is at a crossroads of sorts. Until now, multimedia PCs have been getting away with the poor quality of software-only MPEG-1 and .avi video and audio. But the next generation of multimedia PCs -- including a new category of computers for the home sometimes called "PC-TV" -- will for the first time go head-to-head with traditional consumer electronics devices. In electronics stores and throughout the homes of millions of consumers, multimedia PCs will be increasingly compared directly to televisions, VCRs, Laserdisc players and the new set-top DVD players now coming on the market. The video and audio performance of these multimedia PCs will have to meet a new benchmark -- home theater quality.

Indeed, much of the excitement around DVD is superior video and audio quality. This will make it difficult for consumers who purchase a multi-thousand dollar DVD PC to settle for jerky, artifact-filled video and flat audio, especially when standalone DVD players costing only a few hundred dollars can do much better.

The convergence of consumer electronics and personal computers is introducing new rules to both markets. As consumer electronics devices like TVs and game consoles adopt PC capabilities like Internet access and point-and-click navigation, PCs seeking broad consumer appeal must also adopt video and audio quality that meet or exceed what consumers already enjoy from their far less expensive VCRs and stereos.

 

I Want My PC DVD

Multimedia PCs on the market today are typically equipped to process and display MPEG-1 and .avi video. But without hardware acceleration for these first-generation PC video formats, even the fastest Pentium processors tend to produce blotchy, blocky and erratic video and flat- sounding, poorly synchronized audio. While many PC users are intrigued with any full-screen video running on a PC, no one would mistake it for even basic television quality.

The MPEG-2 video standard employed in DVD is capable of easily surpassing the video quality of today's VCRs, televisions and even laserdiscs. Decoding just the MPEG-2 video portion of DVD, however, requires at least five times the processing power required to decode MPEG-1.

MPEG-2 video is just one of the chores necessary to implement a DVD playback system. Fully functional, home theater-quality DVD playback is more compute-intensive, with technical requirements including 30 frames-per-second of full screen video, bit rates as high as 9.8 Mbit-per-second, six-channel Dolby Digital audio decoding, subpicture decoding, navigation and much more.

According to Bert McComas, President of InQuest (Gilbert, AZ), "Based on my testing and looking at the X86 and PC architecture roadmaps, I estimate that host-based DVD with uncompromised consumer quality could not be delivered at the high end of the PC market until the end of 1998, and would not be in mainstream consumer models until Spring of 1999. Further, it is not clear to me that just because host-based DVD will be feasible in Spring of 1999 that it will be consumers' best choice."

DVD will not end at today's best performance and functionality levels because the quest for ever more faithful video and audio reproduction, as well as extending functionality, will continue to soak up increases in CPU performance. To reap all the benefits DVD is capable of delivering requires more extensive decoding to overcome the "lossy" encoding process used to create DVD content and regain more of the quality of the original video and audio source. This also requires additional post-processing functions beyond the basic requirements of the DVD standard to massage the decoded data to a higher degree of refinement, removing unwanted artifacts and other distortions from the reconstituted video and audio data stream.

 

Separating Wheat from Chaff

The heavy lifting of the DVD playback process is accomplished by a suite of elaborate, mathematical algorithms that reconstitute the compressed DVD video and audio content. Working in parallel, these algorithms must not only separate the various components of the complex DVD data stream, but also attempt to fill in the gaps caused by the encoding process. Developing these algorithms is as much art as it is science, and the quality of the video and audio a viewer experiences depends to a great extent on how well these algorithms do their job. But these algorithms need silicon to run on, and there are basically three choices available:

• Software-only solutions that use the existing host CPU to run the algorithms;
• Hardware-only solutions, also called "fixed-function"
• Media processor solutions: hardware performance with software flexibility

Some manufacturers may explore the first choice, using a software-only solution and relying on the existing host CPU to execute the necessary algorithms. While software is less expensive than hardware and can sometimes be produced more quickly, they will quickly see that the quality of a software-only solution today would be unacceptable to consumers with movie-quality DVD expectations. Although technology demonstrations of software-only MPEG-2 decoding abound, most experts agree that consumer-electronics-quality DVD using this technology is still several years away from being technically and economically feasible, and will still require assistance from a separate graphics accelerator.

In attempts to rush DVD solutions to market, quality-compromising shortcuts need to be taken if the CPU is to perform not only video decoding, but audio decoding, subpicture processing, copy protection decryption and navigation functions, not to mention the rest of the PC's functionality.

In order to keep up with the huge amount of data flowing from the DVD disc, the software-only solutions must take a triage approach to data processing, ignoring certain parts of the data stream so that others may survive. When divvying up the limited number of CPU cycles available for DVD playback, top priority is usually given to audio decoding because the ears are more sensitive to distortions than the eyes. After that, maintaining the highest possible frame rate is paramount.

The biggest shortcuts are taken with two of the most compute-intensive, but very important parts of the video decoding process -- inverse discrete cosine transforms (IDCT) and motion compensation. Taking shortcuts with either of these processes results in a variety of undesirable artifacts and distortions in the output video.

MPEG-2 uses a highly complex mathematical process called a discrete cosine transform (DCT) during the encoding process (digitizing the original video source) that greatly reduces the amount of information needed to represent each frame of video by eliminating certain data. During playback, a reverse process, called an inverse discrete cosine transform (IDCT) is used to reconstruct the original images.

If there is not enough processing power to maintain the frame rate and perform IDCT, especially when the DVD data rate increases well beyond the nominal 3.5 Mbits per second, the IDCT algorithm is forced to simplify its computations by ignoring certain portions of the transform altogether. If not, all of the pieces that were thrown away during encoding are replicated by the IDCT, image quality will suffer. In this case, the picture loses detail and the video displayed will show "blocking" or large square areas lacking in detail throughout the frame as the crippled IDCT attempts to fudge its duty.

MPEG-2 also uses motion compensation during the encoding process to reduce the volume of data by looking for areas of the picture that move but do not change in detail, eliminating most of this picture information altogether and substituting a much more compact motion vector. Then, during MPEG-2 decoding, the motion compensation algorithm applies the motion vector to the output image to change the positions of individual blocks from frame to frame.

But when push comes to shove as the software decoder struggles to keep up, the motion compensation algorithm may not have time to move all the blocks it needs to, resulting in nonfluid movements within the frame. While usually viewed as jerkiness that results from a too low frame rate, these motion compensation artifacts affect only a portion of the frame, not the entire frame. The body of a person moving across the frame may look all right, but the arm swinging back and forth shows a strange, jumpy motion. Motion compensation artifacts may also appear when highly contrasting or brightly colored areas move across each other.

Makers of software decoders are attempting to compensate for this shortcoming by relying on motion compensation hardware built into a new generation of 2D/3D graphics controller chips. Besides the poor quality of current implementations, this still leaves the host processor stuck with all the rest of the DVD decoding process, including IDCT, audio decoding, subpicture processing, decryption and navigation. In addition, huge amounts of data have to travel over an external bus, which can never perform as well as an integrated solution.

 

Frozen in Time

Another PC DVD option is a hardware-only solution using a number of dedicated decoder chips to perform DVD playback. While at first glance hardware solutions might be appealing because they overcome many of the performance-related issues inherent in software-only solutions, a closer look reveals other considerations that might steer users away.

The first hardware solutions to reach the market typically comprise five major application-specific integrated circuits (ASICs) -- an MPEG-2 video decoder, a Dolby Digital (AC-3) audio decoder, a subpicture processor, a copy protection decryption chip and a PCI busmaster chip -- and require a full-size PCI card to hold them all. The number of devices, the complexity of the board and the size all contribute to higher cost and lower reliability.

Lack of chip-level integration can also lead to DVD quality problems. DVD audio and video, when forced to run through the non real-time Windows PC environment, can lose synchronization. This can happen when using other PC resources while DVD is running (e.g. the phone line rings on the fax/modem and the PC must answer), or as a result of something as simple as the user resizing or moving the DVD window.

Hardware solutions also must rely on the less-than-optimal analog video adjustments (brightness, contrast, color, tint, etc.) of the display monitor to attempt to compensate for how video intended for display on a TV appears on a PC monitor. While the resolution of a PC's monitor is far superior to that of even very high-end TVs, a monitor produces video images that appear darker and less vibrant than the images consumers are accustomed to seeing on their TVs.

But there is another, more subtle problem with hardware-only solutions. DVD is a relatively new and immature technology. The algorithms developed to decode and play back DVD are also relatively new and immature. There is plenty of room for improvement in these algorithms as developers gain experience and a better understanding of the technology over time.

Hardware-only solutions offer better raw performance than software, but the algorithms etched into their silicon are frozen in time, and represent old thinking that is likely to be quickly revised during DVD's initial ramp-up period. It takes time for second and third-generation debugged hardware solutions to come to market. Hardware-only implementations cannot quickly deliver these incremental improvements, and users as well as manufacturers will be stuck with products that quickly become obsolete. The cost of hardware will surely come down, but hardware solutions will be less able to add new features and adapt to changes in the market as DVD and 3D graphics functions merge.

 

The No-Compromise Mpact Solution

Mpact media processor technology from Chromatic Research, LG Semicon, SGS- THOMSON and Toshiba combines the high performance of hardware-only DVD with the flexibility of software-based DVD in a fully integrated, software-scalable solution. The result is no-compromise, home theater-quality DVD audio and video acceleration on a single, software-scalable Mpact chip.

Today, because of its high integration and advanced manufacturing, the Mpact media processor already competes favorably on price with DVD-only accelerator chips. But a single Mpact media processor is also software-scalable, capable of supplying the PC's graphics, audio and modem capabilities just by adding additional Mpact Mediaware software modules. As PC manufacturers migrate one or more of these capabilities to the Mpact media processor, thus eliminating the cost of separate graphics, audio and modem chips, the cost of Mpact DVD acceleration approaches zero.

Unlike the vast majority of emerging solutions for PC-based DVD playback, the Mpact DVD solution meets or exceeds all DVD specifications, for example:

• Mpact technology's consistent 30-frame-per-second MPEG-2 video decoding, combined with IEEE-1180 IDCT and full motion compensation, guarantee full-motion video that is crisp, clear and virtually free from distracting artifacts. In other words, DVD playback from a PC looks as good as from a stand-alone consumer DVD player.
• The tight integration of Mpact audio and video capabilities includes exclusive, patented Avsync(tm) technology which uses a real-time process to ensure synchronization of DVD audio and video.
• Mpact DVD technology allows PCs to display on a standard television screen and on the PC's monitor.
• Mpact technology is among the first PC DVD playback systems that can play encrypted content, such as Hollywood movies, via approved CSS (Content Scrambling System) decryption.
• Mpact DVD technology provides true, 6-channel Dolby Digital audio for playback on 6 speakers, including an interface to home stereos with Dolby Digital capabilities. It can also re-encode Dolby Digital audio into Dolby ProLogic audio on the fly, enabling an interface to standard Dolby ProLogic audio-equipped home audio systems.
• Mpact DVD is also the first to offer SRS TruSurround technology, enabling a standard two-speaker PC or home stereo audio system to replicate the impact of 6-channel Dolby Digital audio by fooling the ear into hearing 6 virtual speakers around the listener.
• A DVD player application called Entertainment Center, developed specifically for Mpact technology by Software Dynamics, Inc., provides a consumer-friendly interface to all Mpact DVD features, including navigation, selectable aspect ratios and camera angles, subtitles and much more.

Lists of features are certainly no substitute for hands-on testing. Few consumers buy televisions or stereos based on specifications. Rather, they evaluate picture quality and sound, often in side-by-side comparisons. This simple guide may prove helpful when comparing PC DVD playback products:

 

PC DVD Issue	Cause	Mpact Solution
Video
Jerky motion across entire frame, particularly in high-action scenes with high bit-rates	Frame rate too low or inconsistent due to insufficient processing power and/or memory bandwidth	Mpact media processor capable of 3.6 billion operations per second coupled with Rambus high-bandwidth memory, working with X86 CPU. Enables full-screen, 30 frame-per-second MPEG-2 decode at maximum DVD bitrate of 9.8 Mbits/sec.
Jerky motion within frame, other motion artifacts	Poor motion compensation	Exact motion compensation for artifact-free playback
Poor detail, blockiness, fuzziness, tearing	Poor Inverse Discrete Cosine Transform (IDCT)	IEEE-1180 compliant IDCT for crisp picture quality with minimal noise
Can't play copy-protected content	No decryption of Content Scrambling System (CSS)	Approved CSS decryption
Video appears dark on computer monitor	Lacks real-time brightness adjustment	Chromabright(tm) real-time digital brightness adjustment
Video colors appear flat, dull	Lacks real-time color processing	Chromadjust(tm) real-time digital color processing
Can't display all encoded subpicture tracks	Not implementing full subpicture decoding	Full sub-picture decoding (e.g. subtitles)
Can't fast-forward, rewind, pause, frame-by-frame advance, chapter search or chapter advance	Lacks full DVD navigation implementation	Full DVD navigation
Can't change camera angles, languages	Lacks full DVD navigation implementation	Full DVD navigation
Can't display letterbox or other encoded aspect ratio options	Not implementing aspect ratio selection	Supports 16:9 wide screen and 4:3 letterbox display
Can't perform Pan & Scan (pieces of movie are indiscriminately chopped from the sides)	Not implementing Pan & Scan	Supports Pan & Scan
Audio
Loss of audio/video synchronization	Lacks real-time synchronization capability	AVsync technology for real-time audio/video synchronization
No surround sound with two-speaker setups. Flat-sound.	Lacks surround-sound virtualization	SRS TruSurround technology for virtual 6-speaker sound from two standard stereo speakers
Cannot connect to Dolby Digital home audio receiver/amplifier	Lacks digital audio output	Digital audio output

Today, PC makers are striving to meet consumers' "no compromises DVD" expectations with high-quality, low-cost DVD solutions. By combining the key advantages of software-only and hardware-only DVD playback technologies, the Mpact media processor's unparalleled combination of affordability, performance and versatility offers an ideal solution for home theater-quality DVD, as well as any other applications that may come along in the future.

However, PC DVD is only the first mainstream application for media processors. Because of its high-bandwidth, supercomputer-like architecture, and software-scalability, a single Mpact media processor is capable of accelerating a whole host of multimedia functions simultaneously with top-tier performance for each function. Mpact media processor technology offers virtually any combination of multimedia capabilities with constantly improving Mpact Mediaware modules available for 2D and 3D graphics, videophone, home movie editing, audio, telephony, fax/modem and more.

Working in conjunction with an X86/MMX CPU, Mpact media processor technology can provide all of these capabilities on a single system with the same price/performance leadership it brings to DVD.

 

Chromatic Research, Inc.

Chromatic Research, Inc. is the pioneer and leader of the fast-growing media processor market. It is also the world's first "chipless" semiconductor company, based on a unique business model whereby the company's semiconductor partners LG Semicon, SGS-Thomson and Toshiba co-develop, manufacture and sell the Chromatic-architected Mpact media processor and Chromatic Research develops and sells the enabling software called Mpact Mediaware. The software-scalable Mpact media processor solution can integrate a full range of multimedia functions, including DVD, home movie editing, videophone, 2D/3D graphics, audio, telephony and modem. Founded in 1993, the company is privately held. Chromatic Research, Inc., 615 Tasman Drive, Sunnyvale, CA 94089-1707.