The Smart Solution for MPEG-2 Editing
Video Technology & Practice DVD, Authoring and 601
DVD Video- An Introduction MPEG-2, along with DV is fast becoming the de facto video compression standard in the age of digital video. The first and most well- known application for MPEG-2 is as a video format for DVD. Although DVD still has to make its breakthrough in Europe in particular, it is already apparent that this 'Super-CD' will have the same success in the storage and video sector as the CD has had in the audio sector. Until recently, the production of DVD video was only feasible for projects in the magnitude of a Hollywood film. However, new low-{;ost equipment for editing in MPEG-2, compiling content (called authoring) and mastering will change all this in the near future. What's behind "DVD"? What features and possibilities can be used for what application and what is already possible today?
The Universal Super-CD As a universal medium, DVD ('Digital Versatile Disk') aims, on the one hand, to become the successor of the CD-ROM as a storage medium for PCs and, on the other hand, to replace the VHS tape. When such a universal medium is defined, it is practically unavoidable that an almost infinite number of parameters emerge, which in the case of DVD have given rise to various sub-formats and sub-definitions. DVD-ROM, DVD-R, DVD-Video, DVD-RAM. In general, there is a difference whether the DVD is to be used as a storage medium for PC data or as an interactive medium. Depending on the intended use, the format and compatibility of the DVD must be taken into account.
DVD-ROM The DVD-ROM is the base for DVD developments. Data cannot be written on to it but it is pressed in the factory from a master. Similar to the CD it is scanned by a laser without being touched and thus it has a virtually infinite service life. Unlike the CD there are double sided and two-Iayer definitions for the DVD-ROM, both of which double storage capacity. Thus, there are definitions for four different versions. DVD 5 is most commonly used at present. The DVD-ROM can be written {like the CD-ROM) with any PC data, which can then be read again by any suitable PC. The type of data is irrelevant as the DVD-ROM merely functions as a large data carrier. However, the DVD-ROM can become a DVD video through the use of a special format {and the corresponding contents). The DVD-ROM can be played back in both DVD-ROM and DVD-RAM drives in a PC.
DVD-RAM The DVD-RAM is a completely different development from the DVD-ROM. The goal was to develop a medium that could be overwritten many times and was as easy to handle as a CD. At present the capacity of the DVD-RAM is limited to 2.6 GB and it can only be used as a 'sealed package', i.e. with a permanent protective cover ('caddy'). With current technology a DVD-RAM can only be read in a DVD-RAM drive in a PC (which can however also read DVD-ROMs). Therefore, the DVD-RAM is suitable as a fast, large removable medium but not as a medium to create DVD videos. Theoretically, a DVD-RAM can also be formatted as a DVD video but in practice there are not yet any DVD players that can read DVD-RAMs. In the future new technology should make DVD-RAM compatible with DVD-ROM or DVD video.
DVD-R DVD-R, which can be written to once, has a special status. In contrast to DVD-ROMs and DVD Videos produced on high-end machines and to incompatible DVD-RAMs, DVD-Rs can be produced with a PC using a DVD-R device (similar to CD-R). Both DVD- ROM and DVD video formats can be used. The DVD-R thus produced is compatible with DVD drives and DVD players (as DVD video). The capacity of the DVD-R is currently limited to 3.9 GB. Developers are working on a version with 4.7 GB storage capacity, which would then be 100% equivalent to DVD 5.
DVD Video In the mid-term DVD video is intended as a replacement for the VHS tape. The conditions are favorable but only on the player market (e.g. video rentals). At present, functionality as in a VHS video recorder is unthinkable. Such equipment for repeated recording is still at the prototype stage. The key advantage of DVD video is its virtually unlimited service life. Even when it is played back for the hundredth time, its quality is still as good as the first time. A DVD video is a DVD-ROM, -RAM or -R with a special format -equivalent to an audio CD, which in turn is a specially formatted CD- ROM. This format includes video, audio and control information. For example (provided the relevant information is available)
15029 Wood,""ille-Aodmond Ad. Wood,""I1'o. WA 9.072 ToC 4253542002 .Fax 4253542005 wwwfasfmu'fimodiocom it is possible to choose among different camera angles, several languages or various subtitles. Naturally, just like with audio CD, it is also possible to jump between separate video sequences and chapters, provided this was taken into account during creation. With standard DVD players all features of DVD video can be used. With a PC, the DVD video can only be played back if the appropriate decoder hardware for video and audio is available.
The Technology Certain parameters are defined for DVD video which allow both interactive Hollywood productions as well as simple films consisting of just one video/audio sequence to be recorded on a DVD.
Video format Common to all DVD videos is the video format: MPEG-2 in the version MP@ML. The data rate can be up to 9.8 Mbps {including all audio, subtitle and other data). Typically, a rate of 2 to 8 Mbps is used, which more or less lies between VHS and good television quality. For example, a 135 minute movie fits on to a DVD-5 with quality that cannot be matched by VHS. Page ratios of 4:3 and 16:9 are supported. Besides the main format MPEG-2 MP@ML, the formats MPEG-2 SP@ML {with reduced resolution) and MPEG-1 are both allowed. These formats are optimized for applications where storage quantity is more important than quality. For example, the MPEG-1 format allows 15 hours of video to be stored on a DVD-5.
Audio formats Audio formats have been debated for a long time: whereas Dolby Digital (AC-3 compression) was chosen in NTSC countries (USA. Japan) at an early stage, MPEG-2 audio (not to be confused with MP3. MPEG-1. layer-lll) was favored in PAL countries (Europe. Australia, etc.). In the meantime both formats have become accepted in Europe. That simplifies the production process considerably and helps make distribution faster. Dolby Digital supports up to six channels (the sixth channel is assigned to the subwoofer so that it is usually written as 5.1) and MPEG-2 even up to eight (as 7.1 ). DVD players that do not support multichannel output only output the left and right channels as a standard stereo signal.
Apart from compressed audio formats it is also permissible to store uncompressed PCM audio. Again, up to eight channels are supported and quality can even be significantly better than with a CD: up to 24 bit/96 kHz (the CD " only" supports 16 bit/44.1 kHz).
Moreover, there are a number of optional formats (SDDS, DTS) which can, however, only be used in addition to one of the above formats. Therefore, at least one of the standard formats (Dolby Digital, MPEG-2 or PCM) must be available on a DVD video. In PAL countries all DVD players (and even the PC hardware which can play back DVD videos) must be able to process Dolby Digital, MPEG- 2 and PCM and output them at least as an analog signal. Only Dolby Digital and PCM must be supported in NTSC countries.
Further information Besides the practical advantages (playback as often as required, small size) the attraction of DVD video is its interactive feature: for example, up to eight versions (e.g. languages) for audio and up to 32 subtitle tracks are supported. Likewise, videos can be subdivided into chapters and one out of up to nine camera positions can be selected without delay during playback. For different versions of a film it is possible to set jump marks at points in the film where the story is to be continued without delay. Naturally, information on authors, titles, etc. is stored.
Two crucial functions are regional coding and copy protection. There are six regional codes that prevent playback of DVD videos with a certain code on players with a different code. For example, DVD videos from the USA cannot be played back on players in China. This copy protection is intended to prevent unallowed, digital copying of commercial DVDs.
DVD authoring
How does the required information get on to a DVD video? What is necessary for print-to-DVD? What data is essential and what data ", is optional? The process of DVD authoring (i.e. the creation of a DVD) still involves a great dear'of work and is thus cost-intensive. This is due partly to expensive encoders (to create MPEG-2 video data) and partly to the applications (authoring software) that are needed to create the program. As most of these authoring packages include all specifications and thus offer an enormous range of possibilities, users of these software packages require special training. Who needs what? Not everyone who just occasionally wants to create a DVD video needs six audio channels, five languages and three camera positions. In most cases no such material is even available.
Fa.t Multimad;a US Inc Woodmv;lIa-A.dmood Ad. Wood;ov"'a, W! Tal 4253542002 .F" 4253542005 wwwf,.fmult;m,d;,oom Therefore, a distinction has to be made between two major applications: Hollywood and corporate.
DVD Authoring Hollywood movies, which are often produced on a large budget, or complex advertising and informative productions (e.g. interactive presentation of a new car, etc.) can indeed benefit from the multitude of possibilities offered bya complete authoring system. Films can be published in several languages and/or with subtitles. The 'Making of ...' can also be available on the DVD video as a separate film divided into several chapters. Film music, also CD-compatible, is also included. In the case of less formal DVDs details on the product being marketed can be accessed directly with jump marks or advertisements can be selected. All this information requires much more than the simple production of video and audio. Rather, the concept of DVD must be taken into account at the shooting stage. In addition, multi-language versions, subtitles and graphics (for the branch menus) have to be created.
Accordingly, the DVD authoring process involves several steps: project planning, 'bit budgeting' (to determine how much information will really fit on to the DVD and which DVD version should be used), video and audio encoding, the actual authoring (i.e. the compiling of all elements to make a program), 'proofing' (simulation of the complete DVD on a computer) and finally mastering and production. c
At present systems with all these functions cost more than $ 300,000. Such systems are usually installed on the premises of special service providers who offer DVD authoring from the beginning (shooting) to the end (completed DVD). A new group of software titles is intended to make the process of DVD authoring simpler without involving the loss of most of the attractive DVD functions. Applications are available for about $ 10,000* that are relatively simple to use and support several versions, languages, subtitles, jump marks, etc. Naturally, these software solutions need appropriate hardware to encode and decode audio and video.
If an interactive DVD video with all functions is to be created, then the authoring process is certainly separate from editing and must be carried out by trained staff. Close planning cooperation is required from the beginning over the entire production period.
Print-to-DVD: the 80/20 principle Only some of the above functions are necessary for the distribution and archiving of marketing presentations and videos, advertisements, rough cuts, etc. on DVD video. As an alternative to the VHS tape, a DVD video with a defined number of sequences/ tracks for direct selection meets almost all of the requirements.
Depending on the format used (MPEG-1 or MPEG-2) and the source material, results can be considerably better than with VHS. In addition, the quality is just as good when the video is played back for the hundredth time as it was the first time. As the method is less complex than a complete authoring procedure, it is also suitable as a means of export for nonlinear editing systems. Instead of creating a VHS copy, the finally edited film is pressed directly on to a DVD video -provided this is supported by the system and suitable equipment is available.
The 'minimum run time' of a DVD video is sufficient for most productions (64 minutes using the highest permissible data rate of 9.8 Mbps) so that it is not necessary to become involved with complex 'bit budgeting' to utilize the capacity optimally.
601 & DVD Video FAST's new nonlinear editing system '601 [six-0-0ne)' is based on MPEG-2. With '601-PrintDVD' (a software option for the output of DVD~ompatible video), it covers the spectrum of production and distribution with the new compression standard.
Technical prerequisites
Within MPEG-2 there are not only various parameters, such as GoP length (GoP = Group of Pictures, i.e. the length of a noneditable MPEG block) or scanning (422P with 4:2:2, MP with 4:2:0) but also various 'packaging formats' for storage and distribution. When video and audio data are stored separate from one another, the term 'Elementary Stream' (ES) is used (for video data). Conversly, you can combine video and audio in packages (multiplex or mux): a 'Program Stream' (PS) is created. A 'Transport Stream' (TS) is also defined. This is a PS that has been reformatted and streamlined for wideband transmission (e.g. via satellite). Incidentally, the type of audio format and the number of audio channels used are irrelevant for this definition.
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15029 Wood;ov;lIa-Redmood Rd .Wood;ov;lIe. WA 98072 Tel 4253542002 .Fa, 4253542005 www ',stm"'t;med;a,om In addition ES for video and various formats for audio are suitable as a source for DVD authoring systems as usually several versions have to be created for different languages, etc.. Some systems even accept PS, with the data being separated again before processing. Notebooks or PCs with MPEG-2 hardware can play back both ES and PS provided the audio format (in the case of PS) is supported. If the processors have more computing power it is possible to decode MPEG-2 exclusively with software. However, this is not yet possible in real time and/or with full resolution and quality.
To create a DVD video it is necessary to embed one or more PS's into the so-called UDF format. This format adds start and end information to the video and audio data so that separate films can be accessed as with an audio CD. The UDF format is done by the writing software, which also controls the DVD-R writer.
601-PrintDVD During editing 601 works with the variant 'Editing-MPEG', i.e. 422P@ML, and uses I-frames only to allow frame-accurate editing. At 50 Mbps the data rate is relatively high as neither motion recognition nor encoding are carried out. Therefore, data for export has to be converted to the DVD-compatible 'Distribution-MPEG', i.e. MP@ML (IPB-frames). As the hardware used by 601 is already based on MPEG-2, 601 makes this process faster. With the software option '601-PrintDVD', 601 allows the output of the created films both as MPEG-2 ES (video) with separate WAV audio and as MPEG-2 PS (with 2 channels of uncompressed PCM audio). Several data rates are available to meet various quality requirements. Using a DVD-R writer and the appropriate writing software several ES's and/or PS's can be stored on a DVD-R as single 'tracks'.
Examples of Applications for 601 With 601 and the '601-PrintDVD' option the user immediately has three applications available: .Creating MPEG-2 ES video and WAVE audio data for direct transfer to professional DVD authoring systems.
.Creating MPEG-2 PS data with 2 channel PCM audio, which can be immediately played back on MPEG-2-enabled notebooks and PCs.
.Direct pressing of a DVD video which contains films created with 601
References on the Internet: http://www.mpeg.org/MPEG/dvd.html (DVD page of www.mpeg.org) http://www.dvd.at/dvd/fact15.htm (glossary in German) http://www.c-{:ube.com/technology/dvd.html (DVD background at C-Cube) http:/ /www .videodiscovery .com/Vdyweb/dvd/dvdfaq .htm I (DVD FAG in English, extremely detailed with all kinds of information!) http :I/WWW .dvdcreator .comlpdf Idvd-pri m e r.pdf (Adobe Acrobat document (English} by Sonic Solutions, which describes the DVD authoring process in great detail}
*Prices and specifications are subject to change without notice
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