DTS And DVD-Audio
Dear Gary: I wanted to point out a fundamental flaw in DTS’ arguments about DVD-Audio that you echoed in your recent Editor’s Couch. DTS claims that making DTS a mandatory audio feature in DVD-Audio will allow millions of players to be compatible with future DVD-Audio discs. This is incorrect. DVD-Audio is so different from DVD-Video that today’s players can’t play the discs no matter what format the audio is. In addition to watermarking and copy protection differences, the audio contents are stored in a different place than the video contents. Even today’s DTS-aware DVD-Video players wouldn’t be able to find the DTS tracks on a DVD-Audio disc. The only way to make discs backwards compatible is to put a duplicate copy of the audio in the video zone (thus cutting the playback time in half). Since this works just as well for Dolby® Digital and PCM as for DTS, yet is compatible with all existing DVD-Video players, not just new DTS-aware players, DTS’ complaints don’t hold water.
Jim Taylor, Widescreen Review’s DVD Evangelist
Editor Gary Reber Comments:
The point I wanted to make is that DVD-Audio shouldn’t be “so different from DVD-Video and DVD-ROM that today’s DVD-Video and DVD-ROM players can’t play the discs no matter what format the audio is.” The argument I intended to make in Issue 30 was as true for Dolby Digital as it was for DTS Digital Surround. In the case of Dolby Digital, there would be compatibility with all existing DVD-Video players, since every one sold had that feature, as you point out. When I wrote that article it appeared that DVD-Audio would not have backwards compatibility with DVD-Video or DVD-ROM, though the WG-4 has stated that they will take up the matter of “optional” formats such as DTS Digital Surround and Dolby Digital after they have issued Version 1.0 of the DVD-Audio standard. I look forward to your future article which will address the technical issues related to this matter. Interestingly, the DVD Forum announced on February 9 that it has approved version 1.0 of the DVD-Audio specification, and that copies of the published format book will be available by early spring of 1999. The new spec includes a modification to the initial draft that addresses this backward compatibility issue. The DVD Forum has now reserved one sector of the disc for DVD-Audio PCM and a second sector reserved for DVD-Video content. Thus, this new “universal” disc can contain two versions of an album, one with DVD-Audio PCM and the other in the DVD-Video format, playable on existing DVD-Video players. The video element of this section is likely to be still graphics and text screens that take up little of the disc’s bit budget. In setting the new modified standard, the DVD Forum eliminated the requirement contained in the DVD-Video specification requiring a compulsory PCM audio stream in the Video sector of the DVD-Audio disc. This was done because the inclusion of a PCM audio stream (1.5 Mbps data capacity) in the Video sector would not leave enough disc space for DVD-Audio multichannel PCM. Thus, dropping the requirement for linear PCM in the DVD-Video portion of the disc, leaves only Dolby Digital (mono/stereo minimum, but could be 5.1) as a mandatory requirement for audio content. Therefore, the Video portion of the DVD-Audio disc now can have a Dolby Digital track (up to 5.1 channels) by itself. Presumedly DTS Digital Surround, which is classified as an “optional” format in the DVD-Video standard, will be sanctioned as well. As DTS would require 1.5 Mbps of data capacity, the inclusion of a DTS Digital Surround audio stream in the Video sector may not leave enough disc space for DVD-Audio multichannel PCM. Interestingly, DTS has argued to the DVD Forum that version 1.0 should provide for backwards compatibility with the installed base of DVD players and include DTS Digital Surround (DTS Digital Out) capability as a playback requirement of DVD-Audio players. In a twist of fate, the DVD Forum, recognizing the merits of the DTS proposal, went ahead and provided for backwards compatibility but, unfortunately have limited, once again, the “mandatory” player requirement to Dolby Digital, which has mono and stereo capability as well as 5.1-channel (at up to 448 Kbps). DTS Digital Surround is a 5.1 format requiring up to 1.5 Mbps. Thus, it appears that politics has prevailed again over consumer interests. The change, in any event, should enable the DVD-AudioV(video) disc to contain all the combinations of high bit rate/sampling multichannel PCM while maintaining compatibility with the existing user-base of DVD-Video players.
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