DVD GROUP AT IMPASSE OVER DUAL-SIDED DVD/CD HYBRID

Prime mover behind dual-sided hybrid is Warner Music Group (WMG), whose motivation is to rekindle flagging CD sales by piggybacking on successful DVD music-video format, we're told. Attempts to reach WMG executives, including Kevin Gage, vp- strategic technology & new media, were unsuccessful. It’s presumed hybrid also might put life into desultory sales of DVD- Audio titles. Those can be played only in DVD-Audio or DVD-Video players, and lack backward compatibility with CD players that’s enjoyed by hybrid Super Audio CDs, which have high-resolution and conventional CD audio layers on single side.

Attempts have flopped to create dual-layer hybrid with DVD- Audio and CD tracks on single side because legacy DVD-Audio and DVD-Video players didn’t consistently find correct layer -- most often playing CD version, and sometimes rejecting disc outright. As result, DVD Forum working group killed proposal for so called Multi-Format disc (CED March 31 p1), even though Forum still was considering changes to DVD hardware specs that would enable hybrids to be read in future DVD players. Even if dual-layer Multi-Format disc were made to work, it was considered likely that backers would run into licensing and royalty issues with Philips and Sony, which hold patents that make dual-layer approach function in rival Super Audio CD format.

Content owners since have turned attention to dual-sided hybrid, but obstacles have been considerable from technical and legal aspects. Industry reports persist that DVD-Audio backers have produced dual-sided DVD/CD, and despite unsatisfactory technical results to date had continued lobby for hybrid. Recent report in Financial Times cited unnamed music executive as saying WMG and Sony would introduce dual-sided disc early next year (CED Sept 17 p2). Sony representatives have told us there was no truth to report, and WMG hasn’t returned calls for comment.

Dual-sided hybrid DVD/CD is being studied by Working Group 2 (WG2) of DVD Forum, which would then report results to Forum’s Technical Coordination Group (TCG), which then would advise Forum’s Steering Committee. Proposed dual-sided Multi Format disc bonds 2 pressed discs together, back to back, to give CD layer that can be read from one side and DVD layer to be read from other. Technical challenge has been that hybrid might fall outside CD and DVD specifications and not play properly.

Thickness of dual-sided hybrid is one technical issue. Red Book CD standard specifies single disc between 1.1 mm and 1.5 mm thick. DVD standard specifies same, by sandwiching 0.6 mm sides for “nominal” thickness of 1.2 mm. Tolerance for each format is -0.1 mm/+0.3 mm. Thickness is critical because (1) transparent parts of disc work with the player optics to focus laser and (2) out-of-tolerance disc might jam in players’ loading trays and, more of problem -- in slot-load type players used primarily for autosound but also increasingly used in home DVD players and PCs. Disc that’s out of thickness spec or proper balance also can create tilt-error problems for reading data.

Original dual-sided hybrid proposal calls for sandwich with 0.9 mm CD layer and 0.6 mm DVD layer, for total thickness of 1.5 mm, right on edge of specification. Even so, experts said 1.5 mm target left no margin for manufacturing tolerances and didn’t take into account real-world manufacturing. Proposal since has been changed, for hybrid 1.566 mm thick. Sources told us discs circulated to WG2 by WMG were thicker. Although WMG measured discs as 1.566 mm, others found discs to be as thick as 1.587 mm. But that’s not main point of contention among WG2 members, we're told. Instead, main sticking point seems to be that discs WMG supplied had no data in CD layer.

Although sample discs could be tested for mechanical performance in DVD and CD players, lack of audio data in CD layer wouldn’t enable testing for compatible playback in legacy CD hardware, some WG2 members argued. They proposed suspending tests until sample were re-manufactured with data in each layer. WMG contended data in CD layer wasn’t necessary, because DVD Forum and its committees have no jurisdiction over CD spec, whose Red Book standard is overseen by Philips acting as agent for itself and CD co-inventor Sony. When DVD Forum’s WG4 tested dual-layer hybrid DVD-Audio/CDs, it didn’t check hybrids on legacy CD players, of which one billion have been sold in last 20 years. Sources said then that was because group was wary of antitrust issues, as DVD Forum had no say-so over CD Red Book spec. WG2’s mandate is to examine proposed hybrid only from perspective of compliance with DVD specs, WMG said, and dabbling in CD spec could present legal problem for Forum.

That issue was raised in past by JVC’s legal department, which warned that DVD Forum did not control Red Book standard and would have to work out any CD issues with Philips. Nonetheless, Jungwan Ko, Samsung engineer who chairs WG2, has insisted, as have apparently other WG2 members, that sample hybrid must have data on DVD and CD layers for group to perform valid testing and present TCG with comprehensive report on hybrid’s viability. Some WG2 members have raised specter of class action lawsuits by consumers if hybrid discs fail to play in any way, or possibly cause damage to playback equipment. Impasse for testing, though, has yet to be resolved, and some WG2 members have requested group seek renewed outside legal opinions before proceeding with compatibility tests.