| Video Noise March 2006
More High-Definition Optical
Disc News
Film studios have asked the makers of
high-definition disc players to limit their hi-def video output to the High Definition
Multimedia Interface-High Bandwidth Digital Copy Protected interface, or HDMI-HDCP. The
studios said they wanted DVD-equivalent resolution via DVI or analog component connections
because this will somehow make it harder for pirates to create HD duplicates. Neither DVI
nor analog component connections include any protection against copying or pirating.
Wouldn’t it be annoying to buy a new HD DVD or
Blu-ray player and find out that, using your older HDTV, you can’t watch movies that
look any better than your regular DVDs? The equipment manufacturers have proposed that
each HD disc include a "flag" that will tell the player whether or not it’s
OK to output hi-def video via the player’s analog video and/or DVI outputs. If the
studios accept this proposal, they will then have full control over what video resolution
you will be able to see on your "legacy" HDTV. Never mind that serious pirates
will defeat HDMI copy protection anyway, and convert the video to any unprotected format
they feel like using.
It’s not clear how customers will find out whether or
not they can view any given HD DVD or Blu-ray disc in true HD on their current
display. Will there be a warning on each box stating that the disc "Requires
HDMI-HDCP interface for high-definition playback"? We shall see.
Any good news?
The only good news on the Blu-ray/HD DVD front is that
some studios have decided to offer movies in both formats, which makes player choice less
of an issue. Furthermore, manufacturers who are members of neither camp have shown that
it’s possible to make a player that would play both hi-def formats, much as
today’s universal players can play SACD and DVD-Audio along with all CD and DVD-Video
formats.
Anything else I should know?
Can your surround decoder decode DTS-HD and Dolby TrueHD
signals? I didn’t think so. The DVD players themselves do that decoding, at least for
the time being. But that leaves you at the mercy of your player’s surround-sound
chipset, and decreases the usefulness of the surround processor in your system. To get
high-definition movie sound, you’ll need six or seven or eight individual analog
audio interconnects, which defeats the major advantage of the HDMI interface: one cable
that handles all video and audio signals. Presumably, surround decoders will
eventually have internal DTS-HD and Dolby TrueHD decoding, and HDMI-HDCP cables will
transmit high-resolution digital audio to the surround processor; but until then, playing
hi-def discs is going to be a bit irritating.
An analog audio signal sent to the surround processor will
typically be digitized. It will have bass management, LFE crossovers, and time delays
applied per the setup menu, and then be reconverted to analog. But those extra
encode/decode steps always degrade the sound quality. Some expensive surround
processors skip the digital encoding of incoming analog signals, but most surround
processors and receivers redigitize analog signals -- not the best news for the
home-theater enthusiast seeking great sound quality without having to spend an arm and a
leg on a surround processor.
Higher-definition audio
With the HD DVD and Blue-ray high-definition formats,
the maximum sampling rate of digital audio signals encoded on an optical disc format will
increase to 384kbps -- double DVD’s digital maxima of 192kbps for two-channel sound
and 96kbps for 5.1-channel. The higher rate will usher in a whole new generation of D/A
and A/D chips.
Where do the eight speakers go?
HD DVD and Blu-ray will be able to have up to eight
discrete channels of sound. You may think that DVDs already have eight channels of sound
via Dolby Digital Surround EX and DTS-ES (discrete), which are often referred to as
7.1-channel formats. However, these are actually 6.1-channel formats: If you use two
center (back) surround speakers, you’re sending one channel to both speakers. But
hi-def optical discs really do have the capability of encoding one additional discrete
surround channel. Some are proposing a new overhead channel, some propose a channel above
the front main speakers, and others want 5.1 with two discrete center surround channels.
It may be the dawn of two new disc formats, but many
questions about them remain unanswered.
...Doug Blackburn
db@hometheatersound.com |
