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article last updated on
4.14.2007 |
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As wonderful a technology that DVD-Video is, what can possibly be better?
Well, how about High
Definition-capable DVD? Take everything that’s great about DVD-Video but increase the picture resolution from a standard definition 480i (or enhanced definition 480p if you have a progressive scan DVD player) to a high definition resolution of 720p,
1080i, or even 1080p. This article focuses on the next generation High
Definition-capable format, as an optical disc format.
We will discuss the challenges of recording HDTV,
the formats under consideration, and backwards
compatibility issues with the existing DVD-Video
format.
Recording HDTV The ability to record to an optical disc format is a wonderful thing. Anyone who has “burned” a CD-R for data or music knows: random, direct, and quick navigation to the track you want.
There is no need to fast forward or rewind a tape. The ability to record video and audio to an optical disc format like one of the
three recordable DVD formats (e.g.,
DVD-R/RW, DVD+R/RW, and DVD-RAM) is also a wonderful thing.
But can you use DVD-R/RW, DVD+R/RW, or DVD-RAM media to record high definition TV?
No, these recordable DVD formats cannot do the job because:
-
Video resolution: The resolution of DVD is 480 horizontal lines of resolution (480i or 480p for progressive scan) compared to high definition’s 720 lines
of progressive scan (720p), 1080 lines of interlaced scan (1080i) or
progressive scan (1080p).
-
Data rate: The maximum data transfer for DVD is about 10
Mbps (million bits per second), while HDTV requires up to 25 Mbps.
There is simply not enough capacity and data rate to put an HDTV program on a recordable DVD format.
-
Data capacity: With the higher data rate demanded by HDTV, comes higher data capacity that is required to store all this high definition picture.
A new optical disc format has to be invented to record HDTV.
And in this realm, there are two extremes of possible solutions:
-
Reduce the data rate: One way of recording HDTV is to compress the
MPEG-2 digital video
information to a lower data rate (i.e., use less digital data). Since the type of compression we’re talking about is
lossy, picture quality will degrade somewhat
as the compression increases to lower the bit rate. The idea is to compress enough to decrease the bit rate to
data capacity levels supported by current technology, while trying to preserve the high definition picture quality to a reasonable standard.
-
Support the higher data rate and data capacity: Another way of recording HDTV is to record it at the higher data
rate required by HDTV, but use brand new technology that would support the higher data rate and higher data capacity. This allows the high definition signal to pass without
excessive compression, preserving the detail of the original high definition picture.
Unfortunately, the development of High Definition DVD had split into two
camps which in turn resulting in two different formats:
Each camp followed a different approach in terms of the two extremes we discussed above.
We will take each of these formats in turn.
Editor’s Note: On this web site, we use the term “High Definition-capable DVD” to generically refer to
either of two new high definition capable DVD formats: Blu-ray Disc or HD DVD. Blu-ray Disc Format
 The first
High Definition-capable DVD format announced was the Blu-ray Disc.
This format was developed outside of the DVD Forum, a body that
supports the successful DVD-Video format. It was formulated by a consortium of nine manufacturers called the “Blu-ray Disc Founders”.
These companies include Hitachi, LG Electronics, Matsushita Electric Industrial, Pioneer, Royal Philips Electronics, Samsung Electronics, Sharp, Sony, and Thomson.
The idea behind this format is to use a new blue-violet laser technology (hence its name), with a shorter wavelength of 405
nanometers (nm). This translates to a smaller laser beam width, so that the spot that represent a single bit
of data can be made smaller, taking up less real estate on the disc surface.
This means that more bits (or data) can be crammed onto the standard diameter 12-cm optical disc.
The data capacity is a maximum of 25 GB for a single-layered Blu-ray Disc, and
50 GB for a dual-layered Blu-ray Disc. Recording is made using phase-change technology, similar to that used in
rewriteable recordable DVD formats
(DVD-RW, DVD+RW, and DVD-RAM) and CD-RW.
MPEG-2 video compression is used.
To record the high bandwidth signal of HDTV, Blu-ray Disc format supports a data transfer rate of up to
40 Mbps.
With HDTV broadcast consuming about 25 Mbps, this is plenty fast to record HDTV.
A single-layered Blu-ray Disc can hold up to 2 hours of HDTV content, or 4 hours of Standard
Definition TV (SDTV, 480i).
If analog TV broadcast is recorded, up to 16 hours can be held at an average data rate of 3.8 Mbps.
For audio, Blu-ray Disc offers Dolby Digital at a data rate of
32 Kbps - 384 Kbps, or pulse
code modulation (PCM) at up to 2.3 Mbps using 16-bit, 20-bit, or 24-bit word lengths. Applications for the Blu-ray Disc format
include pre-recorded high definition movies, home HDTV
recording, and computer data storage. The Blu-ray Disc Founders began licensing this technology in February 2003.
Currently, support for Blu-ray Disc format includes:
-
Manufacturers: Hitachi, LG Electronics, Panasonic, Pioneer, Royal Philips Electronics, Samsung Electronics,
Sharp, Sony, Thomson, Mitsubishi Electric, Denon, Apple,
Dell, HP
-
For movies, the following studios support and
releases Blu-ray Disc movies: Sony Pictures, 20th Century
Fox, MGM, Disney/Buena Vista, Lions Gate Films,
Warner Brothers, Paramount Pictures
Editor's Note: Bold indicates exclusive support for
Blu-ray Disc format.
Sony BDP-S1 Blu-ray Disc
Reference Player ($1,000)
HD DVD Format
 Created by Toshiba in conjunction with NEC, the HD DVD format
is relatively new in comparison with the Blu-ray Disc format. The technical
specifications were completed in 2004, with much similarity
to that of the Blu-ray Disc format. HD DVD players were introduced
in 2006. Support for HD DVD format includes:
-
Manufacturers: Toshiba, Sanyo, NEC,
RCA, LG Electronics, HP, Acer,
Microsoft
-
Movie studios: Universal, Paramount Pictures, Warner Brothers
Editor's Note: Bold indicates exclusive support for
HD DVD format.
Editor's Note: The HD DVD format was originally
known as the Advanced Optical Disc (AOD).
The HD DVD format also uses blue laser technology with a 405 nm wavelength and uses a 12-cm optical disc.
In terms of data capacity, a single-layered read-only (pre-recorded) disc would hold 15 GB, while a
dual-layered disc doubles the capacity to 30 GB. So how can the HD DVD’s 15 GB data capacity compared with
Blu-ray Disc’s 25 GB still hold the same 2-hour movie in high definition?
The answer is higher compression of the video bitstream using MPEG-4 video
encoding. Optimized for handheld and wireless devices, MPEG-4 also
offers some additional optimizations over the current widespread MPEG-2 video
encoding, to allow for more efficient compression. In other words,
MPEG-4 may be able to encode the same video footage at the same quality as
MPEG-2, but use slightly less data.
The fundamental advantage of the HD DVD format over the competing
Blu-ray Disc format, according to Toshiba and NEC, is principally lower cost.
They claim lower costs in replicating pre-recorded movies, since existing DVD-Video fabrication plants can be retrofitted to produce software on the
HD DVD format. Basically, the HD DVD format is an evolution of the DVD-Video format to provide HDTV pre-recorded content and recording capabilities.
Even Toshiba has admitted that HD DVD as an interim and transitional format, with the
Blu-ray Disc format as the long-term solution.
Blu-ray
Disc vs. HD DVD
The table below compares the key parameters of the Blu-ray Disc and
HD DVD formats.
Key parameters of the Blu-ray Disc and HD DVD
formats
| |
Blu-ray
Disc |
HD DVD |
Data
Capacities
[GB] |
Single-Layer |
25 |
15 |
| Dual-Layer |
50 |
30 |
| Maximum
Recording Time, HDTV |
Single-Layer |
2
hours |
2
hours |
| Dual-Layer |
4
hours |
4
hours |
| Maximum
Data
Rate [Mbps] |
54 |
36 |
| Video
Encoding |
MPEG-4
AVC,
MPEG-2,
VC-1 |
MPEG-4
AVC,
MPEG-2,
VC-1 |
| Disc
Diameter [cm] |
12.0 |
12.0 |
| Track
Pitch [um] |
? |
0.40 |
| Laser
Wavelength [nm] |
405
(blue laser) |
405
(blue laser) |
| Video
Formats Supported |
HDTV
720p, 1080i, 1080p |
HDTV
720p, 1080i, 1080p |
Video
Update Rates
[frames per second, fps]
p=progressive, i=interlaced |
24p,
50i, 60i |
60i |
HDTV
Maximum Picture Resolution
[pixels, W x H] |
1920 x
1080 |
1920 x
1080 |
| Sound
Formats Supported |
5.1,
7.1 |
5.1,
7.1 |
| Surround
Sound Formats |
Dolby
Digital,
Dolby Digital Plus, Dolby TrueHD (lossless),
dts, dts HD (lossless) |
Dolby
Digital,
Dolby Digital Plus, Dolby TrueHD (lossless),
dts, dts HD (lossless) |
So which format will win? We believe it hinges on
two perspectives:
-
From a movie perspective, we believe it is all about
content. That is, which format will consumers find most of the
movies they want to view? Blu-ray Disc is supported by 8 of 9
major studios, while HD DVD is supported by only three.
(Currently, Universal is the only studio that releases exclusively to
the HD DVD format.) So chances are, consumers will want to go
with Blu-ray Disc if they had to choose one format.
-
From a computer data storage perspective, we believe
it is all about capacity. Here, Blu-ray Disc wins hands down
with 50 GB of capacity vs. 30 GB for HD DVD.
So...
We believe
that Blu-ray Disc format will win
the High Definition-capable DVD format war.
There, we said it. (And yes, you may quote us.)
Backwards
Compatibility with DVD-Video
With a High Definition-capable DVD format war, you may
decide to put off your upgrade to either Blu-ray Disc or HD DVD.
Understandably so. But you cannot help but wonder: is it still a good idea to invest in a
DVD-Video collection?
Absolutely. The new generation of Blu-ray Disc and HD DVD players will
playback existing DVD-Video movies. So continue to add to your wonderful DVD-Video collection without concern.
Furthermore, many of these new Blu-ray Disc and HD DVD players will upscale
the DVD-Video to near HDTV quality, so your DVD-Video will continue to look
good on HDTV. For those of you that simply cannot wait, you
can choose to buy a Blu-ray Disc player or an HD DVD player, or one of
each, or you can buy a dual-format player. These are becoming
available from Samsung and LG. For additional info:
Notation: Throughout this web site and in this article, we use 1 GB to mean 1,000,000,000
bytes. Likewise, 1 Mbps is 1,000,000 bits per second. These are not the computer usage where 1 Kilobyte = 1,024 bytes.
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