NAD Technology Update
November 29, 2007
NAD Technology Update
HDMI 1.3 and the new Dolby and DTS Surround Sound Formats
As our industry evolves further into the 'digital domain' we often find both a knowledge gap and an expectation gap regarding forthcoming technology. The NAD Lab is working very closely with technology developers to be sure that our products remain at the forefront of technology, and we have some interesting news to report in this paper. NAD is strongly committed to providing important new technology as soon as it is available.
We get many questions about upgrading past or present products to include new features. In many cases these are features that have been announced in a press release but do not exist in commercial release.
As a general rule, new advanced features require more processor power and memory, and generally come with new copy protection and other restrictions on use. Furthermore, if these features are licensed there is usually an increase in cost associated with the feature. Per unit royalties on many digital AV products now represent >10% of the cost of the product! And this does not include fees manufacturers must pay for implementation and compliance testing.
HDMI Versions vs. Features
First of all, HDMI is just a pipe for content, it is not a feature! Whether it is 1.0, 1.1, 1.2, 1.2A, or 1.3 is really not important. What is important, directly relates to the features supported in any given product. For example, many of the new features supported by 1.3 are not yet available and may never be widely supported—even on products with HDMI 1.3 capability. Dolby True HD and 32 bit colour, for example, are potential features supported by HDMI 1.3. Device support for these features is the relevant question, not whether the component has a 1.3 chip or not. Finally, new versions are always backward compatible with previous versions so there is no need to worry about connecting equipment with different HDMI versions.
NAD, as part of our standard development regimen, has acquired the latest "up-to-the-minute" test equipment for evaluating HDMI and HDCP performance. We have tested a lot of currently available products, and while compatibility is getting better, many HDMI devices on the market today do not fully comply with HDMI standards or do not properly interpret HDMI and HDCP data. HDMI is a 2-way pipe for information, and if all the various components in the signal chain do not conform precisely, there can be, and probably will be, operational issues. Given the complexity of HDCP encryption this is not surprising (the certification test report is 300 pages of data!), but a factor of which we must all be aware. While digital video displays generally look best with a digital video signal, analogue video via Component Video interface is almost indistinguishable and is generally far more robust and reliable.
This is the current hot and generally misunderstood buzz word. With many flat panel displays (and a couple of front projectors) now supporting 1920 x 1080 (2,073,600) pixels, there is a rush to find new content to light up all the pixels.
1080i will also light up all the pixels, except in an interlaced or every-other-row of pixels mode. As long as this interlacing is refreshed often enough, the human eye cannot see the scan lines. This refresh rate has been carefully studied since the early days of the cinema and it has been determined that 24 frames of film per second exceeds the eyes ability to pick out individual frames and gives a smooth flicker-free image. For an interlaced video image to meet the same criteria it needs to be refreshed at least 48 times per second (with every frame scanned twice, this is called scan rate). Happily, our domestic broadcast standards, NTSC and PAL video systems use 60 and 50 times per second scan rates respectively, both exceeding the 24 fps detection threshold.
In order for the eye to perceive (the scientific term is visual acuity) 1920 x 1080 pixels you must either sit very close to the TV screen, or you need a very large screen! At a typical 10 foot (3 meter) viewing distance a 70 inch or larger screen would be required to resolve the visual benefit. Otherwise, your financial investment is wasted paying for extra display resolution.
There are also advantages and disadvantages to interlaced vs. progressively displayed images. Interlaced displays handle fast moving images better than progressive displays, while progressive displays offer better detail for static images. Interestingly, the concept of progressive scan originated in the computer industry where text on a progressive display is easier to read.
Finally there is the issue of 1080p sources. Right now the only source material for 1080p is DVD HD and Blu-ray, and the number of titles available is still very small. Satellite and cable do not offer any 1080p content at this time (and may never because of bandwidth limitations). Some DVD players can scale native 480 and 576 content up to 1080i or 1080p, but there is always a price to pay in terms of "conversion artifacts". In other words, you may end up with a poorer quality picture because a digital processor is filling in the missing pixels with "guesses" rather than actual data.
One final consideration; many HDMI cables are not designed for the extra bandwidth required for 1080p. HDMI 1.3 specs a cable as either 'Category 1' (74.25 MHz) or 'Category 2' (340 MHz). 1080p requires a bandwidth of 150 MHz and most cables are only certified to 74.25MHz, so don't be surprised if you need to upgrade cables to get 1080p sources to work reliably.
Dolby Digital Plus and True HD
Dolby Digital Plus is essentially Dolby Digital with a higher bit rate (variable from 320kbs to 6.14Mbs) and the ability to encode up to 14 channels of information (13.1). It is backward compatible with the current Dolby Digital which has 5.1 channels and a 384 kbps to 640 kbps bit rate, although on DVD it is limited to 448 kbps. As we have learned from MP3 and other "lossy" codecs, higher bit rates equal less compression and better sound. Most current DVDs do not offer the higher available bit rates. Discs with multiple soundtracks have to lower bit rates to fit them onto the DVD. We won't see DD+ or True HD being applied to standard DVD's, only to the new higher capacity disc formats.
While DD+ is mandatory for DVD HD and Blu-ray releases, Dolby True HD is optional. Dolby True HD is a "lossless" system utilizing MLP compression and has a data rate 16 Mbps and 8 channels.
DTS also has new products tailored to the new disc formats, but only standard DTS 2 channel is mandatory. As you step up the DTS product ladder 5.1 and ES 6.1 are added as well as 96/24. All these use a variable bit rate with 768 kbps typical and 1.5 Mbps possible.
Next is HD High Resolution Audio with 7.1 channels and 3.0 Mbps bit rate for DVD HD and 6 Mbps for Blu-ray. Advancing to the top of the DTS hierarchy is HD Master Audio, which is lossless and uses a bit rate of 18.0 Mbps for DVD HD and 24.5 Mbps for Blu-ray. DTS HD can be either High resolution audio or Master Audio at any of the many bit rates, but limited to the maximum allowed by Blu-ray and HD.
We are in the midst of a major evolution in home entertainment technology as digital video finally comes of age, and new disc formats and other content distribution technology become available. Going into this whirlpool of change it is not clear which formats will become dominant or how quickly the new formats will be adopted. It is anyone's guess which formats will become dominant, and if history repeats itself, it is very likely that not all new formats will succeed in the long term.
Investing in high quality components that include a clear upgrade path is the best way to enjoy new digital content available both now and in the future. Formats may come and go, but NAD's high performance and flexibility will provide satisfaction for many years to come.
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