HDTV retailers use a well known technique in which is to boost the brightness in their stores as well as the HDTV’s themselves to entice buyers. Why? In part because bright screens can mask poor black-level performance on cheaper sets. But then some buyers are then surprised when sets that “pop” in a store appear far more muted when they are hooked up in the living room.

A recent study by HD Guru measured 10 homes with light levels that ranged from 1.2 to 110.1 lux, the stores tested visited measured: Best Buy, 180.3; Sears, 236.58; Target, 371.38; Walmart, 411.66; BJs, 412.13, and Costco, 742.77. You’ll notice that the stores that have sales people who specialize in home theater equipment (Best Buy and Sears) register far lower readings than the big-box and warehouse stores that don’t offer dedicated TV help. HDGuru theorizes that the amped-up levels at Target and Costco help the cheaper sets they sell look a lot better than their performance will be once you bring them home.

Of course, all stores will be more brightly lit than a typical home, but that doesn’t mean the TV department has to be as bright as the rest of the store. In fact, HDGuru’s measurement of the Magnolia Home Theater section of the Best Buy found a far more muted reading of 34.7 lux, like in a typical living room. Why the difference? The more expensive sets sold in the Magnolia showroom have superior black-level performance that can’t be properly displayed with the cheaper sets radiating in the other part of the store.

The conclusion based on this report, Don’t expect the HDTV you buy from  retailers will have the same picture as it displayed in the store.

HDMI Cable Connectors

There are basically two types of  HDMI cable interconnects: a compact Type-A 19 pin connector, and a slightly bigger  29-pin Type-B HDMI connector. This second connector allows for the use of dual-link HDMI configuration, which doubles the maximum transfer rate that can be used, up to a maximum pixel clock rate of 330Mhz.

Important Note(s):

Transmitting devices with a Type-A HDMI connector can be connected to receiving devices with a Type-B plug using an HDMI cable with a Type-A plug at one end and a Type-B plug at the other. It is not possible to connect a transmitting device with a Type-B plug to a receiving device with a Type-A plug. Further more, as already mentioned earlier on, HDMI and DVI-D enabled devices can be interconnected through the use of a DVI-D to HDMI cable converter for both single-link and dual-link applications.

This means that in addition to standard straight Type-A to Type-A, and Type-B to Type-B HDMI cables,  you can also come across three other different types of HDMI cable connectors:

• DVI to HDMI Cable adapter with single-link DVI-D connector on one end and HDMI Type-A connector on the other.
• DVI to HDMI Cable adapter with dual-link DVI-D connector on one end and HDMI Type-B connector on the other.
• HDMI to HDMI cable adapter with a Type-A connector on one end and a Type-B connector on the other.

In conclusion, keep in mind that if you are connecting a DVI-enabled devices do not support HDCP, then connecting your DVI gear to an HDMI port will force the HDMI-enabled device to downgrade high definition video content to standard resolution.

How does HDMI transport digital video and audio over the same HDMI Cable?

We will not go into the actual architecture of how this is done, yet there are a few basics worth knowing about how HDMI transport data and in particular, how this transport mechanism relates to the maximum data throughput or bandwidth, that can be carried over an HDMI cable connection.

HDMI uses the same unique TMDS encoding protocol used in DVI, to transport video and audio information over the same interconnect. TMDS stands for Transition Minimized Differential Signaling; it conveys data by transitioning between ‘on’ and ‘off’ states while utilizing an advanced encoding algorithm to minimize the transitions necessary to transport data between the HDMI ’source’ e.g. an HDMI-enabled digital satellite TV set-top box, and an HDMI-enabled ’sink’ or monitor e.g. a digital television.

Minimizing the required transitions avoids excessive electromagnetic interference (EMI) levels on the interconnecting HDMI cable. At the same time, additional operation is performed to minimize long strings of ‘1′ and ‘0′ which otherwise can cause detection errors. In this process, incoming 8-bit data is encoded into a 10-bit transition-minimized, DC-balanced word.

The HDMI standard specifies both single-link and dual-link HDMI. A single HDMI link is made up of 3 TMDS data channels using three separate differential pairs on the HDMI cable to transport audio and video data at a maximum pixel clock rate of 165MHz; this is equivalent to 165 million pixels per second. A fourth differential pair, called the TMDS Clock provides the pixel clock for timing the data stream.

Single-link HDMI is fully compatible with single-link DVI-D while dual-link HDMI is compatible with dual-link DVI-D.

Video Transport: Video information is transmitted as a series of 24-bit pixels – 8 bits each for each of the primary colors; these are encoded using the TMDS protocol into three 10-bit words per pixel clock period (i.e. each pixel is made up of 30bits). This means that the effective maximum data throughput  is 4.95Gbps (165MHz x 30-bits) over a single-link HDMI cable, or 9.9Gbps over a dual-link HDMI interconnect; these rates determine the maximum video signal resolution that can be transmitted over single-link and dual-link HDMI cables.

Considering that a single-link HDMI can transfer up to 165 million pixels per second, it is clear that HDMI has more than enough bandwidth on a single link to accommodate even the highest HDTV format available today for consumer electronic products. In the case of a dual-link mode, an HDMI cable connection can handle a bandwidth of up to 330Mhz.

Audio Transport: Audio can be from two to eight channels, using sample rates up to 192KHz. Multi-channel digital audio is time multiplexed into the same  TMDS data streams used for video; this is possible as audio requires a much lower data (max. 192Kbps), and therefore, it can be easily ’stuffed’ in between empty spaces available on the data channels.

The HDMI standard also includes two other important channels – these are the DDC and the CEC.

DDC – Display Data Channel, is used to enable the source device to interrogate the receiving device about its configuration and capabilities. This is done by reading the E-EDID (Enhanced Extended Display Identification Data) data from the receiving device. Data is transferred using I ² C signaling with a 100kHz clock.

CEC – Consumer Electronics Control Channel, is optional and allows the control of several audiovisual devices that the user might have. It is mainly used for remote control functions. It uses the industry standard AV Link protocol transmitted over a one-wire bi-directional serial bus.

PARADIGM, Monster, Belkin  and SimplayHD are some of the more common brands of HDMI cables. Cables can be purchased from a variety of different sources such as major brick and mortar retailers (Bestbuy) or through online retailer such as Amazon.com.

When it comes to buying HDMI cables you basically are paying for brand, materials in the construction of the cable, packaging and of course percentage profit for the retailer.   A $10 cable is likely to perform just as well as its $50 counterpart for basic viewing of dvd movies or limited applications, however when it comes to Blu-Ray or high speed applications in whcih there is considerable amounts of data being transmitted then the $5 cable will NOT PERFORM as well as the $50 counterpart.

There is an old addage “You pay for what you get” and we are firm believers in such a philosophy.  There is no doubt that major brand manufacturers are adding huge margins associated with their products, take for example: PAR-A-DIGM HDMI Cables….when compared with most other non-branded hdmi cables they are expensive however when compared with other branded hdmi cables they are competitively priced.  Also during performance tests against other non-branded or cheaply priced cables for high speed data use such as the Blu-ray movies…the cheaper cables performed very poorly and considerable lag was noticed during the movie.

Even through price doesn’t need to be a factor when purchasing your HDMI cable, you will want to consider cable length. Signal strength deteriorates over long cable runs, with approximately 33 feet being the recommended maximum cable length. Keep this in mind when deciding on your equipment setup.  A good quality constructed hdmi cable provides excellent signal shielding and minimal RFI/EMI Interference thus resulting in superior performance, and cheaply priced hdmi cable often times have inadequate shielding resulting in signal loss and poorer image quality.

The basic question should be asked?

If Iam purchasing expensive HD and AV equipment…should I not use quality constructed hdmi cables to connect my devices together to achieve the best results.  Why would I choose cheaply priced hdmi cables…..it makes no sense.

What is the difference between HDMI and DVI ?

Both are closely related to each other in that HDMI and DVI both use the same digital encoding scheme used by DVI-D in the transport of digital video signal.

This further supports how normal DVI devices can be connected to HDMI devices by simply using an DVI to HDMI Cable Adapter, however in this case the digital audio will have to be transferred separately since DVI does not support audio over the same cable interconnect.  This is not the case with a HDMI to HDMI cable connection in which the audio signal is carried along with the digital video signal over the same cable interconnect.

Another major difference between HDMI and DVI is that HDMI does not have multiple configuration standards like DVI — DVI-A, DVI-D, DVI-I, DVI-Dual link, etc.  The HDMI Connection simplifies the connection by providing one standard connection type with all HDMI compatible devices.  The fact that HDMI is equivalent to DVI-I imples that HDMI is limited to that format only and that there is no way to adapt an analog VGA signal through a HDMI connection which is common using a DVI connection interface.

Other important differences include the following:

• HDMI interconnects are substantially smaller than the 37.0mm wide DVI plug
• The DVI Standard was originally developed to be used by PCs, while the HDMI Standard was developed by major electronic mfg to be used specifically in consumer electronic devices such as DVD players and digital TVs

Welcome everyone!

This Blog is dedicated to reviewing the basic and not so basic requirements in selecting the appropriate hdmi cables for whatever the intended use may be.

There are many factors to be reviewed when trying to select the correct hdmi cables and our goal is to help you filter through this information and select the correct hdmi cables based on your individual needs or requirements.

Our experts have extensively reviewed the marketplace and tested various manufacturers of hdmi cables and based on this have formed an opinion…..however you may choose to disagree with this opinion and we respect that decision as well.