Since when has this been such a problem? Connect the video, connect the audio, add some RF and scan the box. Once it’s all done you should have some pretty stunning images – right? Well sort of.
Remember, system design is a fundamental link in the sales process and by posing a few simple questions to your client you will ensure that you deliver a great image in a system that’s simple to operate.
First, let’s look at the various connection methods in ascending order of performance.
Analogue
RF: If you hook up a DSTB with RF (modulated audio and video) to a flat panel display, you might want to consider a new career path. This is the lowest form of video distribution and can only be used if the panel has an in-built tuner.
Composite video: Also referred to as CV or ‘comp’, this is baseband video in its simplest form.
S-Video: The next step up the video food chain uses the four pin mini DIN connector. It offers better performance than composite and is sometimes called YC (Y= luminance, C= chrominance).
Component: Probably the most common connection method which used the red, green and blue RCA connectors. Also known as YUV/Y, Pb, Pr, this system offers great compatibility with other devices and switching systems.
RGBHV: Similar to component but with two extra connections which carry horizontal and vertical sync information. RCA connectors are sometimes used but mostly HD15 connectors.
Digital
DVI: Digital Video Interface was introduced into set top boxes approximately two years ago and is now common on most HD STBs. DVI provides uncompressed digital video information at high resolutions. There are four types of DVI connectors with the most common being DVI-I (integrated analogue and digital).
HDMI: High Definition Multimedia Interface is the latest form of digital connection that also incorporates eight channels of audio plus control information in the one cable. Some DSTB’s support this connection method as do display devices and AV receivers.
So what’s the best? Well, that depends on what else you have in the system. Good system design is not just about connecting the devices with the latest and greatest cable, it’s also about providing a simple to use solution for the client. Unfortunately, not many people appreciate that having less often means achieving more.
When designing a system consider the other items that the client may own and how these need to be integrated into the system. If their one-year-old LCD display has a DVI input, the DVD player has a component and DVI outputs and the DSTB has all of these plus HDMI, then the client could potentially need to switch the LCD panel to three different inputs for the three sources. Add an AV receiver to look after the audio and then the switching has just turned into a six-button operation.
Here’s a tip
Use the highest possible connection method that’s common to all sources and displays – 90% of the time this will be the component (YUV/Y, Pb, Pr) option.
Will it provide you with the best possible image? The short answer is no but I’m sure that your client would much prefer to simply turn their display onto one input rather than switch it every time they decide to change sources; and the image is still impressive. Component will still pass HD video up to 1080i with great results.
I’m the first to admit that the digital signal path will provide a better image as there is no digital to analog conversion. AV receivers are now available with HDMI switching and if you have a suite of products with HDMI outputs plus a display with an HDMI input, you can complete a truly digital signal path. My experience with HDMI has led me to think that not all HDMI equipped products are the same. In fact, there are some considerable differences in audio level outputs. I still prefer to use S/PDIF as it’s generally consistent from product to product and is easy to manage.
HDMI also has some distance limitations although this can be overcome with some active (powered) line drivers which will allow you to use HDMI links over 40m. The same can also be said for DVI.
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