Smart Home Pro

Just what are the differences between "digital" signals and "analog" signals? (And why do I care?)

If you're curious to learn something about analog and digital video and audio, read on.   This could get just a little technical, so be forewarned.

We know the future lies in digital audio and video.  The process started over two decades ago with the introduction of the Compact Disc (CD) audio recording format.  Vinyl albums are analog and CDs are digital.   Video made the change from VHS tapes (analog) to DVDs (digital).  Most folks will recognize the improvement in sound and video quality associated with these changes.  (This is the why do I care? answer – the quality is better!)

Moving signals among your components was largely analog until the advent of digital audio and HDMI (High Definition Multimedia Interface).  The outputs from your newer CD player and DVD or Blu-Ray player can now be sent to your amplifier or TV using digital signals.   Remember the simple RCA white and red cables for audio, and yellow RCA plug for video?   These are all analog signals, and they're being replaced by digital signals in the new days of content protection.  I'll have another article on content protection in the future.

Analog signals are quite simple.  In a perfect world, a signal (waveform) inserted into one end of a wire looks the same at the far end of the wire.  Being far from perfect though, the signal at the far end of the wire is "noisy" and has lost some "oomph."  This means the signal has lost some intensity, as well as some of its shape.   There's little to be done about this loss.  Good quality cable installed properly is important.  But once gone, the signal is gone.

Digital signals follow the same rules of transmission signal loss.  But the signal is a series of "0" (off) and "1" (on) values.  As long as there's enough of a signal left at the end of the wire to accurately decipher a "0" from a "1," the signal sent is identical to the signal received.  Your equipment then reconstructs the digital signal into your sound and video.

The conversion of sound and video into digital signals and back is way beyond the scope of this entry.  Special processors – computers, really – create the digital signals and know how to decode them on the receiving end.  But the quality of the encoding scheme and the type of cabling does matter in the custom integration business.

Quality of Encoding

Digital video is relatively new.  Digital audio is more familiar, and in this area are terms such as DTS, MPEG, THX etc.  The acronyms seem endless.

Digital data uses a LOT of space on a computer disk, or takes a LOT of bandwidth over a wire.   So the mathematicians create ways to squeeze digital information into a smaller space, or over a smaller wire, using data compression.  Suffice it to say data compression has its place, but for the best sound and video, we prefer to avoid compression if at all possible, simply because some quality is often lost on the receiving end after decompression.

Cabling Requirements

At the risk of loosing some readers, let me list some of the more frequent terms and acronyms used in the industry, and their association with analog or digital.

Component Video – Analog video technology, using three wires (YPbPr).  Good for resolutions up to 1080i.

Composite Video – Analog video technology, using a single (usually coaxial) wire.  Good for resolutions up to 480i.

HDMI – Digital video and audio technology, using a specialized cable.  Good for resolutions up to 1080p with Deep Color –the current state of the art – and beyond.

DVI - Digital video and technology, a precursor to HDMI.  Electrically equivalent to HDMI and capable of the same resolutions.  But note: NO AUDIO.

DisplayPort – Digital video and audio technology, primarily seen on computers so far.  Audio is OPTIONAL, but better audio support appears with HDMI for the moment.

Most of these use different types of cabling.  Smart Home Pro will pick the best option for your needs and wishes.   If we could, we'd just install HDMI cables everywhere and be done with it.   But HDMI signals can't travel very far and they're expensive.  We can solve this, but that's a different article.

Many clients are very happy with Component Video distribution, as it provides 1080i High Definition video over reasonable distances, at a reasonable cost.  Videophiles demanding 1080p or greater resolutions, distributed throughout a building will need one of several more specialized solutions.

If you have more questions on this topic, call or stop by the Smart Home Pro showroom and we'll be glad to take your questions.