HDMI or High Definition Multimedia Interface represents the natural progression for AV equipment. In the PC industry the switch to a digital interface between computer and monitor happened a long time ago when LCD panels became prevalent. However, the ongoing use of CRT for televisions meant that a digital to digital link between source and display was not possible, but now that LCD and plasma screens have become the norm, a digital link is the obvious choice.

HDMI is very similar to DVI except that it can carry digital audio as well as video. You may well find early HDTVs with a DVI port instead of an HDMI port – this won’t be a problem as converters are easy to come by, but you will need to connect the audio separately. HDMI can carry up to eight channels of uncompressed digital audio, but to make use of that multi-channel goodness you’ll have to be sending the signal to a surround sound amplifier. That said, if you’re serious about your home cinema you’ll want to hook all your source devices to an amp, and then run a single monitor cable to your TV.


A cable with HDMI at one end and DVI at the other.


Another advantage that HDMI has over DVI is the size of the connector. An HDMI connector is tiny compared to DVI and it also just plugs straight in rather than having screws on either side. Also it can be all too easy to bend the pins inside a DVI plug whereas an HDMI plug is far more robust.

An HDMI port is only half the story though, both your source device and your TV must be HDCP (High-bandwidth Digital Content Protection) compatible. HDCP is Hollywood’s safeguard against high definition piracy. With a digital interface like HDMI, the last thing that Hollywood studios want is for you to be able to make perfect digital copies of its high definition movies. HDCP stops digital copies from being made by encrypting the data stream that travels between source and display, and making sure that both devices are allowed to talk to each other.

Both Blu-ray and HD DVD players will have Ethernet ports, which allow the player to communicate with the manufacturer and movie studios. Software can demand that a player is online before the movie is played and if the studio recognises the player as being compromised as far as copy protection goes, it can revoke the player’s licence to play the content. The subject of your movie player constantly communicating with third parties and logging your viewing habits is somewhat concerning and something that I will cover in greater depth in my future Blu-ray and HD DVD feature.


The HDMI conector is smaller and more robust than DVI.


If an HDCP enabled source device recognises that the display it’s connected to isn’t HDCP compliant it may choose to either downgrade the resolution of the video (thus negating the point of HD) or even not show the video at all. Thankfully it’s pretty hard to find an HDTV that isn’t HDCP compatible these days.

Just to confuse matters, the HDMI 1.3 standard was recently announced and should be appearing on devices towards the end of the year. The new standard significantly increases the available bandwidth, thus enabling more detail (both visually and audibly) to be sent down the cable. Does this mean that you shouldn’t buy any equipment that’s using the current HDMI 1.1 standard? Probably not – one thing I’ve learned from working in the technology industry for so long is that there is always something better coming down the line, but you can’t sit on the fence forever.

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