HDMI promises both high definition video and audio. But don't be fooled, HDMI does no

[Gregg Lengling]

We are just starting to see new high-end HDTV's, DVD players, and audio products including HDMI (High Definition Multimedia Interface) connectivity.  HDMI, which was conceived as the successor to DVI, for the passage of digital video signals also has the capability to carry uncompressed digital audio and video signals together through the use of one cable and connector.   This means that it has the potential to bypass all other digital audio connectors including coax and optical (TosLink) and 1394.  Wow!  The implications are staggering.  With 5.1 HDMI included in A/V Receivers, DVD players/recorders (including future Blu-ray and HD DVD players), Satellite Receivers and Cable HD Receivers, it eliminates the need for digital audio – coax and optical – and 1394 entirely to carry digital audio signals.  It also makes it easy for the consumer to attach one cable instead of several from their Satellite/Cable HD Receiver, and DVD player to A/V Receiver to TV.

 

However, I was very troubled at the recent C.E.D.I.A. Expo to find out that one has to be careful about HDMI these days.  Why do I say this?  Both Audio and Video products currently on the market that utilize HDMI only passes 2.0 digital audio, and not full-blown 5.1 surround sound audio.  These products include A/V Receivers, DVD players/recorders, and HDTV's.    Of course, to be fair, Silicon Image – the creator of HDMI -- claims that it can do 5.1 audio easily.  However, the hard fact is that none of the connections currently on the market today are passing 5.1 audio!  In an ideal world, HDMI has the capability to carry all HD video and digital audio signals including Dolby Digital, DTS, DVD-Audio and SACD via one connector plus full-blown HDTV and HD-DVD signals as well.  This is a terrific scenario as is anything that will cut down on cabling clutter is a great thing.  The back of my home theater looks like hundreds of strands of spaghetti wires.

 

I'm just warning caution right now, and making you aware of the limitation of current products in the marketplace.  We haven't eliminated everything just yet, and you should be aware of it.  Clearly, it will take time for the audio companies to include full-blown HDMI switching capability as it took several years for component video switching to become commonplace.  Today, several manufacturers now include component video switching with up conversion (from composite and S-Video) on numerous models, which is pretty neat.    

 

Several upscale HDTV's now include HDMI input(s), and a handful of DVD players include HDMI output.  Sending both digital audio and video signals directly to the TV via HDMI does simplify matters up converting those already pristine DVD images to near HD quality.  Audio, on the other hand, from that DVD player will only be sent at Dolby Digital 2.0 quality to be handled by the TV's internal audio system.  And, if you're using the TV's speakers and Dolby Digital processing, you won't know the difference.  

 However, if you thought that by sending those audio signals via HDMI to an A/V Receiver using HDMI inputs, it would process full-blown Dolby Digital and DTS, you'd be mistaken.  Today, those products only pass/receive Dolby Digital 2.0 audio.  To obtain full-blown surround sound, you would have to use either the digital audio connectors or 1394 (if available) from your DVD player or Satellite Receiver.  Of course, to obtain the best digital video and digital audio signals overall, you would simply send video HDMI signals to the display directly, and digital audio signals directly to the A/V Receiver or Processor using the digital audio connectors of both products.  You've lost the ease-of-use switching capability, but retained pristine signals.

 

Going forward, 2005 versions of satellite and cable HD Receivers may include 5.1 audio HDMI capabilities.   You will have to double-check to make sure.  Within the audio community, HDMI switching capability will follow later in 2005 and 2006.  Ultimately, it can be expected from all of the major brands.  Initially, HDMI switching capability will only be available on a handful of high-end audio products.   In turn, those audio manufacturers that started including HDMI will follow with HDMI up conversion from all other video sources.  Presently, only two audio manufacturers have announced A/V Receiver products with true 5.1 audio HDMI switching capabilities – Denon and Pioneer -- that will reach market early next year;  although, it should be noted that both models are quite pricey costing several thousand dollars.

 

Going in a different direction, other companies like Harman and Yamaha, for example, are including Faroudja circuitry to enhance standard definition video signals from their A/V Receivers.  Denon has just announced the inclusion of Silicon Optix's Realta HQV video enhancement chip on their new DVD-5910 universal DVD player utilizing HDMI output.  Will it pass 5.1 audio?  We're not sure as it won't be available until next year.  While it's not totally clear if TV manufacturers will start including 5.1 HDMI capability with 2005/2006 sets, they will start adding multiple HDMI inputs to accommodate numerous video products with HDMI outputs.  TV companies like Hitachi and Toshiba have already started adding multiple HDMI inputs on the backs of the top-end HDTV's.

 

So, for the time being  if you are passing digital audio from your DVD Player or Satellite Receiver, I suggest that you use the either the digital coax or digital optical output found on the back of the product.  The bottom line -- potential buyers of new DVD and audio products with HDMI capability will have to ascertain if it passes 2.0 digital audio or truly 5.1 digital audio.  It could be years before true 5.1 HDMI reaches the masses.  Digital audio and 1394 are here today, and are proven technologies that can pass all types of digital audio signals.  These are the connectors of choice to pass all types of stereo and surround sound.  As an aside, 1394 will also pass HD signals from a display device to a recording device retaining pristine image quality.