Audio News for May 24, 2006

by | May 24, 2006 | Audio News | 0 comments

Hi-Def Video and Multichannel Audio Complexities – Any reader who has delved even slightly into high end video has probably realized that the complexities and confusions abounding in the field make audio seem simple and straightforward in comparison.  Rodolfo La Maestra, Senior Technical Director of HDTV Magazine, has observed that today’s video technology as implemented has completely overwhelmed regular consumers due to its complexity.

Prior to HDTV it was already confusing enough: going from a basic RF video cable to the three options of composite, component or S-video connections; properly decoding Dolby Digital and DTS in all their various versions; setting up 5.1, 6.1 or 7.1 home theater speaker systems with subwoofers on top of it; the complications of switching the video with the audio sources or keeping them separate, and so on.  HDTV added another new level of confusion, but now we are moving into the new hi-def/hi-res DVD formats, so be prepared for massive AV chaos!

Both of the battling hi-def DVD format camps have approved multiple technologies for  multichannel audio standards on the new discs. Dolby has Dolby Digital Plus, MLP Lossless and Dolby TrueHD. DTS has DTS Digital Surround, DTS-ES, DTS 96/24 and DTS-HD Master Audio – the latter being their lossless format. Most of the codecs offer up to eight channels. And most will be optional on the new discs; for example the only mandatory codecs for Blu-ray will be legacy DD 5.1 and DTS 5.1 – and only one or the other of them must be offered. The lossless codecs require an immense amount of space on the DVDs compared to the lossy formats. Some might even exceed the 50GB which is the Blu-ray maximum. So what if the particular studio wants to offer both DTS and Dolby lossless audio on a blockbuster movie? There is even an optional Blu-ray 6-channel uncompressed PCM at 192K/24-bit, running at 27.6Mbps.  Imagine how that eats up the space. There simply won’t be room.  And if the lossless codecs always sound identical to the source – as is constantly stated – why is it on DVD-As offering both PCM stereo and MLP stereo, the PCM option often sounds better? What’s wrong with SACD? The first Sony Blu-ray player won’t even play SACDs, amazingly.

The early hi-def players are expected to mix the audio internally, so they will no longer output an audio bitstream as was typical with standard DVD players. Consumers will therefore no longer be sure that a particular player will work with a particular AV preamp or receiver. HDMI or IEEE 1394 (FireWire) are becoming the standard for next generation single-cable connections. They deliver up to eight channels of 96K/24-bit PCM audio along with the video. Another possibility is the six-channel analog cable connection which we are currently using for SACD and DVD-A playback. If your AV processor/receiver lacks both the HDMI and multichannel analog inputs, you will have to use the S/PDIF connection and be limited to legacy DD and DTS 5.1, except that if the HD disc features a higher-bit-rate version of Dolby Digital, your processor will be running at a higher rate than with standard DVDs, resulting in improved audio quality.

Other considerations on the audio side of HD include the frequent upgrades of HDMI cable versions. V. 1.1 has now been superceded by v. 1.3, which is able to stream both the mandatory and optional audio codecs to a 1.3-equipped preamp/receiver, which would do the decoding and bass management. But of course both components would have to feature matching 1.3 outputs/inputs. Another new complication is that the HD discs are expected to support the streaming of bonus audio content – such as the director’s commentary during the movie – from the Internet. This would have to be internally mixed with the other audio components of the soundtrack, and requires an Internet connection!

Tech Director La Maestra’s reaction to all this is “How many more multichannel audio formats does a consumer need?” 

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