format for CD (1 Viewer)

[Bill Polley]

what are the differences between DVD-A and SACD, and how does HDCD fit in? I ask because I just realized that the Rotel 1066 offers HDCD decoding. I take it the HDCD signal is digital 2 channel while the others are 5.1 channel outputted to 6 discrete analog channels. Am I right? Also, are these formats at all compatible? Thanks

 

[Thomas Newton]

HDCD claims to offer 20-bit resolution in a backwards compatible way using regular CDs. Count me as a skeptic, particularly if HDCD is taking its bits from the part of the stream reserved for audio.

DVD-Audio and Super Audio CD are new formats that offer higher resolution, but that are encumbered by DRM.

DVD-Audio uses multi-channel PCM (compressed in a lossless way using Meridian Lossless Packing) at sampling rates of up to 192 KHz and sample sizes of up to 24 bits. This can be seen as a followon to 44.1 KHz / 16-bit PCM on CDs.

Super Audio CD uses a different technique entirely, where there is a really huge "sampling rate", but each sample is just a single bit saying "nudge the voltage up a tiny bit" or "nudge the voltage down a tiny bit".

DVD-Audio discs are not compatible with CD players. They can contain DVD-Video tracks for backwards compatibility with DVD-Video-only players.

Super Audio CD discs can be SACD-only, or can hold a SACD layer and a CD layer (for backwards compatibility with CD and DVD-Video players).

The "technological protection" on DVD-Audio is plenty strong enough to interfere with legitimate copying, but if it's like the one on DVD-Video, it won't slow down commercial pirate plants. The system on Super Audio CD takes advantage of characteristics that are unique to each pressing plant, and commercial pirate plants that bit-copy Super Audio CDs will be in for a nasty surprise.

Another difference: DVD-Audio uses audible watermarking, which has the conflicting goals of being inaudible, and of being able to survive MP3 compresssion. One editorial compared this to "protecting" a crystal clear pool of fresh drinking water by taking a leak in it. The Super Audio CD system can use similar in-band schemes, but I think people have said that the SACD discs released to date do not.