All,
As the Pspatial Audio CD-4 decoder is being discussed here, I thought it was time to join the forum because I am responsible for the decoding algorithm development. Let me know if there are any questions I can (try to) answer.
There has been some discussion regarding the "soft fail" approach that I have taken. I do agree that (inevitably) this will sacrifice some degree of the strong directionality of CD-4. (I also know that it is this aspect which is so admired by quadraphonic fans.) Nevertheless, within the limitations of the Stereo Lab software program which is a "fire and forget" decode, I need to be sure that the decode will be be reasonably reliable. Because of this, I have to "play it safe" and aim to get a reasonable decode in most circumstances.
For the present, I'm not going to try to emulate the best CD-4 decode from the best hardware. I am assuming that the discs, and the associated hardware, may not be "tuned" to CD-4 performance. In this way, at least, Stereo Lab should complement a top-flight hardware system.
Kirk's point that we could offer a pure decode is a distinct possibility. In fact, it involves a lot more processing to take the approach I have. Straightforward emulation of a 1970s hardware decoder is absolutely possible. We can look at this at a later date if folks here are interested for us to do that.
May I make a request for any needle-drops of CD-4 material please. But there's a catch, I do need a 96kHz file UNEQUALISED. Post RIAA eq reduces the carrier signals too much. If anyone has the equipment to provide needle-drops of this type, I would be very grateful. I'm getting very bored of the few CD-4 discs that I have!
Best,
Richard Brice