On 2012-01-25, Richard wrote:
I've been sent 4 tapes of BBC quad broadcasts, and the person who sent them says they are in HJ. Does anyone know when the BBC switched from H to HJ?
I do have the equations and quite possibly at least part of the history somewhere within the Motherlode. Pretty much everyone of the gurus on-list also has them, and probably even something unwritten beyond that as well. :)
But yet again, I think we could do better than that, relying on modern signal processing. Namely, I'm reasonably certain it is possible to auto-detect even this kind of analog coding, if you know your stuff. The general pattern would be to track the average, long term I and Q on-tape, then apply a bit of continuous time signal processing onto how they map to the primary axes of the H and HJ (also the rest of them, even quadraphonic?) decodings, and then to apply some hard discriminative statistics onto the typical image you would expect to get under each source model. I'm reasonably sure you could statistically separate the typical H and HJ variants from each other, semi-blindly, at the 95% percent level, at most in 45 seconds.
Since successfully finished the SQ & QS project, it's time i dealt with H/HJ once and for all.
I'd obviously like a carbon copy of everything you find, since this is one bitch of an interesting problem.
-- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-50-5756111, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
