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Re: sbm magic...

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graemme

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In Reply to: sbm magic... posted by david elias on October 21, 2003 at 17:01:55:

Hi David and Eric,
It isn't a 'given' that the redbook layer will be derived from the DSD 2 ch master. This is an artistic/economic decision that someone needs to make.
I much prefer the sound of standard redbook CD audio converted from the DSD 'source', *EVEN* if that 'source' was originally 20/24 bit 44k1 (and higher sr) PCM.
Sony's 'SBM Direct' and the Philips 'Audio Format Converter' get the downsampling math *very* right... ;->
Regards,
Graemme

Follow Ups:

Re: sbm magic... thanks for the clarification Graemme - David Elias 22:20:12 10/21/03 (4)
I agree, the SBM math sounds very right! - Regards, David
- Does SBM work at higher bitrates? - Eric LeRouge 01:17:23 10/22/03 (3)
  Is it possible to use SBM to translate "pure" DSD bitstream to 24/96 for example? (and has anyone tried it?)
  I'm asking this, because if a careful remaster has been done in DSD, maybe it's more efficient (from a time and money perspective) to use it for an alternate PCM release, rather than going back to the original material
  (of course, this is not a purist point of view, but if it works, why not?)
  Best
  Eric
  PS: I think it's cool that you guys can talk and communicate on this forum
  - Re: Does SBM work at higher bitrates? - graemme 10:18:30 10/22/03 (0)
    Hi Eric,
    I'm not familiar with the inner workings of the Sony SBM Direct process to know if it could support PCM rates outside of direct integer relationships. The implemtation of it in the Sonoma workstation seems to be specifically for DSD to Redbook conversion, which it does very nicely!
    The PCM output of the Meitner DSD AD is a realtime downsample of the DSD AD conversion, via the Sony 'E-Chip' to 24 or 16 bit at 44k1. I use this for a backup to the DSD recording chain and it sounds great, for what it is.
    The Philips 'Audio Format Converter' software definitely converts DSD to *any* of the standard PCM sampling rates/wordlengths. A DSD to 24/96 conversion is done by multiplying the DSD rate x5 and then dividing by 147 to reach 96K.
    This tool can also convert PCM to DSD (from any rate/wordlength) as well.
    I agree with you about 'mastering once' and delivering on multiple formats - makes a lot of sense to me (and it's how I like to work.)
    Regards,
    Graemme
  - of course something similar could work... - tunenut 10:01:59 10/22/03 (1)
    SBM is essentially a marketing term for a proprietary form of sample rate conversion...and the final PCM tracks have been noise shaped in some way that is supposed to be psychoacoustically optimal...that is probably the proprietary part, not the simple math to do frequency rate conversion. Same type of thing could be put together to accomplish any type of sample rate conversion, although the exact details of the noise shaping would differ.
    - Re: of course something similar could work... - graemme 17:57:38 10/22/03 (0)
      Hi there,
      'Super Bit Mapping' is specifically the noise-shaped dither part of the process, which has been around (and was occasionally updated) for a while in the PCM world.
      'SBM Direct' adds the conversion from DSD to PCM to the above scenario.
      The main point (for me, anyway) is that the two implementations I mentioned do a better job of converting PCM (20/24 bit 44k1/88k2) to PCM (redbook) via DSD than most available word length reduction systems that are 'just' converting from PCM to PCM without the intermediary step.
      Try it...
      Regards,
      Graemme

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