On 30 April 2013 11:06, TON Eichinger <[email protected]> wrote:
> Am 30.04.2013 11:39, schrieb Dave Malham: > >> I used Telecom C4 a couple of times but much preferred the sound of Dolby >> > > I am quite sure Telcom companding is independent in each frequency band, > not ganged. > Indeed they were but as the bands were much wider than our hearing's critical bands you couldn't rely on masking to hide the artefacts inside the individual bands as you can on modern digital systems with their high band counts. Please not that this is NOT an argument for the perfection of MP3 :-) This meant you got more >> noise reduction but also more artefacts, though not as much as DBX which >> used neither sidechain nor bands. Dolby A, because of its sidechains had >> to >> be aligned to within half a dB of the correct level or the process went >> wrong because the compression thresholds went out but neither C4 nor DBX >> needed anything other than aligning to optimise machine dynamic range as >> they had no thresholds. This would seem to make Dolby A more difficult to >> use but as every Dolby A unit incorporated a proper Dolby Tone generator >> which produced a unique warbling test tone that all Dolby A tapes should >> have on them, this shouldn't be a problem. >> > > The last point is the most critical, and although mandatory, some tapes do > not have any tones on them. Yep, true - that was one of the things my students would get serious shouting at (and loss of marks) for not doing back in the day. Moreover, once the tapes are in the digital domain, the reference to > magnetic levels might get lost and proper adjustment to half a dB for > correct decoding will be impossible. > Very true - whilst I (and most practising engineers) could, if the tone(s) were lost, adjust by ear to some extent in the days when we were using Dolby A on a daily basis (and provided we knew the music and so on) it was rather hit and miss. Even if my ears were as good now as they were 3 decades ago there's no way I would stand a chance of getting it anywhere near these days :-( When Dolby tones existed on tape and have been transferred, the software > would need metering and adjustment, > Fortunately this could easily be automated in the digital domain Dave > > > ______________________________**_________________ > Sursound mailing list > [email protected] > https://mail.music.vt.edu/**mailman/listinfo/sursound<https://mail.music.vt.edu/mailman/listinfo/sursound> > -- As of 1st October 2012, I have retired from the University, so this disclaimer is redundant.... These are my own views and may or may not be shared by my employer Dave Malham Ex-Music Research Centre Department of Music The University of York Heslington York YO10 5DD UK 'Ambisonics - Component Imaging for Audio' -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130430/fd8da734/attachment.html> _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
