Subject: Re: [linux-audio-dev] pbd's votes on LADSPA
From: James McCartney (asynth_AT_io.com)
Date: Mon Mar 27 2000 - 04:16:11 EEST
on 3/26/00 5:57 PM, Paul Barton-Davis at pbd_AT_Op.Net wrote:
> In message <B503AAA3.A10%asynth_AT_io.com>you write:
>> on 3/26/00 11:12 AM, Paul Barton-Davis at pbd_AT_Op.Net wrote:
>>
>>> The [-1,+1] idea is abhorent to me, if
>>> only for the reason that it *guarantees* that we can't satisfy in-bits
>>> = out-bits.
>>
>> ?
>> It shouldn't. Scaling by 2^16 or 2^24 will only change the exponent, not the
>> bits in the mantissa.
>
> Eh ? Who says the scaling factor is 2^16 or 2^24 ? Its close, but not
> quite. This is particularly true if you have h/w which generates
> 24-in-32 sample format, where the "reference dB level" is (2^8)+1, not
> zero. This type of format is going to get very common, and is already
> used by the RME cards, the ICE1712 (Envy24) and others. I made some
> huge errors for a long time trying to use a straightforward approach
> toward converting this kind of sample value to a -1,+1 version. Its
> much easier converting it to dB, but thats not much use for us.
>
> Do you have some magic that can magically convert a sample value in the
> range(s):
>
> -(2^24) ... -((2^8)+1) ... GAP ... (2^8)+1 ... (2^24) - 1
>
> to a scaled value without incredible processing penalties ?
>
> --p
>
Huh? You argue for computation in the card's native format and then you
present a format that can't even be used mathematically without SOME kind of
conversion ??
--- james mccartney james_AT_audiosynth.com <http://www.audiosynth.com>
SuperCollider - a real time synthesis programming language for the PowerMac.
<ftp://www.audiosynth.com/pub/updates/SC2.2.7.sea.hqx>
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