[MPlayer-dev-eng] Re: Moving the audio plugins to libmpcodecs - design of plugin management

[Tobias Diedrich]

Anders Johansson wrote:

> Three reasons I wan to get rid of fixed point:
> 1. Poor SNR (signal to noise ratio) cause quantization noise is
> accumulated in the plugins.
> 2. Almost impossible to write filters that don't have problems with
> fixed point overflow (to get around they have to use scaling which ads
> noise)
> 3. Quantization in filter-taps makes it very hard to design feedback
> structures that are stable (thats why it took me s long to finish the
> EQ) and again it ads necessary scaling and thus noise. An example is
> the EQ i have written reduces the SNR from 96dB (which is what you get
> from int16) to 69dB (which is clearly audible) and there is nothing I
> can do about it.

How about 32bit integer instead of 16bit integer ?

That should be high enough precision to get a good SNR with fixed point
algorithms and should still be faster than floating point IMHO.

If I were to design this audio plugin structure I would use 32bit signed
integer internally, convert to this in the beginning and convert to
device precision (Noise shaping would be desired if the PC is fast
enough) at the end of the plugin chain.

-- 
Tobias								PGP: 0x9AC7E0BC
Shortly into her spell, the No-Camping Enforcer appeared behind her, again
unnoticed by Sakura.