linuxaudio.org

On Sun, Dec 23, 2012 at 05:05:47PM -0500, Thomas Vecchione wrote:
> On Sun, Dec 23, 2012 at 4:35 PM, Fons Adriaensen wrote:

quoted text
>

> > You seem to think that resampling is some very complex operation

> > that involves compromises and deliberate loss of quality, just as

> > e.g. mp3 or ogg encoding. That is not the case. As I wrote, it's

> > just a filter. It's a bit more difficult to write than e.g simple

> > EQ because the coefficients are changing for each sample. But in

> > the end the DSP operation that is done is exactly the same as for

> > a simple FIR filter, and any loss of quality will be similar as

> > well.

> >

>

> If this is the case, why would we have several different resampling

> algorithms with varying levels of quality?

The usual tradeoff between quality and CPU use. Today it shouldn't

matter at all for stereo. But if you have 64 channels to resample in

real time it still does.
'Quality' is a bit of a misnomer in the case of e.g. zita-resampler

and the 'sinc' options of libsamplerate. The only difference is in

the frequency response for frequencies near half the sample rate.
> > Which in practice means it's *irrelevant*. Your 24 bit DACs may

quoted text
> > provide 145 dB S/N in theory, in practice even the most expensive

> > ones don't even have 120 dB. The limit is the analog electronics,

> > and it is not imposed by technology but by physics. Even with the

> > best 24-bit converters you can buy at least the lower 4 bits will

> > be pure noise. And for a 32-bit converter (snake oil if there ever

> > was any), the lower 12 bits will be noise. That's assuming you have

> > a high level line input. For mic signals the actual S/N ratio will

> > even be lower, much lower in most cases.

> >

>

> All very true, and I certainly don't dispute this, but also I am not sure

> as to why exactly it is relevant to this conversation either.

You mentioned that resampling would add noise. It does, but as shown

above the noise you have anyway is already at a much higher level, so

anything added by resampling will not make any difference.
Ciao,
--

FA
A world of exhaustive, reliable metadata would be an utopia.

It's also a pipe-dream, founded on self-delusion, nerd hubris

and hysterically inflated market opportunities. (Cory Doctorow)
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