[LAU] Mono tracks to mono or stereo bus ? And sampling rate
paul at linuxaudiosystems.com
Wed Nov 25 12:34:46 UTC 2015
Again, you're missing several obvious points, all of which have been made
Nyquist says that to **perfectly** capture all frequencies up to N kHz, you
need to sample at N*2.
Human hearing ends even in the best of us at about 20kHz. We sample at
typically 40kHz plus.
The implication: this "low resolution" example you're talking about isn't
remotely close to what is happening with real world digital audio. Sure, if
you sample at 8kHz like early digital telephony (thus only capturing
frequencies up to 4kHz, the result after D->A differs substantially from
the original. But that's why we don't do that.
Also, your drawings ignore the basic point that Felix made. Your "original"
curve includes frequencies that are above the cutoff for the "sample rate"
your "digital" version uses.
On Mon, Nov 23, 2015 at 2:55 PM, jonetsu at teksavvy.com <jonetsu at teksavvy.com>
> On Mon, 23 Nov 2015 09:46:55 -0800 (PST)
> Len Ovens <len at ovenwerks.net> wrote:
> > On Mon, 23 Nov 2015, jonetsu at teksavvy.com wrote:
> > > On Mon, 23 Nov 2015 17:00:47 +0000
> > > Will Godfrey <willgodfrey at musically.me.uk> wrote:
> > >> Although it seems counter-intuitive that actually is quite wrong!
> > > Hmmmm. Not sure about intuition. A sine wave with 16 sampled points
> > > will end up like a linked list of edges. Saving that to file and
> > > resampling at 128 will only add points to the straight lines. It
> > > will not create curves as per the original. It cannot. How would
> > > it know it was a sine wave and not a guitar tone when it had to
> > > process basically what was a robotic tone ?
> > Very simplified.... Filtering. Really, watch the video a xiph.org
> > before you say any more. They compare (on analog equipment) input and
> > output wave forms at 44.1k.
> I watched the video. I still remain with what I said, really. As a
> parallel, a picture - parallel also made in this video - if you take a
> very low resolution of the Mona Lisa it will not be possible to
> reconstruct the quality of the original. The information is not
> there. This is quite obvious with pictures. Same with sampling.
> Attached is a quick drawing to illustrate. It is coarse as there are
> very few sampling points, but the principle applies. The limit is the
> finesse of the source material. If there are extremely minute changes
> in the wave then the sampling must be done at an according rate if one
> wishes to preserve the original as much as possible. Parameters of
> interpolation can be applied, but how would you interpolate a 4-bit
> Mona Lisa to show the subtleties of Da Vinci's painting ?
> Now, I would like to know that in reality things are not like that and
> that high, true-to-orignal, quality can be made from low quality sources
> so I remain open to all comments and ideas.
> Linux-audio-user mailing list
> Linux-audio-user at lists.linuxaudio.org
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