linuxaudio.org

On Mon, 2009-02-16 at 10:50 -0700, Bearcat M. Şandor wrote:

quoted text
> ok, so i'm confused.  If you're saying that upsampling is generally a bad 

Say you have a CD with nothing but 74 minutes of "perfect" 440Hz sine

wave. As CDs are, the data is at 44.1k, which means that it can contain

only frequencies below 44.1k/2 (< 22050Hz). If you upsample this sine

wave to 96k, you will have 96k PCM data that contains a "perfect" sine

wave at 440Hz. You've added nothing to the signal so nothing has

happened.
.. except for the fact that the sample rate conversion will cause

distortion, noise and phase issues. There are really good algorithms

(libsamplerate) or obscenely good ones (check out izotope's scores on

http://src.infinitewave.ca/ ). But nevertheless none of them are perfect

and none of them cad add more "sound" to the original.
You can expand this naive example to any sound contained on a CD. The CD

will always contain only frequencies below 22050Hz, any upsampled

version will only have frequencies below 22050Hz however high of a

sample rate you choose. Except for the distortion caused by the

algorithm which will contain frequencies above 22050Hz.
> thing why does one pay extra for it in  a product like this:

quoted text
> http://www.meridian.co.uk/product-model/g-series/g082-upsampling-compact...

> player.aspx ?

Good marketing?
I find it hard to believe that upsampling PCM data does anything that a

proper DAC doesn't. Many DACs use techniques to give the same benefits

what the meridian web page describes as the benefit of upsampling:

"filtering to take place far beyond the range of human hearing". People

who know more about DACs can pitch in and provide more precise

information if needed.
Let's ask the question the other way around: if upsampling is a superior

way to convert from digital to analog, why do we see upsampling being

mentioned only in obscenely expensive hi-fi CD players? Why Lynx,

Apogee, RME, etc. don't use this technology in their highly praised

converters?
 Sampo
_______________________________________________

Linux-audio-user mailing list

Linux-audio-user@lists.linuxaudio.org

http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user