On Mon, 2009-02-16 at 10:50 -0700, Bearcat M. Şandor wrote:> 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 sinewave. As CDs are, the data is at 44.1k, which means that it can containonly frequencies below 44.1k/2 (< 22050Hz). If you upsample this sinewave to 96k, you will have 96k PCM data that contains a "perfect" sinewave at 440Hz. You've added nothing to the signal so nothing hashappened. .. except for the fact that the sample rate conversion will causedistortion, noise and phase issues. There are really good algorithms(libsamplerate) or obscenely good ones (check out izotope's scores onhttp://src.infinitewave.ca/ ). But nevertheless none of them are perfectand none of them cad add more "sound" to the original. You can expand this naive example to any sound contained on a CD. The CDwill always contain only frequencies below 22050Hz, any upsampledversion will only have frequencies below 22050Hz however high of asample rate you choose. Except for the distortion caused by thealgorithm which will contain frequencies above 22050Hz. > thing why does one pay extra for it in a product like this: > http://www.meridian.co.uk/product-model/g-series/g082-upsampling-compact-disc-> player.aspx ? Good marketing? I find it hard to believe that upsampling PCM data does anything that aproper DAC doesn't. Many DACs use techniques to give the same benefitswhat the meridian web page describes as the benefit of upsampling:"filtering to take place far beyond the range of human hearing". Peoplewho know more about DACs can pitch in and provide more preciseinformation if needed. Let's ask the question the other way around: if upsampling is a superiorway to convert from digital to analog, why do we see upsampling beingmentioned only in obscenely expensive hi-fi CD players? Why Lynx,Apogee, RME, etc. don't use this technology in their highly praisedconverters? Sampo _______________________________________________Linux-audio-user mailing listLinux-audio-user@xxxxxxxxxxxxxxxxxxxxxxxx://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
