GStreamer: Past, present, and future
Posted Oct 30, 2010 0:09 UTC (Sat) by gmaxwell
In reply to: GStreamer: Past, present, and future
Parent article: GStreamer: Past, present, and future
There is lots of misinformation on this subject out there.
Given unlimited precision samples a signal which has no energy above the the system nyquist is _perfectly_ re-constructable, not just "good".
If the signal does have energy above the nyquist then it's not "no hope": the system is under-determined and there are a number of possible reconstructions.
Of course, we don't sample with infinite precision but increasing the sampling rate is a fairly poor way of increasing the SNR for lower frequencies if thats your coal. For example, a 1 bit precision 3MHz process can give as much SNR in the 0-20kHz range as a 20 bit 48khz process but it takes about 3x the bitrate to do so.
24bit converters with >110dB SNR are readily and cheaply available. These systems can represent audio as loud as 'dangerously loud' with the total noise still dwarfed by the thermal noise in your ear and the room around you. It's effectively infinite precision. Heck, given reasonable assumptions (that you don't need enough dynamic range to cover hearing damage to the faintest discernible sounds) well mastered CDDA is nearly so too.
There has been extensive study of frequency extension into the ultrasonic, and none of the studies I've seen which weren't obviously flawed could support that hypothesis. If this perception exists it is so weak as to be unmeasurable even in ideal settings (much less your common listening environment which is awash in reflections, distortions, and background noise). There also is no real physiological basis to argue for the existence of significant ultrasonic perception Heck, if you're posting here you're probably old enough that hearing is mostly insignificant even at 18kHz (HF extension falls off dramatically the early twenties for pretty much everyone) much less higher.
But hey if you want to _believe_ I've got some dandy homeopathics to sell you.
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