Upsampling and oversampling are essentially the same thing. Try a search under upsampling. Craig |
Upsampling is converting 16 bit data to 20-24 bit data so a different kind of filtering can be used when the data is converted from a digital signal into an analog signal. The word on the street is that typical digital sounds so "unrefined" do to the radical nature of the brickwall filter used to block all frequencies exceeding 20K or so. 24 bit, high frequency sampling uses "kinder, gentler" filtering which imparts greater "finesse" to the music. After all, isn't "finesse" the ultimate goal of audio? I'm looking forward to the day when I'm sitting in my easy chair and thinking: "I just can't imagine this any better". |
Question: Does an old 16bit CD really have all the information on it (beyond 16bit) so you can change it to 24bit?? This has always confused me about unsampling? |
Dweller is confusing "upsampling" with "resolution enhancement". Upsampling means that we resample the input stream (i.e. 44.1 khz CD) at a higher sampling rate, retaining the original 16 bit word length.
If the higher sample rate is a non-integral multiple of 44.1 (i.e. 96 or 192 khz) one must calculate totally new sample values for each point in the new data stream. If the higher rate is an integral multiple 044.1 (i.e. 88.2, 176.4 etc.) then the original samples become a direct part of the new output stream. This is standard oversampling. Again we retain the original 16 bit word length.
Resolution enchancement is an attempt to extrapolate extra data beyond the original 16 bits in the CD data stream. There are 3 ways which may be used together. First, the digital reconstruction filter will generate extra bits as part of its calculation process. These may be used to extend the signal. Second the designer may add some form of dither (a small amount of digital noise) to create extra bits beyond 16. BTW, note that any didgital audio systems requires a certain amountof dither to achieve good linearity at small signal levels. Third, the designer may use a software algorithm to guess at the extra bits by analyzing the original 16 bit data stream.
Many manufacturers really mean upsampling + resolution enhancement when they advertise upsampling. They are independent processes, however. |
In short, a CD encoded in 16/44 has no information beyond those bits. Interpolation is not finding something that's there; it's guessing at the existence of something and adding it.
24/96 encoding on the other hand is a real advance, and of course a 24/96 dac is necessary to fully decode these recordings. However, other factors in a dac design may not allow all those bits to come through as musical information: if the dac is not well designed, noise, for example from the power supply, or jitter, will nullify the advance represented by 24/96.
That is partially why a well-designed 20-bit CD player w/a quiet and dynamic dac and output stage will probably beat a cheap nasty DVD player with a 24/96 dac. |
I think that most people would agree that the designer's implementaion of the technology is more important than the technology. Many people rave about some 24/96 or 24/192 designs, but some rave about the non-upsampling designs of Audio Note or Sakura.
It's probably best to listen to as many as possible in your price range. Most will sound different from each other...even the units that upsample to 24/96. It really comes down to the design and your personal preference. |
Thanks for keeping the informative posts coming.
I found some interesting links abount Perpetual Technology digital gear:
http://www.jeffchan.com/audio/p-1a-vs-d2d-1.html
http://www.jeffchan.com/audio/daif.html
This is the first negative stuff I have read about Perpetual that seems credible. |
This reminds me a lot of videotape or film. In video there are 30 frames per second. If you try to improve this image (using the original 30 fps) it can only be assumed that you MUST be adding (THAT which was not already THERE to begin with).
One could duplicate each frame an additional 1, 2, 3 or however many times, and play them back at a faster rate. This might impart a "richer" more real looking image, but it's still only made up of what was there to begin with.
One might compare two consecutive images and interpolate what an image between these might look like and insert this creation. THIS still doesn’t give you higher resolution.
To my way of thinking up sampling isn't real sound improvement, its sound smoothing. The very nature of interpolative up sampling seems to fly in the face of what many folks on this site claim to desire: The BEST… The most accurate reproduction of the original sound - TAS.
I suspect that THIS version of “up sampling” being interpreted as “hi fidelity” is why so many folks continue to tout their vinyl.
It only stands to reason that the only way to gain higher resolution is to sample more frequently (capture more information) and play this information back at the appropriate corresponding rate(s).
So... 24/96... 24/192... HELL YES! |
I just got a HDTV set which does line-doubler and the picture is terrific. I have not heard the CD with upsampling yet, however, I think it should be a positive one. |
Tok20000, there is plenty of negative discussion on the Perpetual gear on http://AudioAsylum.com. Seems that Perpetual is having software problems with some customers returning their gear several times for updates with varying degrees of success. |
I found it interesting the experiment the guy did at the webpages that I listed aove. It seemed like conclusive proof (if he was telling the truth) that Perpetual Tech gear was not reproducing music accurately.
Anyway... just my 2 cents.
Keep up the good comments. |
The comment about "not reproducing music accurately" in the aforementioned web site was directed towards the resolution enhancement feature of the P-1A.
Upsampling is a related, but different process. Together with jitter reduction, upsampling offered me a clearer, less grainy, much crisper reproduction of the music. I think it's worth an audition if you can stomach the cost. PT does offer a 30-day trial.
In my opinion, however, SOCS is the real strong point of the P-1A. That's where you really appreciate the price/performance advantage of the P-1A.
I own a P-1A and leave resolution enhancement off, but some people may prefer to have it on. It really depends on your gear and your taste. My experience has been that resolution enhancement *can* make *some* music sound "better". |
