For a mini-surprise, check the prime factors of 44100.
Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
31–40 of 79 posts
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#32Earlier quoted context omitted.
Not just eventually: many effects, such as basically any non-linear mapping like a distortion, will create overtones that will immediately alias down if you are not oversampling. You either need to use some DSP tricks or oversample (usually a mix of both) to avoid this happening, which often happens in just one step of an effects chain.
Even the term "oversampling" implies that sampling beyond Nyquist rate is excessive. I think you would agree that one is not being excessive. It is necessary to sample well beyond accepted "Nyquist rate" in order to reconstruct the signal.
I'd phrase it differently.
Your signal contains all kinds of frequencies: Those you care about and those you don't want in your recording. You can't just sample at the Nyquist rate of the interesting frequency and expect all the other frequencies to vanish. They will mess with the frequencies you are actually interested in.
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#33> ...there is no point to distributing music in 24-bit/192kHz format. Its playback fidelity is slightly inferior to 16/44.1 or 16/48.... from "24/192 Music Downloads ...and why they make no sense" (2012) [1] [1] https://people.xiph.org/~xiphmont/demo/neil-young.html
High sample rate isn't useful for playback, but 24-bit is great for nuance in low intensity sound.
so for stuff which didn't properly use the dynamic range of the standard codecs?
Are human ears even capable of hearing 24 bits of dynamic range?
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#34Earlier quoted context omitted.
You’re right, but I fear this idea has become prevalent in audiophile communities where they only want to listen to files that are 96kHz or higher. In my opinion, having a high sample rate only really matters during the production phase and does not have a noticeable effect on the final form factor. If the producer uses high sample rate during the creation process, I see no reason why the listener would care if the f…
People should prefer 48k over 44.1 but not for fidelity. It would just make the world a better place if 44.1k audio files died out. The reasons it was chosen are invalid today and we're stuck with it, and now every audio stack needs to be able to convert between 44.1/88.2 and 48/96 which is a solved problem, but has a tradeoff between fidelity and performance that makes resampling algorithms a critical design feature…
https://en.wikipedia.org/wiki/PCM_adaptor
It's very likely that the 44.1 kHz rate comes from the PCM adaptors that were designed to take PCM audio and convert it to something that a video tape recorder would accept.
I watched a YouTube a few months ago about these adaptors and the presenter did the calculations showing how the 44.1 kHz 16-bit sample rate lines up with the video fields. There was a valid engineering reason for this sampling rate.
However, the stories about one of the Sony executives having a particular piece of music in mind are true, and have to do with the diameter of the disk being enlarged compared to what Philips originally had in mind. By that time the bitrate was already decided.
I still agree that 48 kHz is a better choice today, especially after reading this paper.
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#35Earlier quoted context omitted.
People should prefer 48k over 44.1 but not for fidelity. It would just make the world a better place if 44.1k audio files died out. The reasons it was chosen are invalid today and we're stuck with it, and now every audio stack needs to be able to convert between 44.1/88.2 and 48/96 which is a solved problem, but has a tradeoff between fidelity and performance that makes resampling algorithms a critical design feature…
https://en.wikipedia.org/wiki/PCM_adaptor It's very likely that the 44.1 kHz rate comes from the PCM adaptors that were designed to take PCM audio and convert it to something that a video tape recorder would accept. I watched a YouTube a few months ago about these adaptors and the presenter did the calculations showing how the 44.1 kHz 16-bit sample rate lines up with the video fields. There was a valid engineering r…
Beethoven's 9th.
> Kees Immink, Philips' chief engineer, who developed the CD, recalls that a commercial tug-of-war between the development partners, Sony and Philips, led to a settlement in a neutral 12-cm diameter format. The 1951 performance of the Ninth Symphony conducted by Furtwängler was brought forward as the perfect excuse for the change,[76][77] and was put forth in a Philips news release celebrating the 25th anniversary of the Compact Disc as the reason for the 74-minute length.
https://en.wikipedia.org/wiki/Symphony_No._9_(Beethoven)#Com...
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#36Earlier quoted context omitted.
I'm not sure what you mean here, but I would say that sampling profilers are a good example of Nyquist applied correctly for the most part: your signal (the distribution of where your software is spending its time) is likely to have an extremely low bandwidth (as in, it's basically static), so why try to sample super rapidly? It's much more of a question of whether you get enough samples to represent that distributio…
You’re talking about profiling a normal running program. If you’re profiling a benchmark that’s always executing the hot path, where exactly the hot path contribution lies becomes less clear. This is because you run into aliasing with the samples being collected at unhelpful points. Maybe if you run long enough you start to see a picture but at 1khz you’re going to have to run for a very long time. The other way alia…
One possible issue is that if sampling is even slightly biased, it can incorrectly estimate the relative frequency of different points/functions in tight inner function calls (which can't happen with infrequently called functions with a long runtime)?
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#37For a mini-surprise, check the prime factors of 44100.
It's a multiple of 7?
It doesn't have big factors?
I don't know what I'm supposed to be surprised about.
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#38Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#39> ...there is no point to distributing music in 24-bit/192kHz format. Its playback fidelity is slightly inferior to 16/44.1 or 16/48.... from "24/192 Music Downloads ...and why they make no sense" (2012) [1] [1] https://people.xiph.org/~xiphmont/demo/neil-young.html
High sample rate isn't useful for playback, but 24-bit is great for nuance in low intensity sound.
The noise floor of 16-bit music is imperceptible so for mastered music at least 24-bits is useless. Both a higher sample rate and bit depth can be useful for recording purposes - provided the room is perfectly treated and there are no external sources of noise.
Re: Sampling: What Nyquist didn't say, and what to do about it (2018) [pdf]
#40Earlier quoted context omitted.
High sample rate isn't useful for playback, but 24-bit is great for nuance in low intensity sound.
so for stuff which didn't properly use the dynamic range of the standard codecs? Are human ears even capable of hearing 24 bits of dynamic range?
Rule of thumb:
We know that 2^10 ≈ 10^3, so 2^24 ≈ 10^(3/10*24) = 10^7.2. This 7.2 is about amplitude, but what we hear is power which is quadratic in amplitude, so take a factor of 2, and you're talking 14.4 bel, or 144 decibel for 24 bit (and 2/3 of that, 96 db, for 16 bit).
(In reality it's a bit more complicated, but that's a good rough guide, see https://en.wikipedia.org/wiki/Audio_bit_depth#Quantization)