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    :suya: (newt@stereophonic.space)'s status on Monday, 16-Sep-2024 22:56:16 JST:suya::suya:
    in reply to
    • Haelwenn /элвэн/ :triskell:
    • Volpeon :drgn_verified: :drgn_smol:
    @lanodan @volpeon you're wrong. Fuck it, I'll throw you a bone.

    First, the reason why CD Audio used 44.1kHz instead of plain 40kHz is because low-pass filters fucking eat shit. You just can't cut out >20kHz frequencies in analogue, so there's some space to work with.

    Second, aliasing is actually a thing. E.g. when you sample sound at 44.1kHz rate (or 48kHz if you're classy), higher frequencies might alias into the audible range and you will get shit instead of the sound you wanted to record. More on Wikipedia (https://en.wikipedia.org/wiki/Aliasing).

    Third, oversampling leads to higher sound quality because it allows dithering to remove sampling noise (aka quantisation error). There are several tricks that allow pushing most of that noise into the upper inaudible frequencies, leaving stuff below 20kHz more or less noise-free. Also, more on Wikipedia (https://en.wikipedia.org/wiki/Dither).

    Fourth, going back to DACs, higher resolution DACs work basically with the same principle but in reverse, allowing to reproduce signals closer to the original. Btw they aren't even 384kHz PCM. Most ADCs and DACs today are DSM (like in DSD format) and operate at 2.8224MHz or a multiple of that with 1-bit sample size. Again, more on damn stupid Wikipedia (https://en.wikipedia.org/wiki/Delta-sigma_modulation).

    TL;DR you probably should think about hi-res audio not as a means to listen to bat sonar or dolphin orgasm screams or whatever but as a form of anti-aliasing. Sorta similar to MSAA for graphics.

    There, you made me do this. I hope you're happy now.
    In conversationabout 2 months ago from stereophonic.spacepermalink

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    1. Domain not in remote thumbnail source whitelist: upload.wikimedia.org
      Aliasing
      In signal processing and related disciplines, aliasing is the overlapping of frequency components resulting from a sample rate below the Nyquist rate. This overlap results in distortion or artifacts when the signal is reconstructed from samples which causes the reconstructed signal to differ from the original continuous signal. Aliasing that occurs in signals sampled in time, for instance in digital audio or the stroboscopic effect, is referred to as temporal aliasing. Aliasing in spatially sampled signals (e.g., moiré patterns in digital images) is referred to as spatial aliasing. Aliasing is generally avoided by applying low-pass filters or anti-aliasing filters (AAF) to the input signal before sampling and when converting a signal from a higher to a lower sampling rate. Suitable reconstruction filtering should then be used when restoring the sampled signal to the continuous domain or converting a signal from a lower to a higher sampling rate. For spatial anti-aliasing, the types of anti-aliasing include fast approximate anti-aliasing (FXAA), multisample anti-aliasing, and supersampling. Description...
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      Dither
      Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often one of the last stages of mastering audio to a CD. A common use of dither is converting a grayscale image to black and white, so that the density of black dots in the new image approximates the average gray level in the original. Etymology The term dither was published in books on analog computation and hydraulically controlled guns shortly after World War II. Though he did not use the term dither, the concept of dithering to reduce quantization patterns was first applied by Lawrence G. Roberts in his 1961 MIT master's thesis and 1962 article. By 1964 dither was being used in the modern sense described in this article. The technique was in use at least as early as 1915, though not under the name dither. In digital processing and waveform analysis Dither is utilized in many different...
    3. Domain not in remote thumbnail source whitelist: upload.wikimedia.org
      Delta-sigma modulation
      Delta-sigma (ΔΣ; or sigma-delta, ΣΔ) modulation is an oversampling method for encoding signals into low bit depth digital signals at a very high sample-frequency as part of the process of delta-sigma analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). Delta-sigma modulation achieves high quality by utilizing a negative feedback loop during quantization to the lower bit depth that continuously corrects quantization errors and moves quantization noise to higher frequencies well above the original signal's bandwidth. Subsequent low-pass filtering for demodulation easily removes this high frequency noise and time averages to achieve high accuracy in amplitude which can be ultimately encoded as pulse-code modulation (PCM). Both ADCs and DACs can employ delta-sigma modulation. A delta-sigma ADC (e.g. Figure 1 top) encodes an analog signal using high-frequency delta-sigma modulation and then applies a digital filter to demodulate it to a high-bit digital output at a lower sampling-frequency. A delta-sigma DAC (e.g. Figure 1 bottom) encodes a high-resolution digital input signal into a lower-resolution...
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