Timeline for What is the purpose of gamma correction in today's screens and how does it relate to graphics and photography?
Current License: CC BY-SA 4.0
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| Jun 9, 2019 at 17:58 | history | edited | Myndex | CC BY-SA 4.0 |
minor fix
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| Jun 1, 2019 at 19:05 | history | edited | Myndex | CC BY-SA 4.0 |
Clarified a bit about CRT non linearity
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| May 2, 2019 at 3:16 | comment | added | Myndex | Remember we are talking sine waves here — a sound can be split into a set of individual sine waves. A square wave for instance is all odd harmonics from the fundamental frequency up to infinity. When working with sine waves, the "level" is a function of RMS not peak. Also, yes a "linear digital encoding" but of a logarithmic value - sound is 20log. Similar to how a DPX image is a linear encoding of film density, but film density is log, thus a DPX is referred to as log. But as for pre-emph in digital, it is indeed used (or was) see wiki.hydrogenaud.io/index.php?title=Pre-emphasis | |
| May 2, 2019 at 2:26 | comment | added | Zeus | In linear digital encoding, half of the voltage is half of the digital range (by definition), i.e. loss of 1 bit of resolution. This is a lot for something that is perceived as 'a bit softer' (-6dB, that's the figure I meant, not 3). If we want to capture the required ~35dB at least (for speech or orchestra), that's already a 6 bit loss for the softest sounds (and even then, if properly normalised). I'm aware of the 'analog' emphasis (which was a bit different and frequency-dependent), but never heard of one used for digital, hence my questions... | |
| May 1, 2019 at 10:00 | comment | added | Myndex | I think there's a stack exchange related site that would welcome audio questions. Regardless: Each bit in 16 bit audio equals 6 dB (voltage), so there's a total dynamic range of 96 dB. 6dB (voltage) is "twice" (or half) as loud in voltage, BUT humans tend to perceive 10 dB as a literal "half as loud" amount. Pre/De emph has been used in audio since the beginning. Records had the RIAA curve, magnetic tape used the NAB curve, etc. etc. What do you mean losing half the resolution every 3 dB ??? | |
| May 1, 2019 at 5:55 | comment | added | Zeus | Thanks @Myndex, unfortunately this would be off-topic here as a question. I'm just curious why such pre-/de-emphasis wasn't used for audio from the beginning, given that it's just as natural for hearing as for sight. By the way, I meant 16 bit per channel, of course (like on CD); linear 8-bit audio (which formally exists) is arguably more horrible than the linear 8-bit video from your example (which doesn't even exist as a standard). I understand the tradeoffs are lower, but the benefits are high: losing half of the resolution every 3 dB feels insane... | |
| May 1, 2019 at 5:00 | comment | added | Myndex | Hi @Zeus, there are several reasons (if you ask this as a question I can give a more in depth answer). Basically, even at 16 or 24 bit, audio streams are a far lower bandwidth than video (in general), and computationally easer to handle. Nevertheless, audio DOES use these types of pre-emphasis and de-emphasis in many cases (particularly low bit rate). And in fact hearing is also non-linear (as is all perception) but 8 bit audio is "sort of" like 4 bit per channel video. Remember that 8 bit per chan video uses a total of 24 bits per pixel, so the comparison to 16 bit audio is apples/oranges. | |
| May 1, 2019 at 4:43 | comment | added | Zeus | I always wondered why doesn't the audio industry use the same approach but instead throws 16+ bits per sample at it... | |
| Apr 30, 2019 at 19:50 | review | Late answers | |||
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| Apr 30, 2019 at 19:40 | review | First posts | |||
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| Apr 30, 2019 at 19:37 | history | edited | Myndex | CC BY-SA 4.0 |
added 88 characters in body
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| Apr 30, 2019 at 19:31 | history | answered | Myndex | CC BY-SA 4.0 |