Electronics project notes/Audio notes - multichannel and surround: Difference between revisions
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'''Fantasound''' (cinema) | '''Fantasound''' (cinema) | ||
Disney's Fantasia (1940!) had a three-channel soundtrack (four on the film; left, center, right, and the fourth controlling volume). | Disney's Fantasia (1940!) had a three-channel soundtrack (four tracks on the film; left, center, right, and the fourth controlling volume). | ||
There were other soundtracks from the time recorded in this way | There were other soundtracks from the time recorded in this way. | ||
This was basically the first experiment, and it didn't take off in a big way (the film was not really a success), | This was basically the first experiment, and it didn't take off in a big way (the film was not really a success), | ||
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'''Cinerama''' (cinema) | '''Cinerama''' (cinema) | ||
Cinerama is perhaps better known for having widescreen via multiple projections on a large curved screen (cf. Cinemascope, IMAX), | Cinerama is a wider concept, perhaps better known for having widescreen via multiple projections on a large curved screen (cf. Cinemascope, IMAX), | ||
but it also had seven channels of sound (five behind the screen, two rears) | but it also had seven channels of sound (five behind the screen, two rears) | ||
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'''Quadraphonic''' {{comment|(frequently also pronounced quadrophonic?)}} | '''Quadraphonic''' {{comment|(frequently also pronounced quadrophonic?)}} | ||
Quadraphonic comes from the 1950s, and | Quadraphonic comes from the 1950s, and became more widely and commercially known in the 1970s, if relatively briefly. | ||
Quadraphonic comes in roughly three types: | Quadraphonic comes in roughly three types: | ||
* four separately stored channels | * four separately stored channels | ||
:: or, if you're Suzanne Ciani, presumably four separately generated channels{{verify}} | |||
* four channels mixed into stereo in a separable way | * four channels mixed into stereo in a separable way | ||
:: which makes | :: which makes commercial sense in that you could sell one recording (particularly vinyl records, which can only sensibly go up to 2 channels) that everyone can play but some people can get more out of | ||
:: there were multiple ways to do this, some better, some worse | :: there were multiple ways to do this, some better, some worse, all somewhat creative | ||
* a way to add ambiance from regular stereo | * a way to add ambiance from regular stereo | ||
:: which is | :: which is subtler, but a nice addition that works on most any audio you feed it | ||
Revision as of 12:57, 25 September 2023
Why
Binarual and headphones are two extra cases we forget to think about
Earlier experiments
Dolby glossary
For context
- Dolby is a company
- Dolby Surround tends to refer to multi-channel matrix schemes (initially analog, later digital)
- Dolby Digital are digital codecs.
Sometimes the channel stuff and the codec stuff is strongly related (or implied by context), so we generally don't need to be picky about terms, but knowing the distinctions can be useful.
Dolby Stereo (1976) seems to group both:
- Dolby SVA - A matrix decoding scheme,
- from two channels on optical film
- to four: left, right, center, and a mono rear surround
- was used in cinemas, to give the option for encompassing sound based on existing film (avoiding separate multitrack and possible sync issues)
- playable on regular stereo as-is, and consumer SVA decoders existed
- soundtracks were sometimes SVA as a selling point, in that they were playable everywhere, but would would sound cooler on specific systems.
- Dolby Stereo 70mm - Noise reduction used on 6-channel magnetic tracks on 70mm film print.
- ...so not something any of us consumers would ever deal with
Dolby Surround (1982) is a marking used on players that used a simplified passive matrix decoder to play SVA(verify) into left, right, and surround (the center channel was fed equally from left and right, because that works out as phantom center)
(note: Dolby made things very confusing in 2014, see below)
Dolby Pro Logic (1987)
- amounts to an expansion of what Dolby Surround does (still four channels)
- implemented with ICs
- does some gaining (and some frequency filtering?(verify)) depending on what's currently dominant, without changing total energy, which gives the perception of better separation (Dolby calls this 'steering')
Dolby Pro Logic II (2000)
- takes regular stereo or Dolby Surround
- produces five sensible full frequency channels (left front, center, right front, left rear, right rear).
- Basically, the gaining/steering is better than before, meaning it adds a reasonable 'in the middle of the sound' feeling to most any stereo input
Dolby Pro Logic IIx (2003)
- Can take regfular stereo, Dolby Surround, or 5.1.
- similar, can output 6.1 or 7.1
Dolby Pro Logic IIz (2006)
- similar, goes up to 9.1 height systems
Dolby Surround is, since 2014, used in a completely different meaning than before, basically referring to part of Dolby Atmos system.
https://en.wikipedia.org/wiki/Dolby_Pro_Logic#Dolby_Surround_(2014)
Dolby Digital, a.k.a. AC-3 is just about storing audio, not about processing it. [1]
Dolby Digital Plus (a.k.a. DD+, DDP. E-AC-3 (Enhanced AC-3), EC-3) is AC-3's successor, though it seems less known outside ATSC?(verify)
[2]
DTS
DTS is a brand.
When used to refer to digital audio, it typically refers to the DCA (DTS Coherent Acoustics) codec, as e.g. carried over SPDI/F.
DCA is a a compressed, digital surround format.
DTS Neo:6 is a similar idea to pro logic II: produces more channels from fewer.
DTS Neo:X is similar and goes up to 11.1 height systems