Newsgroup: it.comp.macintosh
Titolo: Encorder Dolby Surround?

Salve a tutti i musicofili e non. La domanda e':
Esiste un encoder Dolby Surround per Mac, non so qualcosa tipo Plug-in VST o altri "cosi"?
Come si chiama e se sapete il sito in modo da darci un occhio...
Ciao e grazie
Franco

 
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ci studio su.
Beh, fammi sapere e grazie in anticipo...
Ciao
Franco

 
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 chiama e se sapete il sito in modo da darci un occhio...
Scusami se sono fortemente OT, ma tu usi FastWeb? Se si' come ti va
(velocita', connessione, ecc.)? Ehm, usi un mac, vero? :-))
Ciao e grazie,
Marco
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 cercare informazioni in merito.
Il decoder Dolby Surround (diverso dal Dolby Digital) manda al canale
centrale la somma dei canali destro e sinistro, mentre manda al canale
posteriore la differenza tra il canale destro e quello sinistro (D-S)
con un certo ritardo.
Nic :-)
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Remove "levami" to reply

 
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 Ma "il canale posteriore" sono DUE...
Barbatrucco.... :)
Nel Dolby Surround (o Pro Logic) e' mono, anche se l'uscita e' per due altoparlanti.
Quello anteriore viene ricavato per filtraggio dei canali dx e sx se non
erro, mentre nel dolby digital ogni canale ha una traccia audio indirizzata singolarmente.
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 basi teoriche non ne ho, per ora.
Infatti penzavo che il DSP si basasse su particolari frequenze che erano
state enfatizzate in sede di post-produzione (se ci fai caso i rumori
che vengono dalle casse posteriori sono o i rumori di fondo di
chiacchiericcio o i jet o automobili e camion, mentre nel canale
centrale finisce la voce umana, che usa una gamma piuttosto ristretta di
frequenze).
Qualcuno in grado di illuminare?
Saluti     Giovanni
per rispondere sostituire 
tin.it
 con 
mac.com
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 Ma, ripeto, le mie sono osservazioni pratiche; basi teoriche non ne ho, per ora.
Vai bene cosi' ;-)
Ciao
Franco.

 basi teoriche non ne ho, per ora.
http://www.dolby.com/tech/l.ml.9811.surmix.s.pdf
 pag 103 e succ.
8.1 Encoder
The Encoder adds the center channel input C, attenuated by 3 dB, to the
left and right input signals, L and R. The results are sent through
all-pass networks providing frequency-dependent phase-shift and fed to
the left and right total outputs, Lt and Rt.
The surround input S is attenuated by 3 dB, bandpass filtered from 100
Hz to 7 kHz, and passed through a Dolby B-type encoder modified to
produce 5 dB of noise reduction rather than the normal 10 dB. The result
is sent through a separate all-pass network and added to the Rt output
and subtracted from the Lt output. The S input therefore, yields two
surround signals of opposite polarity from the Lt/Rt encoder outputs.
All processing in the surround path contributes to the total degree of
phase shift for that channel. The all-pass networks are designed so that
over the range of the surround bandpass filter, the phase shift of the
surround path output always lags that of the left and right by as close
to 90 degrees as pratically possible. All-pass networks with this
property have large frequency-dependent phase lag. Thus for instance at
1 kHz, the left and right paths through the Dolby Model SEU4 give phase
shifts of roughly -550 degrees, while the surround path, measured at the
right total output, has about 90 degrees more lag (approximately -640
degrees total).
8.2 Decoder
The Dolby Surround decoder detects the equal amplitude in phase (center)
and equal amplitude inverted (surround) signals. These signals, combined
with the Left and Right signals during encoding, are decoded by the
steering matrix based on which signal is dominant at any time. The
Center channel information can either be fed from the Center channel
input of the encoder or sent to both the Left and Right inputs equally.
The decoder does not differentiate between the two methods. For this
reason, signals panned to the center of the left/right bus will appear
in the Center channel output after decoding, not the Left and Right
channels.In the SDU4 decoder the input signals are first fed to the
input level control section to match the decoder reference level to the
encoder reference level. The noise sequencer, which generates the
calibration noise used during the speaker system setup, is added to the
output of the input level controls and is fed to the input of the matrix
steering decoder. The matrix steering decoder routes the Center channel
signal and controls the level of each of the four matrix outputs to
increase the separation between channels whenever possible. The Left,
Center, and Right signals are then sent to the master volume control.
The Surround channel is first sent to an anti-aliasing filter, an
adjustable length digital delay, a 7 kHz low pass filter, and a Dolby
B-type noise reduction decoder, which has complimentary modifications to
match the B-type noise reduction encoder used during the surround
encoding process. The output of this signal chain is then sent to the
master volume control. The output of the master volume control is the
output of the decoder.


 
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listen to aaria (two and a Mac): 
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album lo faccio Prologic-compatibile :-)
Si, ma poi mi dici come hai fatto ;-)
Ciao
Franco

 
(Remove the hyphen! Spambusters at work!)
listen to aaria (two and a Mac): 
http://www.mp3.com/aaria
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Comunque: bella storia 'sto thread, ma siamo OT da far paura :-)
Bella si. Almeno siamo sulla stessa orbita.
Non siamo OT col subject, ma se preferisci andiamo "private".
Ciao
Franco

 
(Remove the hyphen! Spambusters at work!)
listen to aaria (two and a Mac): 
http://www.mp3.com/aaria
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