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'[PICLIST] [PIC] How much "PIC-power" to do SP/DIF '
2001\02\21@191111 by Kyrre Aalerud

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I have been fondling with the idea of using a pic to parse two stereo SP/DIF (Actually TTL, but same format :-) signals from a Soundblaster Live card, or 5.1 card.

Creative was simply to cheap to include such horsepower, instead they made the Live 1024 card with two stereo digital outputs for Front left/ringht and Back left/right. (And the plug also delivers some power to a output module) In the 5.1 They did away with the output module power, and added the third digital channel for the center and subwoofer... Or, so it seems because the card has two more channels, and the old output module won't work anymore.
I read somewhere that four channel SP/DIF in normal PCM mode is possible, so the question would be: Who will make something :-)  I just had to take a closer look at this !

How much power would I possibly need ???

I already know that for each sample, two 32-bit words are transmitted, which results in a bit-rate of:
   2.8224 Mbit/s  (44.1 kHz samplingrate, CD, DAT)
   3.072  Mbit/s  (48 kHz sampling rate, DAT)
   2.048  Mbit/s  (32 kHz sampling rate, for satellite purposes)

All of theese would be nice to handle, but the Soundblaster only uses 48 kHz...
BUT, if the data is NOT PCM, we shouldn't change it, cause then it might be AC3 or something.  This should be passed straight trough...

The question is if it can be done, and most of all: with some pic ???

   KreAture

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2001\02\22@041753 by Chris Carr

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I would take a look at the Crystal Semiconductor Products

http://www.cirrus.com/

In the first instance and just use a PIC to control them

Goto http://www.cirrus.com/design/products/index.cfm?DivisionID=3

and look at the applications down the right hand side
for some ideas

Regards
Chris


I have been fondling with the idea of using a pic to parse two stereo SP/DIF
(Actually TTL, but same format :-) signals from a Soundblaster Live card, or
5.1 card.

Creative was simply to cheap to include such horsepower, instead they made
the Live 1024 card with two stereo digital outputs for Front left/ringht and
Back left/right. (And the plug also delivers some power to a output module)
In the 5.1 They did away with the output module power, and added the third
digital channel for the center and subwoofer... Or, so it seems because the
card has two more channels, and the old output module won't work anymore.
I read somewhere that four channel SP/DIF in normal PCM mode is possible, so
the question would be: Who will make something :-)  I just had to take a
closer look at this !

How much power would I possibly need ???

I already know that for each sample, two 32-bit words are transmitted, which
results in a bit-rate of:

   2.8224 Mbit/s  (44.1 kHz samplingrate, CD, DAT)
   3.072  Mbit/s  (48 kHz sampling rate, DAT)
   2.048  Mbit/s  (32 kHz sampling rate, for satellite purposes)

All of theese would be nice to handle, but the Soundblaster only uses 48
kHz...
BUT, if the data is NOT PCM, we shouldn't change it, cause then it might be
AC3 or something.  This should be passed straight trough...

The question is if it can be done, and most of all: with some pic ???

   KreAture

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2001\02\22@180401 by Kyrre Aalerud

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Thanx, Great info, but this is not exactly what I am after...
I have 2 or 3 digital stereo sources that are already SP/DIF.  I want two of theese or hopefully all six into a single digital signal to send to digital home cinema decoders...

any more info ?

{Original Message removed}

2001\02\22@201918 by Bob Ammerman

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What is being asked here is the ability to encode 6 channels of digital
audio, transmitted as three SP/DIF signals into a single 5.1 encoded audio
signal, again transmitted as a single SP/DIF signal.

I would guess that this encode process is well outside the possibilities of
even the fastest  PIC or largest SX without substantial external support.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\23@062227 by Kyrre Aalerud
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But, for the four channel system al that is done is taking 2 sp-dif signals and interleaving the "cells" it the data, changing the preamble of the first cell in the rear sp-dif signal.  Altso changing the bit 0 of the control-bits to 1 for four channel transmission.
The output signal will have twice the bitrate of one of the incoming signals.  one can use a 422 tranciever to recieve and send the SP/DIF.  Then you don't have to deal with the double data rate clocked biphase signal in the PIC.
The data is transferred ad 32 bit words, so 64 bits can be used if we use no extra buffer.  We would however need another 64 bits since we will recieve two 32 bit words in paralell while transmitting the previous two...

Would be rally fun to code this :-)  I think I would let C rest abit and do this in ASM :-)))

   KreAture

{Original Message removed}

2001\02\23@083109 by Bob Ammerman

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----- Original Message -----
From: Kyrre Aalerud <spam_OUTkreatureTakeThisOuTspamC2I.NET>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Friday, February 23, 2001 6:22 AM
Subject: Re: [PIC] How much "PIC-power" to do SP/DIF multichannel ?


But, for the four channel system al that is done is taking 2 sp-dif signals
and interleaving the "cells" it the data, changing the preamble of the first
cell in the rear sp-dif signal.  Altso changing the bit 0 of the
control-bits to 1 for four channel transmission.
The output signal will have twice the bitrate of one of the incoming
signals.  one can use a 422 tranciever to recieve and send the SP/DIF.  Then
you don't have to deal with the double data rate clocked biphase signal in
the PIC.
The data is transferred ad 32 bit words, so 64 bits can be used if we use no
extra buffer.  We would however need another 64 bits since we will recieve
two 32 bit words in paralell while transmitting the previous two...

Would be rally fun to code this :-)  I think I would let C rest abit and do
this in ASM :-)))

   KreAture

KreATture:

As I read the SP/DIF specs I didn't see anything about bit rates other than
apporpriate for 44.1 x 2 channels, 48 x 2 channels and 32 x 2 channels.

If you are right, this is still too fast for PICs, I would think, but might
be doable with a PIC and a little bit of external support (some sort of PLD
or such).

One issue is clock rates. It would be a _big_ help if all the incoming
SP/DIF signals shared a common clock, which they probably do off the SB
board. Otherwise you'd have a hugh headache due to clock slip between the
signals.

What kind of equipment would be able to handle a signal of double bit rate
with 4 channels in it?

Doesn't most gear expect AC3 or some such thing, which is a mutichannel
_encoded_ signal?

Where is the documentation for these encoding schemes?

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\25@162627 by Kyrre Aalerud

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> As I read the SP/DIF specs I didn't see anything about bit rates other than
> apporpriate for 44.1 x 2 channels, 48 x 2 channels and 32 x 2 channels.
>
> If you are right, this is still too fast for PICs, I would think, but might
> be doable with a PIC and a little bit of external support (some sort of PLD
> or such).
>
> One issue is clock rates. It would be a _big_ help if all the incoming
> SP/DIF signals shared a common clock, which they probably do off the SB
> board. Otherwise you'd have a hugh headache due to clock slip between the
> signals.
>
> What kind of equipment would be able to handle a signal of double bit rate
> with 4 channels in it?

The Sony DB830 can do it, and that is what I use.  That's why this is so interesting :-)

> Doesn't most gear expect AC3 or some such thing, which is a mutichannel
> _encoded_ signal?

For more than two channels, as I see it, there are only two options.  Four channel PCM or some encoded multichannel.

> Where is the documentation for these encoding schemes?

I am digging as we type :-)

If it is possible,, it will be documented... somewhere. :-)

   KreAture

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