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Old 7th September 2008, 08:24 PM   #11
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Join Date: Nov 2005
Location: colorado
I wonder what a min buy would be to include licenses for
the decoder algorithms. Would the licensers be willing to release
for some type of diy community group buy and how many diyer's
would be interested?
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Old 8th September 2008, 12:15 AM   #12
NeoY2k is offline NeoY2k  France
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Join Date: Dec 2007
What about using a computer with appropriate sound card?
Use VST plugins in a "realtime virtual rackmount".
It WILL do the trick. Even if it's not "full realtime": when you need multichannel at an event you don't use Dolby anyway... (good old Behringer ADA8000... stack them up, add ADAT ports to a digital Yamaha mixing desk => standard setup.) You should be able to do that with Linux too, with a RT kernel. Search "ubuntu studio".

Use no hard drive but Compact Flash (IDE compatible), choose a portable computer processor with adapter and adequate fanless cooling (maybe adapting an old "alpha PAL" heatsink. DC/DC power supply. Won't make any noise, should fit a 3u rack. BTW, cheaper than developping your board.

If you need, make a firewire card with comprehensive chips and ready made drivers. Output i2s on balanced LVTTL trhu good connectors. Or output i2s, i8s, LJ, RJ.. Anything you want.

The computer will also do the job of crossover, filtering, and any additional DSP you may like.

Your project is exciting anyway. Good luck if you keep working on it. One of my teachers, Jean Pierre Lafont (who made the mixing desks for BBC, 20th century fox, Disney etc...) left the game when it came to digital desks: you have to be a full team of engineers, otherwise the chip no longer exists when you have finished making the software. But that's for a full mixing desk, a channel splitter should be doable.

Nicolas

Note: The product you're looking for may exist. Yamaha makes a series of DSP machines for speaker processing in large venues. If it has Dolby decoding option...
3000$
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Old 8th September 2008, 02:33 AM   #13
JinMTVT is offline JinMTVT  Canada
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Join Date: Jul 2004
Location: MTL
NeoY2K : please point to this yam product
price is not a problem here ...


Just for quick show ..this is my new house
HT's room ..here you can see the front wall that has embedded ( 2"foam/8"concrete/2"foam) IB sub array

( the garage is used as the rear chamber,
wich is reached through a 10'high 2'wide concrete chamber/port )

Click the image to open in full size.

so back to topic,
i will read the article.

i do not want to use a computer as the only source,
i find the ability to switch different sources
with an HT receiver very interesting

like connecting and old game or stereo source and beeing able to have it matrix it back to use all the speakers ..and do multiple source swith
( also video switching .. )


What do you suggest as far as digital signal goes?

my only fear here is the jitter that will be introduced from using so many conversion and going through so many chips ..

what would be the ideal path ?
we could start from there and then make the required compromises to attain my goal
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Old 8th September 2008, 03:20 AM   #14
JinMTVT is offline JinMTVT  Canada
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Join Date: Jul 2004
Location: MTL
thinking of it ...broswing products through internet..even went as far as looking at DOlby's solutions for theaters and such

at the end, the reason why i want digital outputs,
is to use the DCX for crossovers in the digital domain,
since it will be easily tunable, and lossless
and with the number of drivers i'll have,
and the quantity of possibilites, using analog crossovers is just way out of the question

i am also a bit frustrated about using analogue crossovers when eveyrthing CAN be digital
( way simpler though for stereo system )

So if i'd find an home theater receiver, comercially available, that has similar crossover options as the DCX units ..it would render all those efforts pointless.

But i have yet to find any unit that has anyhting more than " 30-350-80-120hz" sub X-OVER option

as i said before, having alot of components and chips in the line won't probably help with distortion ( jitter )
so a single component with potent recent DACs would replace ALOT of the units i plan on using

( is there any recent receiver with real high quality DAC sound ?? haven't heard any good reciever up to now,
but haven't checked any for 2-3 years so .. )
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Old 8th September 2008, 10:53 AM   #15
NeoY2k is offline NeoY2k  France
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Join Date: Dec 2007
Quote:
Originally posted by JinMTVT
NeoY2K : please point to this yam product
price is not a problem here ...
...
i do not want to use a computer as the only source,
i find the ability to switch different sources
with an HT receiver very interesting

like connecting and old game or stereo source and beeing able to have it matrix it back to use all the speakers ..and do multiple source swith
( also video switching .. )
...
Hi,
I was not telling you to use the computer as a source, but only as the DSP box. Running a PC with a RT Linux Kernel isn't very different from having a C running any RTOS (maybe Linux in some cases...) with a DSP. But on a computer, everything has really been done. The only thing you have to do is parameter what DSP you want it to do, and tell it to launch the program at boot.

You could enter the computer in digital or analog if you want. Just choose a soundcard. You may want to do a little bit of programming to add some controls on the rack (switching between digital and analog in/out, and changing the processes inside). Shouldn't be that hard.

Dolby receiver Digital out => Computer => SPDIF(i2s?) digital outs => DAC
or
Stereo (analog)=>Computer=>SPDIF outs => DAC

Etc...

But I don't really see the point in making multichannel from stereo.

http://www.yamaha-europe.com/yamaha_...060/index.html

I don't see anything for Dolby but you may have to ask them if they have plugins.
They also have Ethersound DSP, look at it.
EDIT: sorry, it's in french, search the ref in english
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Old 8th September 2008, 04:42 PM   #16
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Join Date: Oct 2001
Location: .
Presumably, the multichannel content you wish to decode comes on a disc of some sort. That being the case just buy a player capable of decoding all the relevant formats, an OPPO for example, and add the necessary SPDIF outputs.
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Old 8th September 2008, 06:44 PM   #17
Johnix is offline Johnix  France
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Join Date: Jul 2004
Location: Lyon (France)
Quote:
Originally posted by coloradosound
I wonder what a min buy would be to include licenses for
the decoder algorithms. Would the licensers be willing to release
for some type of diy community group buy and how many diyer's
would be interested?

Dolby and DTS licences are (too) expensive. For example, just being able to get the right to start a Dolby-based design costs you $5k. Well, that was 5 years ago when we start working on that DSP solution.
DTS : higher bitrate thus higher fees : $10k

And this doesn't include latest HD decoders such as Dolby Digital True HD etc...

Chips vendors such as Cirrus Logic won't sell you those chips, even if you buy 500 pces. The reason is that software covers 90% of the project developpement and that software means bugs means technical support. Cirrus Logic will not support you and the DIY community.

Now, you can still try to buy a OEM board. Try :
- vinci labs
- momentum data systems
- i-lab america
- yba
Click the image to open in full size.
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Old 8th September 2008, 07:41 PM   #18
Johnix is offline Johnix  France
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Join Date: Jul 2004
Location: Lyon (France)
Quote:
Originally posted by rfbrw
Presumably, the multichannel content you wish to decode comes on a disc of some sort. That being the case just buy a player capable of decoding all the relevant formats, an OPPO for example, and add the necessary SPDIF outputs.

I still think that tweaking an AVR is the best option for that specific application because the universal player can't perform :
- 7.1 channels
- 2.0 to 5.1 matrix
- volume control
- source selection
etc...
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Old 8th September 2008, 08:52 PM   #19
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Join Date: Oct 2001
Location: .
Quote:
Originally posted by Johnix



I still think that tweaking an AVR is the best option for that specific application because the universal player can't perform :
- 7.1 channels
- 2.0 to 5.1 matrix
- volume control
- source selection
etc...

Anyway, irrespective of the source, the fundamentals remain the same and are, to a large extent, device specific.
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Old 9th September 2008, 03:31 AM   #20
JinMTVT is offline JinMTVT  Canada
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Join Date: Jul 2004
Location: MTL
i'm with John...

beeing there, i'd rather have all the power options that a recent receiver provides
( myriad of inputs including hdmi 1.3, main volume,
all the surround decoding and matrix options )

so that beein said,

how do we choose the "corrrect" avr ??

and we still have to debate, what is the best path??
i am seriously worried about the excessive jitter
from all the conversions and spdif chips ...

do you believe it will be an issue ?

how long of cable can we safely run I2S lines on before getting some signal distortion ?
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