SPDIF and sound card question

GestaltH · 28th January 2008, 03:13 PM

Hi,

I am new to the whole DIY audio thing and have a few questions. I have a creative x-fi sound card with an SPDIF output. One question that I have is, does that output contain the signal for all 7.1 channels? Also, can it be made to work at 24 bit and 96khz with all channels? Does this output contain all of the processing that that the analog outputs would normally have (such as 24 bit crystallizer and such), or is it output before that point?

Thanks for any info.

pjp · 28th January 2008, 03:24 PM

http://en.wikipedia.org/wiki/S/PDIF#...specifications

http://en.wikipedia.org/wiki/AES/EBU#The_Protocol

GestaltH · 28th January 2008, 08:32 PM

Thanks for the links. I didn't think to look up AES/EBU for more information.

So, it seems like it is limited to 2 channels and is either 20 or 24 bit. Is there a way to get a digital output for all 7.1 channels from a sound card like this? It doesn't have to be SPDIF necessarily.

JinMTVT · 30th January 2008, 02:18 PM

and i thought that digital output from computer cars
could carry the surround info..

i am pretty sure that i have seen many times
text about output of multiple channel output from digital
sound cards ???

GestaltH · 30th January 2008, 06:25 PM

I guess what I really meant was that it doesn't carry any more than 2 channels of uncompressed PCM data. It looks like you can get 5.1 (is 7.1 possible?) pass through on a digital connection but that is still encoded as Dolby Digital or DTS if I am understanding what I have read correctly.

What I was looking for a was uncompressed audio. The only interface that I could find that I liked that could do that is MADI (32 channels at 96k). ADAT lightpipe can also carry 8 channels but only at 48k and I was hoping for 96 or 192. In any case, both of those interfaces are found only on high end equipment (that I have seen anyways) and I don't know how I would go about actually retrieving the individual channel data from the stream anyways.

I still haven't really found a solution to what I'm trying to do. I'll probably make a post later that explains what that is and see if anyone has any ideas about how to implement it. If 8 channels of PCM 96k were available directly from the sound card, it would make what I was trying to do a lot easier.

In the mean time, if anyone has any information on low cost computer cards that support MADI or 7.1 channel PCM over SPDIF or AES, I would appreciate any information. Also, any info on "DIY possible" Dolby Digital or DTS decoding would be nice as well as info on MADI transmit/receive ICs if any exist.

JinMTVT · 30th January 2008, 08:58 PM

ah!!
that is better..u were suddently ruining all my plans

aahahah

good luck finding the right product for u then

pjp · 5th February 2008, 03:23 AM

So what is it you were trying to do ?

GestaltH · 5th February 2008, 05:11 AM

I have made a much more detailed post of what I was thinking here:

7.1 digital speaker idea

28th January 2008, 03:13 PM	#1
GestaltH diyAudio Member Join Date: Jan 2008	SPDIF and sound card question Hi, I am new to the whole DIY audio thing and have a few questions. I have a creative x-fi sound card with an SPDIF output. One question that I have is, does that output contain the signal for all 7.1 channels? Also, can it be made to work at 24 bit and 96khz with all channels? Does this output contain all of the processing that that the analog outputs would normally have (such as 24 bit crystallizer and such), or is it output before that point? Thanks for any info.

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28th January 2008, 03:24 PM	#2
pjp diyAudio Member Join Date: Nov 2006 Location: under the rainclouds	http://en.wikipedia.org/wiki/S/PDIF#...specifications http://en.wikipedia.org/wiki/AES/EBU#The_Protocol

28th January 2008, 08:32 PM	#3
GestaltH diyAudio Member Join Date: Jan 2008	Thanks for the links. I didn't think to look up AES/EBU for more information. So, it seems like it is limited to 2 channels and is either 20 or 24 bit. Is there a way to get a digital output for all 7.1 channels from a sound card like this? It doesn't have to be SPDIF necessarily.

30th January 2008, 02:18 PM	#4
JinMTVT diyAudio Member Join Date: Jul 2004 Location: MTL	and i thought that digital output from computer cars could carry the surround info.. i am pretty sure that i have seen many times text about output of multiple channel output from digital sound cards ???

30th January 2008, 06:25 PM	#5
GestaltH diyAudio Member Join Date: Jan 2008	I guess what I really meant was that it doesn't carry any more than 2 channels of uncompressed PCM data. It looks like you can get 5.1 (is 7.1 possible?) pass through on a digital connection but that is still encoded as Dolby Digital or DTS if I am understanding what I have read correctly. What I was looking for a was uncompressed audio. The only interface that I could find that I liked that could do that is MADI (32 channels at 96k). ADAT lightpipe can also carry 8 channels but only at 48k and I was hoping for 96 or 192. In any case, both of those interfaces are found only on high end equipment (that I have seen anyways) and I don't know how I would go about actually retrieving the individual channel data from the stream anyways. I still haven't really found a solution to what I'm trying to do. I'll probably make a post later that explains what that is and see if anyone has any ideas about how to implement it. If 8 channels of PCM 96k were available directly from the sound card, it would make what I was trying to do a lot easier. In the mean time, if anyone has any information on low cost computer cards that support MADI or 7.1 channel PCM over SPDIF or AES, I would appreciate any information. Also, any info on "DIY possible" Dolby Digital or DTS decoding would be nice as well as info on MADI transmit/receive ICs if any exist.

30th January 2008, 08:58 PM	#6
JinMTVT diyAudio Member Join Date: Jul 2004 Location: MTL	ah!! that is better..u were suddently ruining all my plans aahahah good luck finding the right product for u then

5th February 2008, 03:23 AM	#7
pjp diyAudio Member Join Date: Nov 2006 Location: under the rainclouds	So what is it you were trying to do ?

5th February 2008, 05:11 AM	#8
GestaltH diyAudio Member Join Date: Jan 2008	I have made a much more detailed post of what I was thinking here: 7.1 digital speaker idea

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