[lug] Ethernet sound card - digital solution

[D. Stimits]

John Dollison wrote:
> Something I completely forgot about....
> Many modern sound cards have Dolby 5.1 surround sound, and include a digital
> output channel.  That digital signal can be hooked up to the input of most
> modern stereo systems.  Since it's all digital, from hard drive to stereo
> system, there should be 0.0% signal loss and distortion.

Most people don't realize that the S/PDIF in/out is a serial standard 
that works both in optical and copper, depending on the connector. I 
don't know what the length restrictions are for copper, or cable 
characteristics, but it is a digital serial. On the other hand, some 
sound equipment accepts "lossy" compressions (though very hard to 
hear...far less than typical analog problems), such as mini-disk 
portable records, but others use lossless (full size equipment, but it 
is compatible to mix). Optical would be too expensive to wire a house 
with, but if copper had a reasonable house wiring length possibility, it 
just might do the job, and it could deal with 5.1 if the hardware on 
both ends could. In that case, loss would be related only to whether 
lossy or lossless compressions were used by the hardware at the ends (in 
the case of lossy, I think this is only during record, playback is of 
course irrelevant, decompression doesn't care). Connectors that fit with 
standard cables (patch cables between perhaps a home theater and a 
minidisk) are about $15 each, but vary a lot in price.

D. Stimits, stimits AT attbi.com

> 
> John D
> 
> .
> ----- Original Message -----
> From: "Peter Hutnick" <peter-lists at hutnick.com>
> To: <lug at lug.boulder.co.us>
> Sent: Thursday, September 05, 2002 6:20 PM
> Subject: [lug] Ethernet sound card
> 
> 
> I've been knocking a (possibly stupid) idea around in my head.  Like every
> other Joe in town I want to be able to get music from my PC to my stereo.
> I'm not real satisfied with any of the obvious solutions.  I think that
> there is a better way.
> 
> Obvious ways and their problems:
> 
> 1. Plug sound card output into stereo.
>  - Less than ideal quality
>  - Very limited distance between the PC and the stereo
> 
> 2. USB "sound card"
>  - Not much better run length
>  - Not cheap >a buck and a quarter
> 
> 3. Component MP3 player
>  - expensive
>  - limited to codecs/data rates/processing power of the box (or serious
> hacking)
>  - limited storage (yes, many are hackable)
>    OR
>  - tied to "server software" on a PC
> 
> 
> My idea is to build something similar to a USB sound card, but use
> Ethernet as the interface.
> 
> Something like:
> 
>  You play a song on the PC with your favorite player. (This could be as
> simple as cating a file to the appropriate device file.)
>  The sound driver breaks the audio down into chunks of a fixed size, wraps
> an Ethernet frame around it (with the appropriate MAC) and flings them
> onto the wire (at a fixed rate).
>  The "sound card" grabs all packets with its MAC off the wire (I think
> that this description is technically faulty, but it gets the point
> across), strips the Ethernet frame and dumps the data into a FIFO.
>  The FIFO streams into a DAC, which terminates into a pair of RCAs.
>  If there is a stereo on the other end of the RCAs you get sound!
> 
> I am well aware that I have glossed over some non-trivial stuff here . . .
> that's why I'm writing to the list!  Is anybody and EE type that can tell
> me what the big problems with this are?  Is getting the data out of the
> Ethernet controller and into a buffer feasible without using a processor?
> If so I think that this could be build cheap around a DAC out of a broken
> CD player!
> 
> -Peter
> 
> 
> _______________________________________________
> Web Page:  http://lug.boulder.co.us
> Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
> Join us on IRC: lug.boulder.co.us port=6667 channel=#colug
> 
> _______________________________________________
> Web Page:  http://lug.boulder.co.us
> Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
> Join us on IRC: lug.boulder.co.us port=6667 channel=#colug
>