[Tfug] Audio client

[Bexley Hall]

Hi Harry,

> > - 10/100 interface
>   
> I would recommend both an RJ45 and a 110 punch block. 
> RJ45 for patch cables, and 110 for inwall installation.

Hmmm... I'll have to look at if I can fit both on the
board without increasing its size (i.e., install one or
the other).  I want this to be *really* small.

> > - ~64KB RAM
> > - ~128KB Flash
> > - dual 24 bit D/AC's
> > - ~10W stereo amplifier (1x10 or 2x5)
> > - PoE
>   
> 802.3af or some hack job?

> > - "line out" at the expense of amplified output
> >
> > Note there is *no* user interface!  The goal is to make the
> > audio gear in the house "become invisible" (so why design a
> > box with a display and controls that will then need to be
> > *visible* in order to be usable??).  This also greatly reduces
> > cost (I'm probably in the $25 range for "one off" quantities)
> > and size (ideally, I can build this *into* a speaker and
> > never have to see any of it!)
> >
> > My plan is to use a simple codec and (in my case) convert all
> > of the media files to that form so they can be served directly.
> > Or, write a transcoder that resides server-side and effectively
> > does the same thing.
>
> 10/100 has lots of bandwidth, just use PCM/WAV, no need for
> compression.

Recall that you might end up having several different streams 
running at the same time.  Uncompressed you need ~180KB/s
so 2 or 3 streams can eat up a big chunk of a 10Mb/s link.
(i.e., if fed through a *hub* or from a single 10BaseT NIC)

> You don't have to transcode, just "play" the file, as your
> target is uncompressed audio.

Yes, but only if you *don't* use a codec.

> Even 24bit 96Khz audio is under 5mbit/sec
> 
> More "normal" / CD quality audio is 16bit 48KHz and is
> about 1.5Mbit/sec
> 
> Both of these should easily fit on 10/100 ethernet.

Yes.  But see above.  Remember, you may also have other traffic
Re: your other post... the transcoder can sit above the
"virtual" sound card so it transparently makes the card 
"look" like a regular card yet deliver packets in whatever
form needed.

> > Note that simplifying the client also makes it easier for people
> > to hack the box -- since you can hack the server side instead of
> > having to deal with the actual target (cross development, etc.)
> >
> > And, it lets folks decide how *they* want to talk to the box
> > instead of living with someone else's (e.g., me) idea of what 
> > a user interface should entail.
> >
> > Of course, this also means people will have to make an
> > *investment* (time) in that -- instead of just buying it off
> > the shelf!  :>  (Free software, not free lunches!)
>
> Sounds very cool, we did a bunch of work with the Channel
> Vision's A-Bus products.
> 
> Worked quite well, but very expensive.
> 
> Having the low power amp in the face plate was great. 
> Wired speakers to the wall plate in the room, and not back to a wiring
> closet.  Speaker wire adds up quickly, cat 5 is cheap.

Yes.  And it adds to clutter if you have to have separate
power, signal and network cables.  This is a big incentive for
making the thing small and inexpensive -- once it starts
suffering from feeping creaturism, then it gets expensive
and you want to have one handle 2, 4, 5.1, 7.1, etc. speakers.
This also means needing more power, bigger amplifiers, running
cables across the floor, etc.

OTOH, if you can keep it simple and small, you can afford
to "waste" half of a "stereo" unit to gain the advantage
of not having other wires to contend with

> These units use Cat-5 to the unit, and have both an RJ45
> and a 110 block.
> 
> http://www.hometech.com/hts/products/audio/whole_house/cv_abus/index.html

Thanks!  I'll have a look...