[Tfug] Audio client

[Bexley Hall]

Hi Harry,

> > 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.
>   
> If you can't fit both, I would go 110, as you intend this
> to be more of a hidden, in wall type device.  I *hate* crimping 

Actually, I was looking at it the other way 'round -- bolt it onto
the back of a bookshelf speaker (or, slip it inside the enclosure
if the back can be removed -- not gllued on -- without damaging
it cosmetically) and then just sit the speaker where you want it.

I.e., consider speakers from a small "integrated" bookshelf
stereo that are currently tethered to that stereo with cables.
Get rid of the stereo.  Put the speakers where you want them.
Then just plug them into a CAT5 PoE drop (i.e., the CAT5
cable takes the place -- cosmetically -- of the "speaker cable")

> onto solid, even with solid rated (smokey) RJ45 plugs, it's just 
> never as reliable as 110 punch downs.

Hmmm... I will have to look into that.  Moving power over the 
connector makes this a bit more critical.

Though, as I read my arguments, here (and yours), it occurs to
me that I should also consider a USB host port implementation.
And, a connector for an external power supply.  The MCU's I
have been looking at have lots of I/O that I am not using
(including USB).  The USB connector could be colocated with
the RJ45 (i.e., populate the board with one or the other).
It's purpose would be to allow you to plug in a wireless
USB dongle!  I.e., wired network gets replaced with *wireless*.
Then, you no longer have PoE available so you need an external
power supply (wall wart/brick) to power everything.

This gives you a whole different way of using the device
(wireless stereo/speakers)

> >> 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)
>
> I can under stand that, though it's not much bandwidth for
> a 100mbit network.

Yes.  My original idea was to do exactly this (AIFF, etc.).
But, the processors that are available with the right
bits of onboard I/O have *way* too much horsepower.  So,
I can "waste" some of that on a codec.  I am also thinking
that some small amount of signal conditioning could be done
in the processor (e.g., tone controls, programmable delay,
etc.).

The point is *not* to try to support all these silly formats
that keep coming up.  Pick one (or *make* one) and then push
all of the conversion into the host/server.  Folks like me
can just one-time convert their entire music library.  Folks
who want to stream audio from internet sources would need a
transcoder,e tc.

> >> 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.
>
> If you put it behind the virtual sound card, then you only
> have to worry about one codec, and you can use a patent safe 
> codec such as Ogg Vorbis.

Exactly.  I don't want to commercialize this.  I'd rather just
order a bunch of extra boards and let folks assemble their own
and take it whichever direction they want.  OTOH, if you just
give people a board and a schematic, few folks have the capability
to "build from scratch" a real system.

> >> Sounds very cool, we did a bunch of work with the Channel
> >> Vision's A-Bus products.
> >>
> >> Worked quite well, but very expensive.

I couldn't find the modules you were talking about at the URL.
There were some "big boxes" that seemed to do stuff like that
but I was assuming you were talking about something *small*
(i.e., fits in a 1G JBOX)

> >> 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.
> 
> The low power amp was fed power over the CAT-5 (non ethernet, just
> cat-5), and so all you have is the speaker (left and right) and the
> Cat-5 connection.

Ah, OK.

> If you put the complexity in the virtual sound card....  Let's say you
> have 8 of these gadgets, you could put 6 of them together to get a 5.1
> system, and the virtual sound card would be able to address them as
> parts of a 5.1 system.  The other 2 could be used as a single channel on
> each as part of a more spread out stereo sound card.

Yes.  There are other extensions as well.  E.g., you could apply
this in a VERY LARGE (outdoor) setting (esp. if you do the
wireless trick) and deploy each box at varying distances from
the stage.  You then deliberately introduce a delay in the
signal path that is proportional to distance from stage / speed 
of sound so that the sound emitted from "this" speaker is
coincident with the acoustic wave arriving from the speaker(s)
closer to the stage.

(I've been to concerts where this was done with wired audio
distribution and programmable delay lines)

However, you have to be able to synchronize the audio streams
between each of these nodes and fully characterize the performance
of your network stack.  This is a problem that doesn't exist when
you process all of the audio in *one* box.

> That would be very nifty.
> 
> I would use a jumper or dip switch on the device to select
> single or dual channel operation.  The device would report what
> it was capable of to the driver over the TCP/IP connection.

Hmmm... I would have to think on this.  I dislike jumpers as
they are things that people can screw up.  I will have to look
at the audio amp selections and see if I can garner any information
from the amplifier "at run time" that lets me determine what
sort of a load I have.

> > 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
>
> That is a great concept for this.  I am thinking of a device that you
> can combine with fire rated heat shrink, run your cat-5 to it, and then
> run a short length of speaker cable from it to the speaker(s), heat
> shrink it, and leave it in the ceiling next to the speaker.

That was one of the initial motivators I had for this.  But, our
ceilings here would cook speakers (flat roof so ceiling == roof).
Screwwy way to build things!  :<

> In-wall speakers are getting very cheap:
> 
> $43 for a pair:
> http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10837&cs_id=1083701&p_id=4102&seq=1&format=2
> 
> http://www.monoprice.com/products/subdepartment.asp?c_id=108&cp_id=10837

Hmmm... how deep are these (I will chase the link after SEND)?
I have been looking at very small wall *mounted* speakers (i.e.,
they hang off the wall) for places where floor standing speakers
would be problematic (e.g., kitchen, family room).  Depending on
cosmetics, putting something *in* the wall might be preferable.