[Tfug] Audio client

[Harry McGregor]

Hi,

Bexley Hall wrote:
> 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.
>
>   
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 onto solid, even with
solid rated (smokey) RJ45 plugs, it's just never as reliable as 110
punch downs.
>>> - ~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)
>
>   
I can under stand that, though it's not much bandwidth for a 100mbit
network.
>> 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.

>>> 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.
>   

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.

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.

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.
> 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.

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

                         Harry
>> 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...
>
>
>       
>
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