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Old 7th November 2001, 06:57 AM   #11
hifiZen is offline hifiZen  Canada
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Bluetooth is another wireless possibility. if i recall correctly, bluetooth should support enough bandwidth to fit 16/44.1 audio uncompressed! (download only - upload bandwidth is smaller, probably for power consumption reasons, since bluetooth is intended for portable applications). I'd have to look at the specs again, but I think bluetooth may also provide an isosynchronous data pipe option, much like USB or IEEE1394 (firewire). And, 802.11 may still be a good option, since it's bandwidth well exceeds what is required for 16/44.1. All you really need to watch for in an ethernet environment is that you don't have much other traffic causing congestion and screwing up your QoS. With sufficient breathing room, IP can deliver real-time data very well.
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Old 2nd December 2001, 08:45 AM   #12
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Default Audio bus

If real time is a requirement we'll never get there using compression.
The whole idea with compression is that you take a chunk and make it smaller. The compressor end needs to get that chunk, process it and send it, so when it reaches the receiver it's already not realtime - It doesn't care how fast you compress since you always have to get the chunk to have something to work on.
The smaller the chunks the closer to realtime, but real-realtime should be theoretically impossible I guess..

In this home-audio-bus application this should only be a problem when syncing with video, and probably the "chunks" can be small enough to make it work anyway. If not we'll need to delay the video to match.

As already stated, the bandwidth is the key.
Bluetooth is about 700kbit, so it should theoretically be able to carry five 128k streams. In real life it will be a lot less though, since there will be other BT devices around as well as good old interference.

How about a dedicated 10Mbit coax Ethernet?

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Old 7th December 2001, 08:42 PM   #13
hifiZen is offline hifiZen  Canada
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1394 / Firewire overcomes the real-time problem by using time codes and global clock syncronization through the interface. All this means is that you need to deliver the data slightly in advance so it can be prepared and buffered before it's scheduled playback time. 1394 includes so-called "isochronous" channels which allow for guaranteed delivery times and bandwidth, as well as priority over other network traffic...

Anyway, a really cheap way to go for DIY would be SPDIF/IEC958 over cat 5. Cat 5 has 4 twisted pairs, so you could pipe a full 8 channels of audio down one cable. The only thing is, since the characteristic impedence of cat5 isn't 75 ohms (I think its 120 or something around that value), then you need to make sure all your spdif receiver interfaces are properly terminated. The other alternative would be to include a small pulse transformer to match the impedences, but this also results in altered signal levels, so might not be a good way to go. Now, as far as distance and jitter levels are concerned, I really don't know. I suspect you could run several hundred feet without much trouble, but some form of jitter removal at each receiving unit would be a good idea.
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Old 7th December 2001, 09:00 PM   #14
Won is offline Won
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Mooze -

To state what you were suggesting more precisely, there is a tradeoff between compression ratios and processing latency, and this is dependent on "chunks" or block size (also, the number of blocks) that the algorithm uses to encoded the stream. This is an algorithmic latency; faster computers do not allow you to have less, only different algorithms.

However, it is certainly possible to have a compression algorithms (e.g. DPCM, MPEG Layer-1) that succeed at being "real-time," or within a particular latency-bound.

Just a few words from a software-ish guy.

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Old 12th January 2002, 08:07 PM   #15
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Here is one simple idea:

I use a very simple process. All my music is stored as 196kps MP3s, stored on my server. 100Mps Cat5 network w/ switch.
Each station uses a 200MHz minimum PC with sound card. I can push it or pull it, depending on the results I want.

It's not elegant, but very efficient. Up to four stations can actually listen to different playlists without any diminished capability.
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Old 22nd January 2002, 09:09 PM   #16
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I have heard good things about the Radio Shack 2.4GHz wireless video distribution system, working with SPDIF signals. I suppose you could buy multiple recievers and one transmitter, and transmit from wherever you want (eg CD player, computer, ect..).

Good luck



Quote:
Originally posted by knuckles_mctug
Hello everyone,

Hi, I been interested in audio electronics for a while and have only just come across this forum. I was wondering if there was a digital audio section. I'm interested in setting up a high bandwidth network to stream audio throughout my house and was wondering if anyone knew anything about it??
Thanks

Knuckles
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Old 10th September 2002, 02:46 PM   #17
Rarkov is offline Rarkov  England
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I am trying to design a wireless 5.1 system for my final year degree. hifiZen (Chad) mentioned Bluetooth which I think is a fantastic idea. You can get 5 chips (albeit Ball Grid Array) for $70 which is about 45 for us Brits! The 10m range is perfect for a theater system but it may well require 10 chips to get 'real-time' performance.

The Active Xover will be done in the Preamp before entering the Bluetooth Transceivers and a small amp in the speaker will make it totally moveable.

As you will note, the projects aren't identical - but we may be able to work together to get a Mid to Hi-fi wireless system.

I also agree that any suitable digital coding would be able to recreate a fairly accurate analogue signal at t'other end so digital transmission is just about a must! PCM coding is used frequently for Voice with 8k samples per second...Sounds fast - but no where near 44k or the likes!

Gaz
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Old 15th September 2002, 06:42 PM   #18
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a little expansion on ajames's idea;

it's a reasonably effective and cheap method to setup a machine (with ideally a reasonable processor and the biggest hard disk you can afford to store all the music) to serve audio as data (mp3's being the obvious example) to a few "bare-bones" client machines, especially if you have the know how to do it in linux - then the clients can be really low spec machines - you then don't really need much in the way of processing power, ram, etc because you can just leave out all the bells an whistles of a graphical operating system. they wouldn't even necessarily need a hard drive each and you can set them up to operate via just a keypad - no full keyboard or monitor necessary. then though, the "quality bottleneck" will be the soundcards that provide the audio line outs to whatever you're playing the music on.

as i was reading this i was wondering, what are the limitations of optical lines, in terms of distance, bandwidth, etc? you can get very high quality soundcards (with 24/96 converters, etc) that have optical and/or electrical digital in/out. BUT - how far can you run sp/dif or whatever without signal degradation?
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Old 16th September 2002, 08:35 PM   #19
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after that last post i had a look around; "Cajun" is described somewhere as an app for turning your pc into a "massive audio jukebox". you can find it here.
it can send audio to multiple "client" amps or whatever if you have a multi output soundcard.

this is the blurb from the website:

<snip>

CAJUN is a project to turn an old computer you might have kicking around into the centerpiece of your car or home audio system. CAJUN's features include:

Multiple stream support. If you have multiple sound cards in your computer, you can connect one to bedroom speakers, and one to your living room speakers. Each stream is separately controllable; i.e., each has its own set of keypads, infra-red controls, and LCD displays. (This feature is not likely to be useful in a car, unless you have a really long car :^)
Each stream has multi-device support, including: multiple input devices and multiple output devices (displays). Both the front seats and passengers in your minivan can see what's playing on their own display. All displays are updated at the same time.
All Displays can be any size - no limitations with multiple streams.
Display content is completely customizable. Different-sized displays can display different data.
Input and output devices may be connected and disconnected at any time. CAJUN continues to run.
Supports keypads, infra-red remote controls, LCD/VFD displays, FM cards, CD players, MPEG audio files, (WAV files+Ogg/Vorbis coming soon), Shoutcast/Icecast streams, etc.
An extension for invoking arbitrary Perl/Unix commands.
Easy-to-use, documented Perl API for writing new drivers.

<unsnip>
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Old 10th December 2002, 10:07 PM   #20
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has anyone else used a 2.4ghz video distobution system for SP/DIF? this is interesting to me because its already done! cool!
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