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Open standards for network audio streaming to local devices, Many closed-box solutions but any open-source? / uPNP recommendations?
post Apr 15 2012, 16:56
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Some years ago, I had a room mate who had an Airport Express, which we hooked up to the stereo in the living room so any of us could stream music from our own iTunes-compatible PC's. Needless to say, I absolutely fell in love with the functionality even though it meant I couldn't use fb2k for it. But since we don't live together anymore, i've been missing this kind of functionality at home. Also there were some things that were missing out on the Airport which I think could be done better.

I don't wanna mess around with buying cheap 10-meter cables every time the last one breaks, and having it lie across the living room whenever I want to listen to music from my laptop in my couch, or changing it over to my PC if I want to watch a movie or play a game from there, etc. Hope you get the picture. Having cables lying around the house is something i want less of.

There are, as mentioned before, commercial closed-box devices which have been engineered well and probably work really good. But they cost money and are all dependent on the manufacturer to think up and implement new features and improvements. They cost money for each receiver and, correct me if I'm wrong, do not have good cross-platform support. I have a Windows 7 PC for gaming, Ubuntu laptop for work, small Linux server for local media hosting, and my girlfriend has a Windows laptop. In the future, who knows, one of us might even get a smartphone or some other fancy network-capable device that would need hooking up to the sound system. Suffice to say, in such conditions a closed-source implementation is lacking in flexibility.

What about reciever devices? Currently they cost money for each receiver, based on a model of embedded devices which need their own power source, not possible to just install the capability on any network-enabled device with quality sound output capabilities. An open-source solution could open up the possibility to use virtually ANY device as a sound reciever.

Also I'd like to install my old amp/speakers in the kitchen and have the ability to change sound destination seamlessly to either location or both synchronously.
Because of the wish for playing video games and watching movies, the solution would have to be absolutely low-latency. Thanks to extreme bandwith and processing power available to us today cheap, I think it could be possible.

And maybe my always-on linux media hosting device could double as a networked media jukebox, in which guests of a party could connect to a web interface with their phones and enqueue a local mp3, stream music from their own device, or even enqueue a youtube music video? I'm talking quite some years down the road for this idea, of course.

Does anyone know if there are any projects to make this (or something similar) happen?
I once looked through the documentation of PulseAudio and think I understood that they support the capability for networked sound outputs but had such a hard time understanding the documentation that I never got as far as trying to hack something together. Maybe there are other audio server software implementations that could be willed into a similar configuration?
Are there perhaps cheap and partly open commercial solutions available that I haven't come accross? I have to admit, I haven't even spent that much time researching the subject, but a quick google search yields me nothing worth examining further, other than the commercial solutions and the pitfalls they have.

Maybe there's something I just haven't thought through here? Please, any ideas, criticisms, contributions, suggestions. I'm just posting this idea here to see if it makes any sense and to find out if anyone has had similar thoughts.

Thank you for reading smile.gif

edit: This is so embarrasing. I've completely glossed over implementing the features via UPnP.

This post has been edited by alive: Apr 15 2012, 17:05

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post Apr 16 2012, 10:38
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Well... I know you can set Pulse to certain bit depths and sampling rates as well as controlling the resampler quality. I challenge anyone to tell the difference between 44.1/16 pure and 44.1/16 up-sampled to 192/24 with a high quality sampler. However that's nice and CPU intensive, too. So in this case the biggest advantage to non-resampled sound over resampled sound would be the lowered CPU usage. All things considered, if the laptop is doing the heavy lifting that could be a major advantage.

I need to have a look at the specifications a bit more to see if the server or the client is in charge of the resampling. If it's the server I might have to rethink my use of a router and instead opt for something like an Atom based mini computer. To the test bench!

My current setup calls for the pulseaudio server to be used mostly for Youtube, Pandora and other kinds of things. I bought a Turtle Beach AudioTron for 20 bucks off of Craig's List a week or two ago for pure music listening mostly so I wouldn't have to have a computer open in front of me with its fan making noise and it's screen distracting me from my musical concentration and enjoyment. So far the AudioTron looks pretty cool but I haven't really had a chance to play with it a great deal owing mostly to the fact that it's a three prong outlet and I don't have one of those and I haven't had the chance to install a CGFI outlet yet. I will report more on the device once I'm done setting it up because it does have a lot of promise. Instead of relying on some funny quasi-standard like DLNA it uses the nice-and-easy NFS (network file system) standard which is dirt easy to implement on a network. It's only disadvantage is the only lossless codec it understands is WAV... which is a shame but I hear there are special NFS server thingies that can convert FLACs into WAVs on the fly but I haven't even begun to explore those yet. On the plus side, these "vintage" network audio players are DIRT cheap.

As for there not being enough bandwidth in 802.11g for streaming 44.1/16 audio or even 192/24 I highly doubt that! 802.11g was designed to provide up to 54Mbit/s through a theoretically perfect connection. Since we don't live in Faraday cadges we don't get anything near that but, off the top of my head, you can reasonably expect at least 5-7Mbit/s. Given that 192/24 audio, by my calculations 4.6Mbit/s uncompressed, and given that PulseAudio, to the best of my knowledge, uses some form of compression when networked I'd say it's plenty. That being said, network stability might be an issue in which case you might want to try increasing the Pulse server's buffer and/or improve your network hardware. A good way to improve the network hardware would be to invest in a good antenna. "Antenna rolling" 802.11g is really simple. I would suggest either buying a more powerful omnidirectional antenna or buying/making a directional antenna and pointing it appropriately.

By the way, my suggestion if a wireless router wasn't so much for the wireless but for the fact that custom firmware is much, much better developed for wireless products than wired products. You can always disable the radios and strip off the antennas if you so desire.

Oh, there's another possibility with regards to routers and music. You could attach the sound card to the router and then use a simple command line based music player to play music files directly using a Telnet or SSH terminal to control it. The only problem is that it would be a bit fussy but I could see maybe writing a nifty little plug-in or other front end for a personal computer to send the commands through the console to control it. Imagine: an open source Squeezebox for under 50 bucks, new!

Who said you had to be an audiophile tweako to have fun hacking your stereo system! laugh.gif
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