12:48 pm, 14 Feb 08
network audio between mac and linux, 2
(I wrote a previous post, but I posted it in the wrong place and it wasn't clear anyway. Sorry.)
Say I download an mp3* on my Linux laptop. I want it to play on the housewide speakers, which are connected to a Mac. What can I do that doesn't require me to use VNC or ssh?
sherm pointed out that iTunes is not a RAOP server in any case, so looking into free software implementations of that isn't useful.
To respond to some of the other suggestions: even if I had network file sharing set up (which is messy given that our IPs are assigned with DHCP, the laptop goes on and off the network, etc. etc.) or set up a streaming server, I still need some way of telling the Mac "start playing". That's why I was looking at "push" mechanisms for audio.
Looking over the options I considered, writing an OS X backend for PulseAudio is looking more promising.
* Try this one. It recently got stuck in my head, even though I first heard it months ago.
Say I download an mp3* on my Linux laptop. I want it to play on the housewide speakers, which are connected to a Mac. What can I do that doesn't require me to use VNC or ssh?
sherm pointed out that iTunes is not a RAOP server in any case, so looking into free software implementations of that isn't useful.To respond to some of the other suggestions: even if I had network file sharing set up (which is messy given that our IPs are assigned with DHCP, the laptop goes on and off the network, etc. etc.) or set up a streaming server, I still need some way of telling the Mac "start playing". That's why I was looking at "push" mechanisms for audio.
Looking over the options I considered, writing an OS X backend for PulseAudio is looking more promising.
* Try this one. It recently got stuck in my head, even though I first heard it months ago.
I was just about to reply to your previous entry that writing an OS X backend to PulseAudio would probably be the most rewarding approach if you're going to have to develop something.
However, I note also that PulseAudio can talk to esd and there is an esd port for OS X 10.5. It seems that also someone has been crazy enough to implement an esd server in Java. I've no idea how well esd performs over a network -- presumably not too well, or else PulseAudio wouldn't be replacing it -- but perhaps it's worth a try.
Streaming audio
FWIW, "Uncompressed" audio isn't exactly high bit rate compared with most computer networks (wireless or otherwise). For instance CD audio (which is also uncompressed) is around 150 KB/s (see eg, Wikipedia), which is around 1.4 Mbps. Pretty low compared with a 10/100/1000 Mb/s network, and still low compared with a 11Mbps or 54Mbps wireless lan. Even doubling the sampling rate (eg 96 Khz sampled audio, rather than 44.1 KHz sampled audio for a CD) is well within the range of a data network.Things like the Squeezebox will stream uncompressed audio for any format that it doesn't natively understand (anything except MP3 I think), and they seem to play back just fine. So you're unlikely to have a problem unless your wireless lan is subject to a lot of interference -- in which case you're more likely to get dropouts with anything you choose than audio loss due to the bandwidth used.
Ewen
I wrote up what I'm currently using to play mp3s wirelessly to my speakers via a Nokia 770 here. That uses pulseaudio on the sending side (allowing me to use all my existing MP3 apps, including the brilliant JuK) and esd on the receiving side (mainly because the N770 doesn't have a pulseaudio port).
Bandwidth isn't a problem; uncompressed 22khz audio streams are pretty low-bandwidth.
Of course, pulseaudio and the music player daemon work well together.
mpd means I have to set up network file sharing as well as reindexing whenever I have a new file I want to play. And it doesn't work when I (e.g.) play audio through YouTube.
Unless OSX audio is *really* odd, it shouldn't be terribly much work to write a backend for it -- the code is rather modular, and already has at least three backends to various OS audio APIs -- win32, oss, and alsa.
Anyway, you have to either get the mpd to play files off the network -- which it can do directly from http, BTW -- or you can do what I do, and play random things from whereever is convient, getting them to your speakers with pulseaudio, and play your music library from mpd.
http://developer.apple.com/documentation/MusicAudio/Conceptual/AudioQueueProgrammingGuide/Introduction/chapter_1_section_1.html
"DisOrder is a software jukebox designed for multi-user environments. It allows users to pick music tracks for play from a shared collection. When nobody has picked anything, it can play randomly picked tracks instead.
"Sound can be played via either the ALSA or OSS (/dev/audio) interfaces; via the Mac's native sound API; or broadcast/multicast over a LAN.
"Natively, DisOrder supports MP3, OGG, WAV and FLAC files. It's possible to add players for other file formats."