Remote performance via zeromq
I did a remote performance streamed to Barcelona last week as part of a “Perspectives on multichannel live coding” concert, which involved me sitting on my studio floor in Sheffield, live coding broken techno for 16 speakers. The music was beamed over to an audience of 30-40 people in Universitat Pompeu Fabra, who were surrounded by 16 speakers, while I created the music locally, monitoring in quadrophonic surround sound (sadly I didn’t have 16 speakers to hand). I really enjoyed the challenge of making a coherent multi-channel performance, and got some positive feedback on the music, but thought I’d share the more technical side..
The organiser/curator Gerard Roma and I discussed the possibility of streaming audio, compressed with ogg vorbis and streamed over icecast. Encoding/decoding and streaming 16 channels of audio is a bit problematic though, we probably had the bandwidth but the libraries just aren’t there with 16 channel support. It’s straightforward to stream 4 channels, or 5.1, but for some reason every channel has to be labelled with a location, and I couldn’t get sixteen channels working with gstreamer.
In any case streaming synth control messages rather than audio output is a better approach really, and that’s what we went with. I just ran my synthesiser Dirt in both places, and sent trigger messages over Open Sound Control to both. Unfortunately it wasn’t quite that simple due to the various institutional firewalls between us, so I sent the OSC over ZeroMQ. This involved running a simple daemon on my (unfirewalled) server, which received OSC over plain UDP, which it forwarded to any ZeroMQ subscribers. It was then easy to add some code to Dirt which subscribed to the ZeroMQ server, and piped OSC messages into liblo for processing. Using ZeroMQ as part of this made for really easy to write, fault-tolerant code.
A slightly amusing side effect is that anyone running a recent git checkout of Dirt during my various tests and performance would have received my OSC messages and heard me mess around and play.. Something that could be made more of in the future…
I’d love to do more multichannel performances, streamed or in person, let me know if you’d like me to propose something for your system!