Gibberwocky for Max websocket protocol

Gibberwocky for Max websocket protocol

Gibberwocky communicates with Max using a websocket protocol outlined here. Theoretically any other client should also be able to interface with Max using this same websocket protocol. (And vice versa, alternate gibberwocky hosts could implement with clients using this protocol.)

Timing

Every time the Max transport advances a beat, the gibberwocky object sends a request to clients for the subsequent beat's events. For example, on beat 3, gibberwocky will send a request for all events that should occur during beat 4. This one beat of latency ensures that all messages arrive with plenty of time to spare.

Read more about the project here: http://homes.create.aau.dk/dano/nime17/papers/0024/paper0024.pdf

What the client (browser) sends to Max:

Messages are sent as regular strings with spaces for arguments. Multiple messages can be packed into a single packet send by delimiting with the "|" bar symbol.

Most messages are prefixed with timing info for scheduling in the future (the add <time> prefix). The time parameter here is a floating point value measured in the underlying pulse, or beats, of Max's global transport. So, for example, to schedule an event half-way through the 2nd beat of the bar, prefix the event message with add 2.5 . Note that Max counts pulse/beat values from 1. In any case, for most cases the integer portion of the <time> argument should be the same value as received by the seq <time> message described below.

Note: the add <time> prefix is optional. If ommitted, the message will be executed as soon as it arrives (subject to unpredictable network and processing latencies). For example, to send a MIDI note immediately use midinote <pitch> <velocity> <duration> instead of add <time> midinote <pitch> <velocity> <duration>.

Global

get_scene -- requests Gibberwocky to inspect the patcher's available modulation points. The response will be a stringified JSON dictionary (described below). Typically send this message when the client connects to Gibberwocky.

Scripting-name messages ("parameters")

add <time> set <name> <message...>

sends a message to any valid object via its scripting name (via pattrforward)

• name: the valid scripting name / pattr path of the target object
• message: one or more arguments (space delimited) that forms the message sent

E.g. add 2.5 set live.dial 74 means at time 2.5 beats send the message 74 to the max object named live.dial.

E.g. set amxd~ snare-decay 300 means immediately send the message snare-decay 300 to the max object named amxd~.

MIDI notes

add <time> midinote <name> <pitch> <velocity> <duration>

triggers a MIDI note on a device in the patcher.

• name: the scripting name of the device
• pitch, velocity: MIDI values in 0-127
• duration: in milliseconds

E.g. add 1 midinote drums 42 127 500 schedules a midinote at beat 1.0 on the device named "drums" with pitch 42, velocity 127, and duration 500ms.

Signals

Messages to control the audio signal outlets of gibberwocky use the sig prefix, followed by an index number, where the first signal outlet is index 0, etc.

add <time> sig <index> expr <genexpr>

defines a new signal modulation for one of the gibberwocky signal outlets.

• index: the signal outlet index, where the first signal outlet is 0, the second is 1, etc.
• genexpr: a string of valid GenExpr code (see documentation) which defines one output (e.g. out1=0.5;).

E.g. add 3.5 sig 0 expr "Param p0(5); out1=cycle(p0);" will assign a 5Hz oscillator to the first signal outlet of gibberwocky at time 3.5 beats.

add <time> sig <index> param <name> <value>

changes a param defined in the genexpr.

• index: as above
• name: the name of the param object in the genexpr.
• value: the new value for this param

E.g. add 1.0 sig 0 param p0 13 will set the param p0 of the signal graph in the first signal outlet of gibberwocky to a value of 13, at the time 1.0 beats.

add <time> sig <index> clear

removes the genexpr, but holds the last output signal value as a constant

• index: as above

add <time> sig <index> zero

removes the genexpr, and sets the output value to zero

• index: as above

Generic messages

add <time> <message...>

Any other messages received that do not match get_scene, set, midinote, or sig will be forwarded to the first outlet of the gibberwocky object for handling in the patcher.

What Max sends to the client:

The scene

In response to a get_scene message, gibberwocky will send a representation of addressable parts of the Max patcher to all connected clients. This will also be updated and sent whenever the patcher is saved. The scene is sent as a stringified JSON object, which can be turned into a Javascript object via JSON.parse(scene).

A quick way of detecting this message is to check if the message's first character is "{" curly parenthesis.

Timing

seq <beat>

This message is sent on every beat, and is a request for clients to reply with all events to occur within the specified beat. See the explanation of timing above.

Other messages are for information only and do not expect responses:

ply <N> -- the play state, either 1 (playing) or 0 (stopped)

bit <N> -- the current beat

bar <N> -- the current bar

bpm <N> -- the current BPM

sig <S> -- the current time signature

Feedback

err <message...>

errors posted to the Max window will also be sent to clients here.

snapshot <index> <value> <index> <value>...

a representation of the current values of the gibberwocky signal outlets. The list is also space-delimited, and comes in pairs of signal index and signal value. This is useful for providing visual feedback of signal modulations within clients.

E.g. snapshot 0 0.5 1 0.1234 2 0.74