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Clock

I - Modes

Nothing would be happening without the Sardine clock. The clock is the central piece of the library. It is always running in the background and it manages function execution, recursion and timing. This is a complex and fragile mechanism. Python is particularly bad when you are trying to enforce timing guarantees. The clock is still a work in progress. If you are good at programming clocks or similar mechanisms, please come have a chat with me :)

The clock works pretty well until the moment it doesn't work anymore. If you are trying to be extra precise, follow these instructions:

  • kill every other non-essential program or process. We are trying to minimise context switching between the Sardine clock mechanism and the outside world.

  • start Sardine with sudo or administrator priviledges. This allows me to nice the process a fair bit. Sardine will have a higher priority among other processes.

  • be gentle, don't try to go faster than time. There is a minimal time division that the clock can handle. You can find out about it by typing c._get_tick_duration() a few times to see what the minimal amount of time between recursions is at your given tempo.

Internally, the Clock instance, aliased as c, is managing a lot of things. It is involved in proper message handling, ensuring time guarantees and much more.

A) MIDI Mode

a) Active

By default, the clock is running in active mode. It means that Sardine will emit a MIDI Clock signal on the default MIDI port. A MIDI Clock works by ticking constantly and it usually relies on a pulses per quarter note division, that indicates how many pulses form a basic rhythmic division. Hardware equipment are usually working at 24 or 48 PPQN but you can go much higher. Sardine tries to work well at these values, but the rest is really grey area. You are on your own.

b) Passive

In passive mode, Sardine will await for a clock signal. If the signal never comes, nothing will happen and you will be stuck in time. Please make sure to have a steady clock signal before booting Sardine. This mode is experimental and has never been truly tested.

Sardine can synchronise with other audio software / equipment through the Ableton Link protocol. You can switch from the regular clock to the Link clock by running the c.link() or c.unlink() method. Note that it is better to do this at startup and to shut down every running pattern before doing so because Sardine will dramatically jump in time. Some of your patterns might lie somewhere in the future, or somewhere in the past.

This synchronisation mode works reasonably well. Sardine has been tested live on stage multiple times with the Link synchronisation enabled and it was stable enough to run for several hours unmonitored :) Depending on your hardware, you might have to nudge some messages in time a fair bit but it has nothing to do with the synchronisation itself but more likely with how your system is handling messages (internal delay of some sort).

Log information

For your own curiosity, you can turn on clock monitoring by switching a boolean: c.debug = True. Be careful, the information is very invasive and it can be very fast. You will see how the clock advances in time by ticking at a steady rate. Please turn this mode off before playing anything because printing is not innocent, it can have a temporal cost that will cause the clock to slow down a little.

II - Attributes and useful information

  • c.beat: current beat.
  • c.phase: current phase.
  • c.ppqn: current pulses per quarter note.
  • c.tick: current tick.

III - Shifting / Latency

  • c._superdirt_nudge: adding a delay the timestamp attached to each SuperDirt message.
  • c._midi_nudge: nudging MIDI in time.
  • c.accel: acceleration of the clock, between 0 and 100%. Similar to a jog on a DJ controller.
  • c.nudge: nudging clock temporarily (for one cycle).