3  The RT Engine

The main purpose of the RT Engine is to receive <realtime> objects and provide ways to control exactly when a <realtime> objects processing function is being called. The API for doing this is hidden from the user, and is accessed by calling methods in the <realtime> class.

3.1  Features

• Realtime safe

• Jack driver

• Unlimited number of input and outputs

• The RT Engine is a class, and unlimited number of <RT-Engine>-instances can run simultaneously. ¹

• Protection mechanism provided to avoid locking up the computer when using too much CPU.

• Properly made priority queue system for events to ensure a stable CPU load (At least, I hope so).

• Controlled entirely from scheme using Guile

3.2  Guile Functions to control the Realtime Engine

(rte-pause)

   
Pause the engine.

(rte-continue)

   
Starts running the engine after being paused.

(rte-restart #:key num-input-ports num-output-ports)

   
Stops and starts engine. If you only have stuck sounds, use (rte-silence!) instead. (Warning, theres a huge memory-leak when using this function.)

(rte-silence!)

   
Call this function if you have stuck sounds or <realtime> instances running. (This function is equivilant to the freeAll OSC message for Supercollider3)

(rte-time)

   
Returns the time in seconds since the engine was started.
(rte-time) = (rte-frames) / (rte-samplerate)

(rte-samplerate)

   
Returns the samplerate.

(rte-frames)

   
Returns the number of frames since the engine was started.

(rte-is-running?)

   
Returns true if engine is running. (Ie. not paused)

(rte-max-cpu-usage)

   
This is a setter-function. The engine will stop calling further <realtime> instances if the cpu-usage for the jack client is higher than (rte-max-cpu-usage). This is a safety mechanism to avoid locking up the computer or jack to kill the client, which can be unfortunate or embarrassing in certain situations. Note however that if exactly 1 <realtime> instance is using too much cpu, this mechanism will not work. The default value is set to 80. At least on my machine, this is a comfortable value, because the machine is still quite responsive at 80%.

(rte-info)

   
Returns a list of 7 elements:

1. Current size of the priority queue.

2. Size of the priority queue.

3. Number of lost events because the priority queue was full.

4. Number of events waiting to be run.

5. Number of <realtime> instances currently running.

6. CPU load reported by the jack client.

7. Number of times the execution of <realtime> instances have been stopped because the cpu-usage was higher than (rte-max-cpu-usage). This number is mostly useful when being compared to a previous value, or to check whether its higher than 0.

3.3  Global variables

*rt-engine*

The main object, an instance of <rt-engine>. Evaluate (-> *rt-engine* dir) to get the name of all the methods and subclasses.

*rt-num-input-ports*

Number of input jack ports. You can define this variable before loading rt-compiler.scm or rt-engine.scm to override the default value of 8.

*rt-num-output-ports*

Number of output jack ports. You can define this variable before loading rt-compiler.scm or rt-engine.scm to override the default value of 8.

*out-bus*

The bus connected to the soundcard output.

*in-bus*

The bus connected to the soundcard input.