ALSA SEQUENCER DRIVER

The resolution of real-time value is in nano second. The followed events will be processed in real-time without queued. A typical usage is the MIDI patch-bay. In the API, the skew is defined by two values, the skew base and the skew value. One of the new features in ALSA sequencer system is subscription of ports.

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OSS Sequencer Emulation on ALSA — The Linux Kernel + documentation

When the event arrives at the queue it is normalized to absolute format. The latter port does not receive messages but supports subscription.

On the scheduling mode, an event is once stored on the priority queue and delivered later or even immediately to the destination, whereas on the direct dispatch mode, an event is passed to the destination without any queue. These two queues are bound together to work synchronously.

Creates a new handle and opens a connection to the kernel sequencer interface. This whole library does not seem sequencee be particlarly thread aware.

It is useful to avoid unexpected disconnection. The time stored in an event record is a union of these two different time values.

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Basically, subscription means the connection between two arbitrary ports.

Documentation

On the other hand, the latter is passed without using memory pool. String The sequencer’s “name”. In the real-time mode, all lasa are dispatched immediately. Get identifier of a sequencer handle. The close callback is called when this device is closed by the application. The addr contains the address of ALSA sequencer port which is assigned to this device.

Typically, the open callback does the following procedure:. When an event is passed to sequencer from sequener client, sequencer fills source. This depends on the following methods of the SequencerEvent class: Default value is 0.

The library buffer can be controlled using the methods MidiClient:: The source and destination addresses are like the below.

The received timer events are broadcasted to all subscribed clients. The ports which won’t accept subscription should have this capability for better security.

The callback should turn off the sounds on the relevant port immediately, and initialize the status of alss port. Round-off errors can be neglected. The timestamp of the event can either specified in real time or in song ticks. A typical code would be like below:.

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alsa-seq: Binding to the ALSA Library API (MIDI sequencer).

You must also use the method MidiClient:: Once seqkencer a apsa is created, the two queues are associated to that queue record in fact: The sender must set this value as the destination client.

At beginning, this module probes all the MIDI ports which have been already connected to the sequencer. You can make the queue faster or slower by setting the skew value bigger or smaller. After a client is closed, an event with ClientExit is broadcast to announce port.

The resolution of real-time value is in nano second. Closes the sequencer client and releases its resources.

The third method involves signals and slots. The source and dest fields are source and destination addresses.

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