6 Nov
2004
6 Nov
'04
4:08 a.m.
On Sat, Nov 06, 2004 at 08:55:18 +0100, Jens M Andreasen wrote:
run_synth*() are the ones that supports MIDI, they take a snd_seq_event_t *
parameter which are ALSA seq structs timestamped against the current
audio buffer.
The interface is explained in dssi.h, around line 223:
/**
* run_synth()
*
* This member is a function pointer that runs a synth for a
* block. This is identical in function to the LADSPA run()
* function, except that it also supplies events to the synth.
*
* A plugin may provide this function, run_multiple_synths() (see
* below), both, or neither (if it is not in fact a synth). A
* plugin that does not provide this function must set this member
* to NULL. Authors of synth plugins are encouraged to provide
* this function if at all possible.
*
* The Events pointer points to a block of EventCount ALSA
* sequencer events, which is used to communicate MIDI and related
* events to the synth. Each event is timestamped relative to the
* start of the block, (mis)using the ALSA "tick time" field as a
* frame count. The host is responsible for ensuring that events
* with differing timestamps are already ordered by time.
*
* See also the notes on activation, port connection etc in
* ladpsa.h, in the context of the LADSPA run() function.
*
* Note Events
* ~~~~~~~~~~~
* There are two minor requirements aimed at making the plugin
* writer's life as simple as possible:
*
* 1. A host must never send events of type SND_SEQ_EVENT_NOTE.
* Notes should always be sent as separate SND_SEQ_EVENT_NOTE_ON
* and NOTE_OFF events. A plugin should discard any one-point
* NOTE events it sees.
*
* 2. A host must not attempt to switch notes off by sending
* zero-velocity NOTE_ON events. It should always send true
* NOTE_OFFs. It is the host's responsibility to remap events in
* cases where an external MIDI source has sent it zero-velocity
* NOTE_ONs.
*
* Bank and Program Events
* ~~~~~~~~~~~~~~~~~~~~~~~
* Hosts must map MIDI Bank Select MSB and LSB (0 and 32)
* controllers and MIDI Program Change events onto the banks and
* programs specified by the plugin, using the DSSI select_program
* call. No host should ever deliver a program change or bank
* select controller to a plugin via run_synth.
*/
void (*run_synth)(LADSPA_Handle Instance,
unsigned long SampleCount,
snd_seq_event_t *Events,
unsigned long EventCount);
- Steve
5.3. Audio
class
The remaining functions belong to the audio class:
-- run()
-- run_adding()
...
...
I understand from the naming what these callbacks will do, but I guess
that run() takes parameters, no? Possibly a pointer to a struct that the
synth itself supplied, right? I have a hard time though, guessing where
the note on/off and external controllers come in to play