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authorDavid Robillard <d@drobilla.net>2008-01-21 15:14:53 +0000
committerDavid Robillard <d@drobilla.net>2008-01-21 15:14:53 +0000
commitd6b87aa26ef482a8952437f7472b81a2240f01fd (patch)
tree620d233b902c78413dc17ee5f921633251239695 /src/common/lv2ext/lv2-midiport.h
parent2356f96fbd6c9d70dedcd0d64bf0d72786ea36bb (diff)
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Work on generic LV2 events.
git-svn-id: http://svn.drobilla.net/lad/ingen@1090 a436a847-0d15-0410-975c-d299462d15a1
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-/****************************************************************************
-
- lv2-midiport.h - header file for using MIDI in LV2 plugins
-
- Copyright (C) 2006 Lars Luthman <lars.luthman@gmail.com>
-
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
- (at your option) any later version.
-
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 01222-1307 USA
-
-****************************************************************************/
-
-#include <stdint.h>
-
-/** @file
- This file contains the specification for an LV2 MIDI port extension.
-*/
-
-#ifndef LV2_MIDIPORT_H
-#define LV2_MIDIPORT_H
-
-
-/** This data structure is used to contain the MIDI events for one run()
- cycle. The port buffer for an LV2 port of the type
- <http://ll-plugins.nongnu.org/lv2/ext/MidiPort> should be a pointer
- to an instance of this struct.
-
- To store two Note On events on MIDI channel 0 in a buffer, with timestamps
- 12 and 35.5, you could use something like this code (assuming that
- midi_data is a variable of type LV2_MIDI):
- @code
-
- uint32_t buffer_offset = 0;
- *(double*)(midi_data->data + buffer_offset) = 12;
- buffer_offset += sizeof(double);
- *(uint32_t*)(midi_data->data + buffer_offset) = 3;
- buffer_offset += sizeof(uint32_t);
- midi_data->data[buffer_offset++] = 0x90;
- midi_data->data[buffer_offset++] = 0x48;
- midi_data->data[buffer_offset++] = 0x64;
- ++midi_data->event_count;
-
- *(double*)(midi_data->data + buffer_offset) = 35.5;
- buffer_offset += sizeof(double);
- *(uint32_t*)(midi_data->data + buffer_offset) = 3;
- buffer_offset += sizeof(uint32_t);
- midi_data->data[buffer_offset++] = 0x90;
- midi_data->data[buffer_offset++] = 0x55;
- midi_data->data[buffer_offset++] = 0x64;
- ++midi_data->event_count;
-
- midi_data->size = buffer_offset;
-
- @endcode
-
- This would be done by the host in the case of an input port, and by the
- plugin in the case of an output port. Whoever is writing events to the
- buffer must also take care not to exceed the capacity of the data buffer.
-
- To read events from a buffer, you could do something like this:
- @code
-
- uint32_t buffer_offset = 0;
- uint32_t i;
- for (i = 0; i < midi_data->event_count; ++i) {
- double timestamp = *(double*)(midi_data->data + buffer_offset);
- buffer_offset += sizeof(double);
- uint32_t size = *(uint32_t*)(midi_data->data + buffer_offset);
- buffer_offset += sizeof(uint32_t);
- do_something_with_event(timestamp, size,
- midi_data->data + buffer_offset);
- buffer_offset += size;
- }
-
- @endcode
-
- If you think this looks like too much code to simply read and write MIDI
- events, take a look at the helper functions in lv2-midifunctions.h. They
- are not an official part of this extension, but they can be convenient.
-*/
-typedef struct {
-
- /** The number of MIDI events in the data buffer.
- INPUT PORTS: It's the host's responsibility to set this field to the
- number of MIDI events contained in the data buffer before calling the
- plugin's run() function. The plugin may not change this field.
- OUTPUT PORTS: It's the plugin's responsibility to set this field to the
- number of MIDI events it has stored in the data buffer before returning
- from the run() function. Any initial value should be ignored by the
- plugin.
- */
- uint32_t event_count;
-
- /** The size of the data buffer in bytes. It is set by the host and may not
- be changed by the plugin. The host is allowed to change this between
- run() calls.
- */
- uint32_t capacity;
-
- /** The size of the initial part of the data buffer that actually contains
- data.
- INPUT PORTS: It's the host's responsibility to set this field to the
- number of bytes used by all MIDI events it has written to the buffer
- (including timestamps and size fields) before calling the plugin's
- run() function. The plugin may not change this field.
- OUTPUT PORTS: It's the plugin's responsibility to set this field to
- the number of bytes used by all MIDI events it has written to the
- buffer (including timestamps and size fields) before returning from
- the run() function. Any initial value should be ignored by the plugin.
- */
- uint32_t size;
-
- /** The data buffer that is used to store MIDI events. The events are packed
- after each other, and the format of each event is as follows:
-
- First there is a timestamp, which should have the type "double",
- i.e. have the same bit size as a double and the same bit layout as a
- double (whatever that is on the current platform). This timestamp gives
- the offset from the beginning of the current cycle, in frames, that
- the MIDI event occurs on. It must be strictly smaller than the 'nframes'
- parameter to the current run() call. The MIDI events in the buffer must
- be ordered by their timestamp, e.g. an event with a timestamp of 123.23
- must be stored after an event with a timestamp of 65.0.
-
- The second part of the event is a size field, which should have the type
- "uint32_t" (as defined in the standard C header stddef.h). It should
- contain the size of the MIDI data for this event, i.e. the number of
- bytes used to store the actual MIDI event. The bytes used by the
- timestamp and the size field should not be counted.
-
- The third part of the event is the actual MIDI data. There are some
- requirements that must be followed:
-
- * Running status is not allowed. Every event must have its own status
- byte.
- * Note On events with velocity 0 are not allowed. These events are
- equivalent to Note Off in standard MIDI streams, but in order to make
- plugins and hosts easier to write, as well as more efficient, only
- proper Note Off events are allowed as Note Off.
- * "Realtime events" (status bytes 0xF8 to 0xFF) are allowed, but may not
- occur inside other events like they are allowed to in hardware MIDI
- streams.
- * All events must be fully contained in a single data buffer, i.e. events
- may not "wrap around" by storing the first few bytes in one buffer and
- then wait for the next run() call to store the rest of the event. If
- there isn't enough space in the current data buffer to store an event,
- the event will either have to wait until next run() call, be ignored,
- or compensated for in some more clever way.
- * All events must be valid MIDI events. This means for example that
- only the first byte in each event (the status byte) may have the eighth
- bit set, that Note On and Note Off events are always 3 bytes long etc.
- The MIDI writer (host or plugin) is responsible for writing valid MIDI
- events to the buffer, and the MIDI reader (plugin or host) can assume
- that all events are valid.
-
- On a platform where double is 8 bytes the data buffer layout for a
- 3-byte event followed by a 4-byte event may look something like this:
- _______________________________________________________________
- | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ...
- |TIMESTAMP 1 |SIZE 1 |DATA |TIMESTAMP 2 |SIZE 2 |DATA | ...
-
- */
- unsigned char* data;
-
-} LV2_MIDI;
-
-
-
-#endif