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Diffstat (limited to 'src')
| -rw-r--r-- | src/common/lv2ext/lv2-midiport.h | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/src/common/lv2ext/lv2-midiport.h b/src/common/lv2ext/lv2-midiport.h new file mode 100644 index 00000000..63980f64 --- /dev/null +++ b/src/common/lv2ext/lv2-midiport.h @@ -0,0 +1,179 @@ +/**************************************************************************** + + 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 |