On 03/05/2013 02:56 AM, Joerg-Cyril.Hoehle@t-systems.com wrote:
Now, consider an app playing a MIDI file or a debug tool that allows to send arbitrary messages. How should such an app send e.g. the 2-byte MTC Quarter Frame sequence via ALSA?
If you want to send arbitrary MIDI messages, you'll find the rawmidi interface more flexible. The seq interface is very restrictive in this case.
For example, I think you can send arbitrary (even random/invalid) stuff using the CLI `amidi`. It was intended for Sysex dumps, but I think it's more flexable. It uses the rawmidi api.
http://www.alsa-project.org/alsa-doc/alsa-lib/group___raw_midi.html
The down-side of using rawmidi is that you're now on your own for sequencing (timing).
A. Use a 2 byte buffer F1 xx and snd_seq_ev_set_sysex(&event, 2, buf);
Set up a snd_seq_event_t with type SND_SEQ_EVENT_QFRAME and fill out the snd_seq_event_t::control structure with the appropriate data. Your 1-byte payload message should go into the 'value' field... and ignore the 'channel' and 'param' fields.
B. Use SND_SEQ_EVENT_TICK and figure out some copy&paste code from seqmidi.h, perhaps snd_seq_ev_set_queue_control(ev,SND_SEQ_EVENT_TICK,SND_SEQ_QUEUE_DIRECT,xx) But why does that alter my destination port via snd_seq_ev_set_dest(ev, SND_SEQ_CLIENT_SYSTEM, SND_SEQ_PORT_SYSTEM_TIMER)?
Inspecting the source, it looks like the kernel seq driver drops the non-standard 'Tick' message (0xF9). The only way I know to send it is to use the rawmidi API. [Anybody: please correct me if I'm wrong here.]
Background: Wine on Linux needs to generate such messages on behalf of applications and users with real MIDI HW. So far Wine assumes that it can encapsulate all system messages in a SysEx, IOW Wine does A. Is that usage of the set_sysex API correct? More generally, can Wine transparently stuff system messages into a byte buffer and send them off via snd_seq_ev_set_sysex?
Since Wine is sending/receiving midi data (without timing) that is to be sent/received _immediately_ -- you might find life easier by using the rawmidi api. Using this, it might even be as simple as passing raw data back and forth without having to decode anything yourself.
-gabriel