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ALSA: Work around a firmware bug in USB-MIDI cables.

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Thanks to waltervn (and wjp) for their investigation on this and Walter's SCI
specific workaround which I more or less just copied here so it will apply for
all engines.
This commit is contained in:
Johannes Schickel 2011-03-10 04:40:30 +01:00
parent 40e9374679
commit 601a09e417
1 changed files with 21 additions and 1 deletions
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22
backends/midi/alsa.cpp
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@ -83,10 +83,12 @@ private:
snd_seq_t *seq_handle;
int seq_client, seq_port;
int my_client, my_port;
// The volume controller value of the first MIDI channel
int8 _channel0Volume;
};
MidiDriver_ALSA::MidiDriver_ALSA(int client, int port)
: _isOpen(false), seq_handle(0), seq_client(client), seq_port(port), my_client(0), my_port(0)
: _isOpen(false), seq_handle(0), seq_client(client), seq_port(port), my_client(0), my_port(0), _channel0Volume(127)
{
memset(&ev, 0, sizeof(ev));
}
@ -208,15 +210,33 @@ void MidiDriver_ALSA::send(uint32 b) {
case 0xB0:
/* is it this simple ? Wow... */
snd_seq_ev_set_controller(&ev, chanID, midiCmd[1], midiCmd[2]);
// We save the volume of the first MIDI channel here to utilize it in
// our workaround for broken USB-MIDI cables.
if (chanID == 0 && midiCmd[1] == 0x07)
_channel0Volume = midiCmd[2];
send_event(1);
break;
case 0xC0:
snd_seq_ev_set_pgmchange(&ev, chanID, midiCmd[1]);
send_event(0);
// Send a volume change command to work around a firmware bug in common
// USB-MIDI cables. If the first MIDI command in a USB packet is a
// Cx or Dx command, the second command in the packet is dropped
// somewhere.
send(0x07B0 | (_channel0Volume << 16));
break;
case 0xD0:
snd_seq_ev_set_chanpress(&ev, chanID, midiCmd[1]);
send_event(1);
// Send a volume change command to work around a firmware bug in common
// USB-MIDI cables. If the first MIDI command in a USB packet is a
// Cx or Dx command, the second command in the packet is dropped
// somewhere.
send(0x07B0 | (_channel0Volume << 16));
break;
case 0xE0:{
// long theBend = ((((long)midiCmd[1] + (long)(midiCmd[2] << 7))) - 0x2000) / 4;