Re: [Jack-Devel] Dispersing MIDI messages: one to multiple

Hi Marjan,

On 01/29/2015 11:08 AM, Marjan Mrak wrote:

[..]

> Or is there a better way to "disperse" one MIDI message to several
> channels?

There are existing projects, e.g. midish, mididings, qmidiroute,..
but your hardcoded approach is fine if it addresses your issue.

[..]

> It works, but if I am using it, totaly at random sound output 
> "hangs" for like 10th of second.

As Harry noted, if verb == 1, the printf() debug info could be the
cause (blocking wait for the printed text to reach the terminal).
Other than that there's no obvious reason, but it's a bit hard to read
the code with all the commented out lines all and unscoped variables
over the place.

A few comments below inline:

> static int process(jack_nframes_t nframes, void *arg) { int res =
> 0; int i; int j;
> 
> //unsigned char* buffer; unsigned char jbuffer[3];
> 
> void* port_buf = jack_port_get_buffer(output_port, nframes);
> 
> //get events void* in_port_buf = jack_port_get_buffer(input_port,
> nframes); jack_nframes_t n =
> jack_midi_get_event_count(in_port_buf);
> 
> jack_midi_clear_buffer(port_buf);
> 
> if(n==0) return 0;
> 
> jack_midi_event_t jev;
> 
> 
> if(verb == 1) printf("%i: Data arrived!\n", cnt);
> 
> for(i = 0;i<n;i++){
> 
> res = jack_midi_event_get(&jev,in_port_buf,i); if(res == 0){ 
> if(verb == 1){ printf("Got event, %i bytes!\n",(int) jev.size); 
> for(j=0;j<jev.size;j++) printf("%i: %i\n",j,jev.buffer[j]); } }
> else{ if(verb == 1) printf("ERROR getting event!\n"); return 0; }
> 
> 
> //transmit data cnt++; //buffer = jack_midi_event_reserve(port_buf,
> i, 3);
> 

check the event size

   if (jev.size != 3) {
       continue;
   }

If there are one or two byte messages (eg active-sensing or
midi-clock) at the input, all sorts of undefined behaviour could happen.

Yet, in the code below this should be a non-issue, it always check the
status byte first.

> 
> //controll to MIDI channel 1! if(jev.buffer[0] == 176 &&
> jev.buffer[1] == 97){ if(verb == 1) printf("MUTE CONTROL CH1
> sent\n"); //first button: set mute register on channel 1 
> //buffer[0] = 176; //buffer[1] = 7; //buffer[2] = jev.buffer[2]; 
> jbuffer[0] = 176;

I'd like to suggest to use hex values for the status byte, 0xb0
instead of 176 to improve readability.

> jbuffer[1] = 7; jbuffer[2] = jev.buffer[2]; res =
> jack_midi_event_write(port_buf, jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 96){ if(verb ==
> 1) printf("MUTE CONTROL to CH2 sent\n"); //second button: set mute
> register on channel 2 //buffer[0] = 177; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 177; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 66){ if(verb ==
> 1) printf("MUTE CONTROL CH3 sent\n"); //third button: set mute
> register on channel 3 //buffer[0] = 176; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 178; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 67){ if(verb ==
> 1) printf("MUTE CONTROL to CH4 sent\n"); //fourth button: set mute
> register on channel 4 //buffer[0] = 177; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 179; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 64){ if(verb ==
> 1) printf("MUTE CONTROL to CH5 sent\n"); //fifth button: set mute
> register on channel 5 //buffer[0] = 177; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 180; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 65){ if(verb ==
> 1) printf("MUTE CONTROL to CH6 sent\n"); //sixth button: set mute
> register on channel 6 //buffer[0] = 177; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 181; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 7){ if(verb == 1) 
> printf("MUTE CONTROL to CH7 sent\n"); //seventh button: set mute
> register on channel 7 //buffer[0] = 177; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 182; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> else if(jev.buffer[0] == 176 && jev.buffer[1] == 10){ if(verb ==
> 1) printf("MUTE CONTROL to CH8 sent\n"); //eighth button: set mute
> register on channel 8 //buffer[0] = 177; //buffer[1] = 7; 
> //buffer[2] = jev.buffer[2]; jbuffer[0] = 183; jbuffer[1] = 7; 
> jbuffer[2] = jev.buffer[2]; res = jack_midi_event_write(port_buf,
> jev.time, jbuffer, 3); }
> 
> 
> 
> 
> else if((jev.buffer[0]& 0xF0) == 128 || (jev.buffer[0]& 0xF0) == 
> 144){ //note key, pass through if(verb == 1) printf("SOUND
> PASSED-THROUGH\n"); //notes; let them pass //buffer[0] =
> jev.buffer[0]; //buffer[1] = jev.buffer[1]; //buffer[2] =
> jev.buffer[2]; jbuffer[0] = jev.buffer[0];  //CH1 jbuffer[1] =
> jev.buffer[1]; jbuffer[2] = jev.buffer[2]; res =
> jack_midi_event_write(port_buf, jev.time , jbuffer, 3); jbuffer[0]
> = jev.buffer[0] + 1; //CH2

These can produce invalid messages. e.g some channel 15 data will
alter the status byte. (Note on -> Aftertouch)

uint8_t channel = jev.buffer[0] & 0x0f;
uint8_t status = jev.buffer[0] & 0xf0;
channel = (channel + 1) & 0x0f;
jbuffer[0] = status | channel;


> jbuffer[1] = jev.buffer[1]; jbuffer[2] = jev.buffer[2]; res =
> jack_midi_event_write(port_buf, jev.time , jbuffer, 3); jbuffer[0]
> = jev.buffer[0] + 2; //CH3 jbuffer[1] = jev.buffer[1]; jbuffer[2] =
> jev.buffer[2];

^^ no need to re-assign, jbuffer[1], jbuffer[2]

> res = jack_midi_event_write(port_buf, jev.time , jbuffer, 3); 
> jbuffer[0] = jev.buffer[0] + 3; //CH4 jbuffer[1] = jev.buffer[1]; 
> jbuffer[2] = jev.buffer[2];

ditto.

> res = jack_midi_event_write(port_buf, jev.time , jbuffer, 3); }
> 
> //res = jack_midi_event_write(port_buf, i, jev.buffer, 3); //res =
> jack_midi_event_write(port_buf, jev.time, jbuffer, 3);
> 

Just stop if you can't write more events or a write failed.

    if (!res) {
        break;
    }

but that's just some minor optimization. It won't hurt much to keep
calling jack_midi_event_write() again. it will just be a no-op. It's
very unlikely to happen anyway.

> 
> }
> 
> return 0;
> 
> }

It should work in principle, maybe there's a flaw elsewhere in the
setup code.

Cheers!
robin

1422541181.25254_0.ltw:2, <54CA416F.9070905 at gareus dot org>