audio.jack.autoconnect erroneously connects to MIDI ports

[ReinholdH]

When using audio.jack.multi=1 not all ports and fx are connected, and as a consequence - after the bug happens - ports are connected alternating to the wrong output side. The bug is in fluid_jack.c line 637, 658

If jack_connect fails with err because jack_ports[o] won't exist "i" needs to be decremented. See "i--" added in order to connect port "i" to jack_ports[0] again. Otherwise port "i" does not get connected, and the following port gets connected to the wrong output side.

Here is the snapshot of fluid_jack.c starting with line 613
` if(autoconnect)
{
jack_ports = jack_get_ports(client, NULL, NULL, JackPortIsInput | JackPortIsPhysical);

    if(jack_ports && jack_ports[0])
    {
        int err, o = 0;
        int connected = 0;

        for(i = 0; i < 2 * dev->num_output_ports; ++i)
        {
            err = jack_connect(client, jack_port_name(dev->output_ports[i]), jack_ports[o++]);

            if(err)
            {
                FLUID_LOG(FLUID_ERR, "Error connecting jack port");
            }
            else
            {
                connected++;
            }

           if (!jack_ports[o])
           {
                o = 0;
                i--;    //  i needs to be decremented
            }
        }

        o = 0;
        for(i = 0; i < 2 * dev->num_fx_ports; ++i)
        {
            err = jack_connect(client, jack_port_name(dev->fx_ports[i]), jack_ports[o++]);

            if(err)
            {
                FLUID_LOG(FLUID_ERR, "Error connecting jack port");
            }
            else
            {
                connected++;
            }

            if (!jack_ports[o])
            {
                o = 0;
                i--; //  i needs to be decremented
            }
        }

        jack_free(jack_ports);   /* free jack ports array (not the port values!) */
    }
    else
    {
        FLUID_LOG(FLUID_WARN, "Could not connect to any physical jack ports; fluidsynth is unconnected");
    }
}`

I hope this is the final solution. Works fine in my setup. Can somebody double-check. Thx.

[ReinholdH]

I want to add that the used settings are

audio.jack.multi=1
synth.audio-channels=16
synth.audio-groups=16

[derselbst]

The purpose of that line

fluidsynth/src/drivers/fluid_jack.c

Line 635 in 97eefe9

if(!jack_ports[o])

is to check whether we have reached the end of the NULL terminated array of Jack's physical ports. Note that o has been incremented during the jack_connect call, so this now points to the next port. This is not related to any potential connection error during jack_connect.

With your change, some of fluidsynth's ports are being connected twice (e.g. l05, l10, l15, r02, r07, r12):

You probably meant to decrement i in that if-clause:

fluidsynth/src/drivers/fluid_jack.c

Lines 626 to 629 in 97eefe9

	if(err)
	{
	FLUID_LOG(FLUID_ERR, "Error connecting jack port");
	}

However, doing so is potentially dangerous as it might cause the loop to never terminate.

I think it would be better to figure out why jack is failing to connect to these ports. Any details that caused the error?

[ReinholdH]

Thanks for the immediate response. Yes, I agree. My proposal from above is wrong but the solution is much more simple.

"audio autoconnect" needs to be restricted to audio ports only :-).

In line 615 of fluid_jack.cpp
jack_ports = jack_get_ports(client, NULL, NULL, JackPortIsInput | JackPortIsPhysical);
all ports are taken into account including MIDI ports. If MIDI ports are present and activated in addition to audio ports the "audio autoconnect" fails. Line 615 needs to be
jack_ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput | JackPortIsPhysical);
This change works fine in my setup. Is this proposal OK?

[derselbst]

Oh, ofc. Thanks Reinhold! Just opened the PR.