Hi smart pd-dev people, please help me. I'm miserably failing in designing new externals with the amazing new multi-channel feature.

Getting inspired by some of the MAX objects, for fun and for starters I thought I'd clonen [mc.list~], which is kinda like the new [pack~] but you can set the values as arguments. It would also allow us to use the list box to set all values.

My first and only 'mc' external so far is [nchs~], see --> https://github.com/porres/pd-else/blob/master/Classes/Source/nchs~.c I already mentioned it and said it'd be cool to have it in Vanilla. It outputs a float value but I wanted, as a first step, to adapt it to output a signal value instead, but I can't do not even that, let alone have a new external that outputs a multichannel signal. From the [nchs~] code, I just use the 'dsp method' to get 'sp[0]->s_nchans' (number of channels) and call a bang function that outputs the float.

If I create a 'perform' method to get number of channels as a signal, Pd blows up, and I don't know what I'm doing wrong as I'm doing what I do with every other regular external. Not that I wanted a signal output, I'd rather have the float output, but I expected this to work and I can't see the problem. I am assuming multichannel externals are different and I don't really know the secret or the recipe yet to mess with them. Check code below.

static t_int *nchs_perform(t_int *w){

    t_check *x = (t_check *)(w[1]);

    int n = (t_int)(w[2]);

    t_sample *in = (t_sample *)(w[3]);

    t_sample *out = (t_sample *)(w[4]);

    while(n--)

        *out = x->x_nchans;

    return(w+5);

}


static void nchs_tilde_dsp(t_check *x, t_signal **sp){

    x->x_nchans = sp[0]->s_nchans;

    dsp_add(check_perform, 4, x, sp[0]->s_n, sp[0]->s_vec, sp[1]->s_vec);

} 

I can't imagine the further challenges to output or treat multichannel signals, but I'd like to start by clarifying this.

funny enough, [pack~]/[unpack~] do not have 'perform' methods so I can't figure this out.

Thanks a lot.
cheers~