I tested this here on OSX and got:

instr 1:  iPol = 64.000
  rtevent:	   T  2.160 TT  2.160 M:      0.0
  rtevent:	   T  2.252 TT  2.252 M:      0.0


So the behavior is certainly odd.  I did some looking into it and it
looks like what is happening is that midi-key is writing into p4.
However, because this instrument does not have a p4 defined within the
instrument body, the instrument is allocating only 3 pfields.  When
insert.c reads and finds midi-key is set, it just goes to write into
memory 3 spots after p1, which is essentially undefined memory.  In
this case, it's happening to be the address where a channel "kC14" was
allocated at.

I was able to get around it by using a dummy value for p4:

instr   1
ival = p4
kPolarity       chnget  "kC14"
iPol            =       i(kPolarity)
                print   iPol            ;print the midinote number !!!
endin

That will work as a workaround.  We could perhaps check pmax and if
the midi-key is greater than pmax, don't attempt to set a value.
However, I don't know if this will help if there are n-number of
p-args.  This seems to be a scenario which goes beyond Csound's
original design, as pmax is set when parsing the orchestra and looking
at the code. I suspect it will take some time to understand the
ramifications of changing this (perhaps other developers will take a
look, I won't have time to look at this further any time soon,
unfortunately).

Thanks,
steven



On Thu, Feb 23, 2012 at 3:54 PM, Rene Jopi  wrote:
> Hi list,
>
> I found why some of my RT midi csd are broken.
>
> I use Csound 5.16.1 compiled on Ubuntu 10.04.
>
> In the following example the printed value of iPol is equal to the played
> note number !!
> It should be zero.
>
> The problem arise if I use --midi-key, chnget and i() opcode.
>
> 
> 
> -d -odac -+rtaudio=alsa -+rtmidi=alsa -Ma --midi-key=4
> 
> 
>
> chn_k "kC14", 1
>
> instr 1
> kPolarity chnget "kC14"
> iPol = i(kPolarity)
> print iPol ;print the midi note number !!!
> endin
> 
> 
> f 0 3600
> 
> 
>
>
> To add my feeling to the previous thread (Time line in blue......),
> I say a big THANK YOU to all the peoples involved in these fantastic
> projects like Csound, Blue, CsoundQt, my everyday tools to enjoy :)
>
> Best regards
> René
>