<Sound Dev> Midi Strange behavior on MacOSX.

[Bob Lang]

Hi Guillaume

The problem you describe is most likely due to the Midi Device SPI that Apple ships as part of its Java system.  For a long time Apple didn't ship one at all and there was a thriving market in 3rd party Midi SPIs to fill the gap - and they mostly did a good job because they had to compete to survive.

Unfortunately, when Apple eventually wrote its own SPI, it was nowhere near as good as the 3rd party offerings but it still killed off the market.  I don't think that any 3rd party offerings can be found at all on the web now.

Bob
--
On 10 Dec 2012, at 15:19, guillaume wrote:

> Hello!
> I am writing an application that talks via midi/usb to a guitar effect 
> (Eleven Rack).
> I provide it for free and I have users on Linux, windows and Mac.
> The device sens big sysex messages of more that 1 kb on certain
> circumstances and the behavior on different platform is the following:
> 
> - Linux: receives 1 big sysex message each time.
> - Windows : Receives multpiple sysex messages. The first one is a
> regular sysex (F0...F7) and one or more SPECIAL_SYSEX (F7...F7). I was
> surprised but it seems from reading midi specs that it is the right
> behavior for split sysexes.
> - MacOSX: Receives 1 incomplete sysex (F0...F7) and then nothing... the
> other messages are discarded somwhere...
> 
> I am not a Java expert and I never try to compile Java myself, (this is
> my first java application). But I had a look at the source file
> src/macosx/native/com/sun/media/sound/PLATFORM_API_MacOSX_MidiUtils.c
> and saw that line 375 that Sysexes that starts with F7 are discarded.
> 
> As I understand the specs, some continued messages can start with F7 and
> end with F7. So maybe the solution is to arrange the code this way:
> 
>                        switch (byte) {
>                        case 0xF0:
>                        case 0xF7:
>                            // System exclusive
>                            // Allocates a CFMutableData reference to
> accumulate the SysEx data until EOX (0xF7) is reached.
>                            handle->readingSysExData =
> CFDataCreateMutable(NULL, 0);
>                            break;
> 
> So that messages starting with F7 outside of a sysex message are
> considered as sysex start.
> 
> Is there a way to rebuild only this part of the library to try on a mac?
> I borrowed a mac, installed Java 1.7 (downloaded from oracle) and I have
> the developper tools (clang as a compiler, I think).
> I would like to test the solution.
> Sorry, it may be a naive question, but as a java beginner, the jdk
> sources are really intimidating...
> 
> Yours,
> Guillaume.