Portmidi does not lock anything, but it does call the underlying system
API to open the device. I just ran a quick test on OS X and Vista, and
both allowed me to open the same output device from two applications. OS
X allows multiple applications to open the same input device, and copies
of the input go to each application. I didn't have input conveniently
set up on Vista, and I'm not sure what ALSA does. I think WinXP did not
allow midi output devices to be opened multiple times.
-Roger
On 2/16/11 10:03 AM, Tim Burgess wrote:
Hi,
Thanks for the clarification. Does that lock apply, even with
multi-client hardware drivers?
Best wishes.
Tim Burgess
Raised Bar Ltd
Phone: +44 (0)1827 719822
Don't forget to vote for improved access to music and music technology at
http://www.raisedbar.net/petition.htm
*From:*Roger Dannenberg [mailto:[email protected]]
*Sent:* 16 February 2011 14:15
*To:* [email protected]
*Cc:* [email protected]
*Subject:* Re: [Media_api] PortMIDI Device enumeration
Yes, device ID values are 0-based. You should not assume any
particular ordering, so if you want to separate the input and output
devices, you should test each device for input or output and add it to
the appropriate list.
The PmDefaults program does this. It is written in Java, but the code
that populates the drop-down boxes should be easy to follow, and you
might be interested to see the "test" button it provides where the
user can verify correct output device selection, and a "test" light to
show when input arrives on the selected input device.
I'll also mention that if you open devices for testing or anything
else, you may end up with an exclusive lock on the device that
prevents other applications from opening the device until the original
program closes the device.
-Roger
On 2/16/11 7:40 AM, Tim Burgess wrote:
Hi,
I'm just checking my understanding of how PortMIDI enumerates the
available I/O ports. I understand that device ID values are 0-based
and that I can check whether a given port is an input or output
device, but can I always assume that input ports are listed first,
followed by output ports? I'm populating a couple of list boxes in a
Windows application so that the user can choose which ports they want
to use, so I need to convert the relevant list box index into a valid
device ID to bind to a PmStream.
Best wishes.
Tim Burgess
Raised Bar Ltd
Phone: +44 (0)1827 719822
Don't forget to vote for improved access to music and music technology at
http://www.raisedbar.net/petition.htm
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