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Added note about the MPU401 chip.

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git-svn-id: file:///srv/svn/repos/haiku/trunk/current@7575 a95241bf-73f2-0310-859d-f6bbb57e9c96
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mahlzeit
2004-05-14 08:58:36 +00:00
parent 450a95230e
commit c0a1fb7e87
1 changed files with 17 additions and 3 deletions
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docs/develop/midi/stuff.html
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@@ -5,9 +5,23 @@
<UL>
<LI><P>Sometimes the midi_server's debug output shows an "Application -1 not
registered" error message. This means it cannot figure out which app an
incoming BMessage came from. The server ignores those messages.</P>
<LI><P><B>MPU401 kernel module.</B> If your soundcard supports MIDI input and
output, chances are that it is powered by an MPU401 chip. Because this
interface is so popular, BeOS comes with a kernel module that makes it easy to
write drivers for the MPU401. Thanks to Greg Crain, we now have an open source
version of this kernel module.</P>
<P>The mpu401 module lives in <CODE>src/add-ons/kernel/generic/mpu401</CODE>.
It supports both the v1 and (undocumented) v2 protocols, although v2 is not
complete since we don't really know how it works. Unfortunately, almost no
existing drivers use v1; most of the drivers provided by Be require v2.
Currently, the module returns B_ERROR when a MIDI device is opened with
v2.</P></LI>
<LI><P><B>Clients without a BApplication.</B> Sometimes the midi_server's
debug output shows an "Application -1 not registered" error message. This
means it cannot figure out which app an incoming BMessage came from. The
server ignores those messages.</P>
<P>How can this happen? libmidi2 has two ways of sending messages to the
midi_server: it either expects a reply back or not. In the first case, it is