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1995-09-11
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6. _M_I_D_I
The MIDI execution environment consists of the kernel MIDI
driver, the MIDI library DSO _l_i_b_m_d._s_o, and the _s_t_a_r_t_m_i_d_i(1)
and _s_t_o_p_m_i_d_i(1) commands.
The MIDI driver allows applications programs to read or send
time-stamped MIDI events via one or both of the serial ports
on an Indy, Indigo, Indigo, or 4D/35 workstation. The MIDI
library provides an application programming interface to the
capabilities of the driver.
In order to operate a serial port on your IRIS workstation
as a MIDI port, you must first connect it to a standard
Apple Macintosh-compatible serial-to-MIDI interface. Many of
these interfaces offer additional useful features, such as
SMPTE time-code conversion.
Before any MIDI applications can be run, it is usually
necessary to configure the serial ports for use with MIDI.
This is done through the System Manager Port Tool. Bring up
the Port Tool, and connect the desired serial port to a MIDI
device. To use the port for other devices (such as a
printer), simply disconnect the port using the Port Tool,
and then connect to whatever device you desire. The name of
the MIDI port will be "midiPortX", where X is either 1 or 2,
depending upon which serial port you connect to.
6.1 _K_n_o_w_n__P_r_o_b_l_e_m_s__a_n_d__W_o_r_k_a_r_o_u_n_d_s
+o There is a known driver problem related to operating
MIDI ports through serial port 1 on an Indigo, Indigo2,
or Indy system. MIDI applications which open
connections on serial port 1 may cause kernel panics.
This problem will not show up immediately when the
application is invoked. It occurs sporadically. If you
do have problems connecting to port 1, please contact
the TAC (800.800.4SGI).
Problem: MIDI crash due to 'getty' running on
/dev/ttyd1.
Workaround: modify /etc/inittab
Change "respawn" to "off" in the following line:
# on-board ports or on Challenge/Onyx MP machines,
first IO4 board ports
t1:23:respawn:/sbin/getty ttyd1 co_9600 #alt console
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Then run 'telinit':
# telinit q
Otherwise: Connect external MIDI adapters to serial
port 2 only.
+o Machines have been observed to crash as a consequence
of changing the physical location of cables while MIDI
is running.
It is recommended that changes to the cabling of MIDI
only be done while the machine is powered down.
+o Currently, the MIDI system does not automatically
synchronize to an external sequencer or drum machine,
nor does it generate MIDI clocks to synchronize other
devices.
+o Some Indigo^2 machines exhibit erratic behavior when
receiving system exclusive messages. If you have a
problem, please contact the TAC (800.800.4SGI).
6.2 _C_h_a_n_g_e_s__a_n_d__A_d_d_i_t_i_o_n_s
This section lists changes and additions since the 5.2
release.
+o MIDI can now be started and stopped on ports
individually. That is, you can now start and stop MIDI
on one port without affecting it on another.
+o MIDI configuration of the serial ports can now be done
with the Port Setup tool in the System Manager. If you
do not use the System Manager, you may still use MIDI,
but it is necessary to manage the access to the serial
port manually, making sure that no other process is
attempting to use the serial port while it is
configured for MIDI. Pay particular attention to the
entries for the serial ports /etc/inittab.
+o IRIS Digital Media Development Environment 5.3
(included with the standard IRIS Development Option
5.3) provides 4Dgifts source code for a number of new
MIDI utilities including command-line and graphical
Standard MIDI File player programs.