410 lines
15 KiB
HTML
410 lines
15 KiB
HTML
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
||
|
|
<HTML>
|
||
|
|
<HEAD>
|
||
|
|
<TITLE>OSS Sequencer Emulation on ALSA</TITLE>
|
||
|
|
</HEAD>
|
||
|
|
<BODY>
|
||
|
|
|
||
|
|
<CENTER>
|
||
|
|
<H1>
|
||
|
|
|
||
|
|
<HR WIDTH="100%"></H1></CENTER>
|
||
|
|
|
||
|
|
<CENTER>
|
||
|
|
<H1>
|
||
|
|
OSS Sequencer Emulation on ALSA</H1></CENTER>
|
||
|
|
|
||
|
|
<HR WIDTH="100%">
|
||
|
|
<P>Copyright (c) 1998,1999 by Takashi Iwai
|
||
|
|
<TT><A HREF="mailto:iwai@ww.uni-erlangen.de"><iwai@ww.uni-erlangen.de></A></TT>
|
||
|
|
<P>ver.0.1.8; Nov. 16, 1999
|
||
|
|
<H2>
|
||
|
|
|
||
|
|
<HR WIDTH="100%"></H2>
|
||
|
|
|
||
|
|
<H2>
|
||
|
|
1. Description</H2>
|
||
|
|
This directory contains the OSS sequencer emulation driver on ALSA. Note
|
||
|
|
that this program is still in the development state.
|
||
|
|
<P>What this does - it provides the emulation of the OSS sequencer, access
|
||
|
|
via
|
||
|
|
<TT>/dev/sequencer</TT> and <TT>/dev/music</TT> devices.
|
||
|
|
The most of applications using OSS can run if the appropriate ALSA
|
||
|
|
sequencer is prepared.
|
||
|
|
<P>The following features are emulated by this driver:
|
||
|
|
<UL>
|
||
|
|
<LI>
|
||
|
|
Normal sequencer and MIDI events:</LI>
|
||
|
|
|
||
|
|
<BR>They are converted to the ALSA sequencer events, and sent to the corresponding
|
||
|
|
port.
|
||
|
|
<LI>
|
||
|
|
Timer events:</LI>
|
||
|
|
|
||
|
|
<BR>The timer is not selectable by ioctl. The control rate is fixed to
|
||
|
|
100 regardless of HZ. That is, even on Alpha system, a tick is always
|
||
|
|
1/100 second. The base rate and tempo can be changed in <TT>/dev/music</TT>.
|
||
|
|
|
||
|
|
<LI>
|
||
|
|
Patch loading:</LI>
|
||
|
|
|
||
|
|
<BR>It purely depends on the synth drivers whether it's supported since
|
||
|
|
the patch loading is realized by callback to the synth driver.
|
||
|
|
<LI>
|
||
|
|
I/O controls:</LI>
|
||
|
|
|
||
|
|
<BR>Most of controls are accepted. Some controls
|
||
|
|
are dependent on the synth driver, as well as even on original OSS.</UL>
|
||
|
|
Furthermore, you can find the following advanced features:
|
||
|
|
<UL>
|
||
|
|
<LI>
|
||
|
|
Better queue mechanism:</LI>
|
||
|
|
|
||
|
|
<BR>The events are queued before processing them.
|
||
|
|
<LI>
|
||
|
|
Multiple applications:</LI>
|
||
|
|
|
||
|
|
<BR>You can run two or more applications simultaneously (even for OSS sequencer)!
|
||
|
|
However, each MIDI device is exclusive - that is, if a MIDI device is opened
|
||
|
|
once by some application, other applications can't use it. No such a restriction
|
||
|
|
in synth devices.
|
||
|
|
<LI>
|
||
|
|
Real-time event processing:</LI>
|
||
|
|
|
||
|
|
<BR>The events can be processed in real time without using out of bound
|
||
|
|
ioctl. To switch to real-time mode, send ABSTIME 0 event. The followed
|
||
|
|
events will be processed in real-time without queued. To switch off the
|
||
|
|
real-time mode, send RELTIME 0 event.
|
||
|
|
<LI>
|
||
|
|
<TT>/proc</TT> interface:</LI>
|
||
|
|
|
||
|
|
<BR>The status of applications and devices can be shown via <TT>/proc/asound/seq/oss</TT>
|
||
|
|
at any time. In the later version, configuration will be changed via <TT>/proc</TT>
|
||
|
|
interface, too.</UL>
|
||
|
|
|
||
|
|
<H2>
|
||
|
|
2. Installation</H2>
|
||
|
|
Run configure script with both sequencer support (<TT>--with-sequencer=yes</TT>)
|
||
|
|
and OSS emulation (<TT>--with-oss=yes</TT>) options. A module <TT>snd-seq-oss.o</TT>
|
||
|
|
will be created. If the synth module of your sound card supports for OSS
|
||
|
|
emulation (so far, only Emu8000 driver), this module will be loaded automatically.
|
||
|
|
Otherwise, you need to load this module manually.
|
||
|
|
<P>At beginning, this module probes all the MIDI ports which have been
|
||
|
|
already connected to the sequencer. Once after that, the creation and deletion
|
||
|
|
of ports are watched by announcement mechanism of ALSA sequencer.
|
||
|
|
<P>The available synth and MIDI devices can be found in proc interface.
|
||
|
|
Run "<TT>cat /proc/asound/seq/oss</TT>", and check the devices. For example,
|
||
|
|
if you use an AWE64 card, you'll see like the following:
|
||
|
|
<PRE> OSS sequencer emulation version 0.1.8
|
||
|
|
ALSA client number 63
|
||
|
|
ALSA receiver port 0
|
||
|
|
|
||
|
|
Number of applications: 0
|
||
|
|
|
||
|
|
Number of synth devices: 1
|
||
|
|
|
||
|
|
synth 0: [EMU8000]
|
||
|
|
type 0x1 : subtype 0x20 : voices 32
|
||
|
|
capabilties : ioctl enabled / load_patch enabled
|
||
|
|
|
||
|
|
Number of MIDI devices: 3
|
||
|
|
|
||
|
|
midi 0: [Emu8000 Port-0] ALSA port 65:0
|
||
|
|
capability write / opened none
|
||
|
|
|
||
|
|
midi 1: [Emu8000 Port-1] ALSA port 65:1
|
||
|
|
capability write / opened none
|
||
|
|
|
||
|
|
midi 2: [0: MPU-401 (UART)] ALSA port 64:0
|
||
|
|
capability read/write / opened none</PRE>
|
||
|
|
Note that the device number may be different from the information of
|
||
|
|
<TT>/proc/asound/oss-devices</TT>
|
||
|
|
or ones of the original OSS driver. Use the device number listed in <TT>/proc/asound/seq/oss</TT>
|
||
|
|
to play via OSS sequencer emulation.
|
||
|
|
<H2>
|
||
|
|
3. Using Synthesizer Devices</H2>
|
||
|
|
Run your favorite program. I've tested playmidi-2.4, awemidi-0.4.3, gmod-3.1
|
||
|
|
and xmp-1.1.5. You can load samples via <TT>/dev/sequencer</TT> like sfxload,
|
||
|
|
too.
|
||
|
|
<P>If the lowlevel driver supports multiple access to synth devices (like
|
||
|
|
Emu8000 driver), two or more applications are allowed to run at the same
|
||
|
|
time.
|
||
|
|
<H2>
|
||
|
|
4. Using MIDI Devices</H2>
|
||
|
|
So far, only MIDI output was tested. MIDI input was not checked at all,
|
||
|
|
but hopefully it will work. Use the device number listed in <TT>/proc/asound/seq/oss</TT>.
|
||
|
|
Be aware that these numbers are mostly different from the list in
|
||
|
|
<TT>/proc/asound/oss-devices</TT>.
|
||
|
|
<H2>
|
||
|
|
5. Module Options</H2>
|
||
|
|
The following module options are available:
|
||
|
|
<UL>
|
||
|
|
<LI>
|
||
|
|
<TT>maxqlen</TT></LI>
|
||
|
|
|
||
|
|
<BR>specifies the maximum read/write queue length. This queue is private
|
||
|
|
for OSS sequencer, so that it is independent from the queue length of ALSA
|
||
|
|
sequencer. Default value is 1024.
|
||
|
|
<LI>
|
||
|
|
<TT>seq_oss_debug</TT></LI>
|
||
|
|
|
||
|
|
<BR>specifies the debug level and accepts zero (= no debug message) or
|
||
|
|
positive integer. Default value is 0.</UL>
|
||
|
|
|
||
|
|
<H2>
|
||
|
|
6. Queue Mechanism</H2>
|
||
|
|
OSS sequencer emulation uses an ALSA priority queue. The
|
||
|
|
events from <TT>/dev/sequencer</TT> are processed and put onto the queue
|
||
|
|
specified by module option.
|
||
|
|
<P>All the events from <TT>/dev/sequencer</TT> are parsed at beginning.
|
||
|
|
The timing events are also parsed at this moment, so that the events may
|
||
|
|
be processed in real-time. Sending an event ABSTIME 0 switches the operation
|
||
|
|
mode to real-time mode, and sending an event RELTIME 0 switches it off.
|
||
|
|
In the real-time mode, all events are dispatched immediately.
|
||
|
|
<P>The queued events are dispatched to the corresponding ALSA sequencer
|
||
|
|
ports after scheduled time by ALSA sequencer dispatcher.
|
||
|
|
<P>If the write-queue is full, the application sleeps until a certain amount
|
||
|
|
(as default one half) becomes empty in blocking mode. The synchronization
|
||
|
|
to write timing was implemented, too.
|
||
|
|
<P>The input from MIDI devices or echo-back events are stored on read FIFO
|
||
|
|
queue. If application reads <TT>/dev/sequencer</TT> in blocking mode, the
|
||
|
|
process will be awaked.
|
||
|
|
|
||
|
|
<H2>
|
||
|
|
7. Interface to Synthesizer Device</H2>
|
||
|
|
|
||
|
|
<H3>
|
||
|
|
7.1. Registration</H3>
|
||
|
|
To register an OSS synthesizer device, use <TT>snd_seq_oss_synth_register</TT>
|
||
|
|
function.
|
||
|
|
<PRE>int snd_seq_oss_synth_register(char *name, int type, int subtype, int nvoices,
|
||
|
|
snd_seq_oss_callback_t *oper, void *private_data)</PRE>
|
||
|
|
The arguments <TT>name</TT>, <TT>type</TT>, <TT>subtype</TT> and
|
||
|
|
<TT>nvoices</TT>
|
||
|
|
are used for making the appropriate synth_info structure for ioctl. The
|
||
|
|
return value is an index number of this device. This index must be remembered
|
||
|
|
for unregister. If registration is failed, -errno will be returned.
|
||
|
|
<P>To release this device, call <TT>snd_seq_oss_synth_unregister function</TT>:
|
||
|
|
<PRE>int snd_seq_oss_synth_unregister(int index),</PRE>
|
||
|
|
where the <TT>index</TT> is the index number returned by register function.
|
||
|
|
<H3>
|
||
|
|
7.2. Callbacks</H3>
|
||
|
|
OSS synthesizer devices have capability for sample downloading and ioctls
|
||
|
|
like sample reset. In OSS emulation, these special features are realized
|
||
|
|
by using callbacks. The registration argument oper is used to specify these
|
||
|
|
callbacks. The following callback functions must be defined:
|
||
|
|
<PRE>snd_seq_oss_callback_t:
|
||
|
|
int (*open)(snd_seq_oss_arg_t *p, void *closure);
|
||
|
|
int (*close)(snd_seq_oss_arg_t *p);
|
||
|
|
int (*ioctl)(snd_seq_oss_arg_t *p, unsigned int cmd, unsigned long arg);
|
||
|
|
int (*load_patch)(snd_seq_oss_arg_t *p, int format, const char *buf, int offs, int count);
|
||
|
|
int (*reset)(snd_seq_oss_arg_t *p);
|
||
|
|
Except for <TT>open</TT> and <TT>close</TT> callbacks, they are allowed
|
||
|
|
to be NULL.
|
||
|
|
<P>Each callback function takes the argument type snd_seq_oss_arg_t as the
|
||
|
|
first argument.
|
||
|
|
<PRE>struct snd_seq_oss_arg_t {
|
||
|
|
int app_index;
|
||
|
|
int file_mode;
|
||
|
|
int seq_mode;
|
||
|
|
snd_seq_addr_t addr;
|
||
|
|
void *private_data;
|
||
|
|
int event_passing;
|
||
|
|
};</PRE>
|
||
|
|
The first three fields, <TT>app_index</TT>, <TT>file_mode</TT> and
|
||
|
|
<TT>seq_mode</TT>
|
||
|
|
are initialized by OSS sequencer. The <TT>app_index</TT> is the application
|
||
|
|
index which is unique to each application opening OSS sequencer. The
|
||
|
|
<TT>file_mode</TT>
|
||
|
|
is bit-flags indicating the file operation mode. See
|
||
|
|
<TT>seq_oss.h</TT>
|
||
|
|
for its meaning. The <TT>seq_mode</TT> is sequencer operation mode. In
|
||
|
|
the current version, only <TT>SND_OSSSEQ_MODE_SYNTH</TT> is used.
|
||
|
|
<P>The next two fields, <TT>addr</TT> and <TT>private_data</TT>, must be
|
||
|
|
filled by the synth driver at open callback. The <TT>addr</TT> contains
|
||
|
|
the address of ALSA sequencer port which is assigned to this device. If
|
||
|
|
the driver allocates memory for <TT>private_data</TT>, it must be released
|
||
|
|
in close callback by itself.
|
||
|
|
<P>The last field, <TT>event_passing</TT>, indicates how to translate note-on
|
||
|
|
/ off events. In <TT>PROCESS_EVENTS</TT> mode, the note 255 is regarded
|
||
|
|
as velocity change, and key pressure event is passed to the port. In <TT>PASS_EVENTS</TT>
|
||
|
|
mode, all note on/off events are passed to the port without modified. <TT>PROCESS_KEYPRESS</TT>
|
||
|
|
mode checks the note above 128 and regards it as key pressure event (mainly
|
||
|
|
for Emu8000 driver).
|
||
|
|
<H4>
|
||
|
|
7.2.1. Open Callback</H4>
|
||
|
|
The <TT>open</TT> is called at each time this device is opened by an application
|
||
|
|
using OSS sequencer. This must not be NULL. Typically, the open callback
|
||
|
|
does the following procedure:
|
||
|
|
<OL>
|
||
|
|
<LI>
|
||
|
|
Allocate private data record.</LI>
|
||
|
|
|
||
|
|
<LI>
|
||
|
|
Create an ALSA sequencer port.</LI>
|
||
|
|
|
||
|
|
<LI>
|
||
|
|
Set the new port address on arg->addr.</LI>
|
||
|
|
|
||
|
|
<LI>
|
||
|
|
Set the private data record pointer on arg->private_data.</LI>
|
||
|
|
</OL>
|
||
|
|
Note that the type bit-flags in port_info of this synth port must NOT contain
|
||
|
|
<TT>TYPE_MIDI_GENERIC</TT>
|
||
|
|
bit. Instead, <TT>TYPE_SPECIFIC</TT> should be used. Also, <TT>CAP_SUBSCRIPTION</TT>
|
||
|
|
bit should NOT be included, too. This is necessary to tell it from other
|
||
|
|
normal MIDI devices. If the open procedure succeeded, return zero. Otherwise,
|
||
|
|
return -errno.
|
||
|
|
<H4>
|
||
|
|
7.2.2 Ioctl Callback</H4>
|
||
|
|
The <TT>ioctl</TT> callback is called when the sequencer receives device-specific
|
||
|
|
ioctls. The following two ioctls should be processed by this callback:
|
||
|
|
<UL>
|
||
|
|
<LI>
|
||
|
|
<TT>IOCTL_SEQ_RESET_SAMPLES</TT></LI>
|
||
|
|
|
||
|
|
<BR>reset all samples on memory -- return 0
|
||
|
|
<LI>
|
||
|
|
<TT>IOCTL_SYNTH_MEMAVL</TT></LI>
|
||
|
|
|
||
|
|
<BR>return the available memory size
|
||
|
|
<LI>
|
||
|
|
<TT>FM_4OP_ENABLE</TT></LI>
|
||
|
|
|
||
|
|
<BR>can be ignored usually</UL>
|
||
|
|
The other ioctls are processed inside the sequencer without passing to
|
||
|
|
the lowlevel driver.
|
||
|
|
<H4>
|
||
|
|
7.2.3 Load_Patch Callback</H4>
|
||
|
|
The <TT>load_patch</TT> callback is used for sample-downloading. This callback
|
||
|
|
must read the data on user-space and transfer to each device. Return 0
|
||
|
|
if succeeded, and -errno if failed. The format argument is the patch key
|
||
|
|
in patch_info record. The buf is user-space pointer where patch_info record
|
||
|
|
is stored. The offs can be ignored. The count is total data size of this
|
||
|
|
sample data.
|
||
|
|
<H4>
|
||
|
|
7.2.4 Close Callback</H4>
|
||
|
|
The <TT>close</TT> callback is called when this device is closed by the
|
||
|
|
applicaion. If any private data was allocated in open callback, it must
|
||
|
|
be released in the close callback. The deletion of ALSA port should be
|
||
|
|
done here, too. This callback must not be NULL.
|
||
|
|
<H4>
|
||
|
|
7.2.5 Reset Callback</H4>
|
||
|
|
The <TT>reset</TT> callback is called when sequencer device is reset or
|
||
|
|
closed by applications. The callback should turn off the sounds on the
|
||
|
|
relevant port immediately, and initialize the status of the port. If this
|
||
|
|
callback is undefined, OSS seq sends a <TT>HEARTBEAT</TT> event to the
|
||
|
|
port.
|
||
|
|
<H3>
|
||
|
|
7.3 Events</H3>
|
||
|
|
Most of the events are processed by sequencer and translated to the adequate
|
||
|
|
ALSA sequencer events, so that each synth device can receive by input_event
|
||
|
|
callback of ALSA sequencer port. The following ALSA events should be implemented
|
||
|
|
by the driver:
|
||
|
|
<BR>
|
||
|
|
<TABLE BORDER WIDTH="75%" NOSAVE >
|
||
|
|
<TR NOSAVE>
|
||
|
|
<TD NOSAVE><B>ALSA event</B></TD>
|
||
|
|
|
||
|
|
<TD><B>Original OSS events</B></TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>NOTEON</TD>
|
||
|
|
|
||
|
|
<TD>SEQ_NOTEON
|
||
|
|
<BR>MIDI_NOTEON</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>NOTE</TD>
|
||
|
|
|
||
|
|
<TD>SEQ_NOTEOFF
|
||
|
|
<BR>MIDI_NOTEOFF</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR NOSAVE>
|
||
|
|
<TD NOSAVE>KEYPRESS</TD>
|
||
|
|
|
||
|
|
<TD>MIDI_KEY_PRESSURE</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR NOSAVE>
|
||
|
|
<TD>CHANPRESS</TD>
|
||
|
|
|
||
|
|
<TD NOSAVE>SEQ_AFTERTOUCH
|
||
|
|
<BR>MIDI_CHN_PRESSURE</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR NOSAVE>
|
||
|
|
<TD NOSAVE>PGMCHANGE</TD>
|
||
|
|
|
||
|
|
<TD NOSAVE>SEQ_PGMCHANGE
|
||
|
|
<BR>MIDI_PGM_CHANGE</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>PITCHBEND</TD>
|
||
|
|
|
||
|
|
<TD>SEQ_CONTROLLER(CTRL_PITCH_BENDER)
|
||
|
|
<BR>MIDI_PITCH_BEND</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>CONTROLLER</TD>
|
||
|
|
|
||
|
|
<TD>MIDI_CTL_CHANGE
|
||
|
|
<BR>SEQ_BALANCE (with CTL_PAN)</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>CONTROL14</TD>
|
||
|
|
|
||
|
|
<TD>SEQ_CONTROLLER</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>REGPARAM</TD>
|
||
|
|
|
||
|
|
<TD>SEQ_CONTROLLER(CTRL_PITCH_BENDER_RANGE)</TD>
|
||
|
|
</TR>
|
||
|
|
|
||
|
|
<TR>
|
||
|
|
<TD>SYSEX</TD>
|
||
|
|
|
||
|
|
<TD>SEQ_SYSEX</TD>
|
||
|
|
</TR>
|
||
|
|
</TABLE>
|
||
|
|
|
||
|
|
<P>The most of these behavior can be realized by MIDI emulation driver
|
||
|
|
included in the Emu8000 lowlevel driver. In the future release, this module
|
||
|
|
will be independent.
|
||
|
|
<P>Some OSS events (<TT>SEQ_PRIVATE</TT> and <TT>SEQ_VOLUME</TT> events) are passed as event
|
||
|
|
type SND_SEQ_OSS_PRIVATE. The OSS sequencer passes these event 8 byte
|
||
|
|
packets without any modification. The lowlevel driver should process these
|
||
|
|
events appropriately.
|
||
|
|
<H2>
|
||
|
|
8. Interface to MIDI Device</H2>
|
||
|
|
Since the OSS emulation probes the creation and deletion of ALSA MIDI sequencer
|
||
|
|
ports automatically by receiving announcement from ALSA sequencer, the
|
||
|
|
MIDI devices don't need to be registered explicitly like synth devices.
|
||
|
|
However, the MIDI port_info registered to ALSA sequencer must include a group
|
||
|
|
name <TT>SND_SEQ_GROUP_DEVICE</TT> and a capability-bit <TT>CAP_READ</TT> or
|
||
|
|
<TT>CAP_WRITE</TT>. Also, subscription capabilities, <TT>CAP_SUBS_READ</TT> or <TT>CAP_SUBS_WRITE</TT>,
|
||
|
|
must be defined, too. If these conditions are not satisfied, the port is not
|
||
|
|
registered as OSS sequencer MIDI device.
|
||
|
|
<P>The events via MIDI devices are parsed in OSS sequencer and converted
|
||
|
|
to the corresponding ALSA sequencer events. The input from MIDI sequencer
|
||
|
|
is also converted to MIDI byte events by OSS sequencer. This works just
|
||
|
|
a reverse way of seq_midi module.
|
||
|
|
<H2>
|
||
|
|
9. Known Problems / TODO's</H2>
|
||
|
|
|
||
|
|
<UL>
|
||
|
|
<LI>
|
||
|
|
Patch loading via ALSA instrument layer is not implemented yet.</LI>
|
||
|
|
</UL>
|
||
|
|
|
||
|
|
</BODY>
|
||
|
|
</HTML>
|