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1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
2 | <HTML> | |
3 | <HEAD> | |
4 | <TITLE>OSS Sequencer Emulation on ALSA</TITLE> | |
5 | </HEAD> | |
6 | <BODY> | |
7 | ||
8 | <CENTER> | |
9 | <H1> | |
10 | ||
11 | <HR WIDTH="100%"></H1></CENTER> | |
12 | ||
13 | <CENTER> | |
14 | <H1> | |
15 | OSS Sequencer Emulation on ALSA</H1></CENTER> | |
16 | ||
17 | <HR WIDTH="100%"> | |
18 | <P>Copyright (c) 1998,1999 by Takashi Iwai | |
19 | <TT><A HREF="mailto:iwai@ww.uni-erlangen.de"><iwai@ww.uni-erlangen.de></A></TT> | |
20 | <P>ver.0.1.8; Nov. 16, 1999 | |
21 | <H2> | |
22 | ||
23 | <HR WIDTH="100%"></H2> | |
24 | ||
25 | <H2> | |
26 | 1. Description</H2> | |
27 | This directory contains the OSS sequencer emulation driver on ALSA. Note | |
28 | that this program is still in the development state. | |
29 | <P>What this does - it provides the emulation of the OSS sequencer, access | |
30 | via | |
31 | <TT>/dev/sequencer</TT> and <TT>/dev/music</TT> devices. | |
32 | The most of applications using OSS can run if the appropriate ALSA | |
33 | sequencer is prepared. | |
34 | <P>The following features are emulated by this driver: | |
35 | <UL> | |
36 | <LI> | |
37 | Normal sequencer and MIDI events:</LI> | |
38 | ||
39 | <BR>They are converted to the ALSA sequencer events, and sent to the corresponding | |
40 | port. | |
41 | <LI> | |
42 | Timer events:</LI> | |
43 | ||
44 | <BR>The timer is not selectable by ioctl. The control rate is fixed to | |
45 | 100 regardless of HZ. That is, even on Alpha system, a tick is always | |
46 | 1/100 second. The base rate and tempo can be changed in <TT>/dev/music</TT>. | |
47 | ||
48 | <LI> | |
49 | Patch loading:</LI> | |
50 | ||
51 | <BR>It purely depends on the synth drivers whether it's supported since | |
52 | the patch loading is realized by callback to the synth driver. | |
53 | <LI> | |
54 | I/O controls:</LI> | |
55 | ||
56 | <BR>Most of controls are accepted. Some controls | |
57 | are dependent on the synth driver, as well as even on original OSS.</UL> | |
58 | Furthermore, you can find the following advanced features: | |
59 | <UL> | |
60 | <LI> | |
61 | Better queue mechanism:</LI> | |
62 | ||
63 | <BR>The events are queued before processing them. | |
64 | <LI> | |
65 | Multiple applications:</LI> | |
66 | ||
67 | <BR>You can run two or more applications simultaneously (even for OSS sequencer)! | |
68 | However, each MIDI device is exclusive - that is, if a MIDI device is opened | |
69 | once by some application, other applications can't use it. No such a restriction | |
70 | in synth devices. | |
71 | <LI> | |
72 | Real-time event processing:</LI> | |
73 | ||
74 | <BR>The events can be processed in real time without using out of bound | |
75 | ioctl. To switch to real-time mode, send ABSTIME 0 event. The followed | |
76 | events will be processed in real-time without queued. To switch off the | |
77 | real-time mode, send RELTIME 0 event. | |
78 | <LI> | |
79 | <TT>/proc</TT> interface:</LI> | |
80 | ||
81 | <BR>The status of applications and devices can be shown via <TT>/proc/asound/seq/oss</TT> | |
82 | at any time. In the later version, configuration will be changed via <TT>/proc</TT> | |
83 | interface, too.</UL> | |
84 | ||
85 | <H2> | |
86 | 2. Installation</H2> | |
87 | Run configure script with both sequencer support (<TT>--with-sequencer=yes</TT>) | |
88 | and OSS emulation (<TT>--with-oss=yes</TT>) options. A module <TT>snd-seq-oss.o</TT> | |
89 | will be created. If the synth module of your sound card supports for OSS | |
90 | emulation (so far, only Emu8000 driver), this module will be loaded automatically. | |
91 | Otherwise, you need to load this module manually. | |
92 | <P>At beginning, this module probes all the MIDI ports which have been | |
93 | already connected to the sequencer. Once after that, the creation and deletion | |
94 | of ports are watched by announcement mechanism of ALSA sequencer. | |
95 | <P>The available synth and MIDI devices can be found in proc interface. | |
96 | Run "<TT>cat /proc/asound/seq/oss</TT>", and check the devices. For example, | |
97 | if you use an AWE64 card, you'll see like the following: | |
98 | <PRE> OSS sequencer emulation version 0.1.8 | |
99 | ALSA client number 63 | |
100 | ALSA receiver port 0 | |
101 | ||
102 | Number of applications: 0 | |
103 | ||
104 | Number of synth devices: 1 | |
105 | ||
106 | synth 0: [EMU8000] | |
107 | type 0x1 : subtype 0x20 : voices 32 | |
108 | capabilties : ioctl enabled / load_patch enabled | |
109 | ||
110 | Number of MIDI devices: 3 | |
111 | ||
112 | midi 0: [Emu8000 Port-0] ALSA port 65:0 | |
113 | capability write / opened none | |
114 | ||
115 | midi 1: [Emu8000 Port-1] ALSA port 65:1 | |
116 | capability write / opened none | |
117 | ||
118 | midi 2: [0: MPU-401 (UART)] ALSA port 64:0 | |
119 | capability read/write / opened none</PRE> | |
120 | Note that the device number may be different from the information of | |
121 | <TT>/proc/asound/oss-devices</TT> | |
122 | or ones of the original OSS driver. Use the device number listed in <TT>/proc/asound/seq/oss</TT> | |
123 | to play via OSS sequencer emulation. | |
124 | <H2> | |
125 | 3. Using Synthesizer Devices</H2> | |
126 | Run your favorite program. I've tested playmidi-2.4, awemidi-0.4.3, gmod-3.1 | |
127 | and xmp-1.1.5. You can load samples via <TT>/dev/sequencer</TT> like sfxload, | |
128 | too. | |
129 | <P>If the lowlevel driver supports multiple access to synth devices (like | |
130 | Emu8000 driver), two or more applications are allowed to run at the same | |
131 | time. | |
132 | <H2> | |
133 | 4. Using MIDI Devices</H2> | |
134 | So far, only MIDI output was tested. MIDI input was not checked at all, | |
135 | but hopefully it will work. Use the device number listed in <TT>/proc/asound/seq/oss</TT>. | |
136 | Be aware that these numbers are mostly different from the list in | |
137 | <TT>/proc/asound/oss-devices</TT>. | |
138 | <H2> | |
139 | 5. Module Options</H2> | |
140 | The following module options are available: | |
141 | <UL> | |
142 | <LI> | |
143 | <TT>maxqlen</TT></LI> | |
144 | ||
145 | <BR>specifies the maximum read/write queue length. This queue is private | |
146 | for OSS sequencer, so that it is independent from the queue length of ALSA | |
147 | sequencer. Default value is 1024. | |
148 | <LI> | |
149 | <TT>seq_oss_debug</TT></LI> | |
150 | ||
151 | <BR>specifies the debug level and accepts zero (= no debug message) or | |
152 | positive integer. Default value is 0.</UL> | |
153 | ||
154 | <H2> | |
155 | 6. Queue Mechanism</H2> | |
156 | OSS sequencer emulation uses an ALSA priority queue. The | |
157 | events from <TT>/dev/sequencer</TT> are processed and put onto the queue | |
158 | specified by module option. | |
159 | <P>All the events from <TT>/dev/sequencer</TT> are parsed at beginning. | |
160 | The timing events are also parsed at this moment, so that the events may | |
161 | be processed in real-time. Sending an event ABSTIME 0 switches the operation | |
162 | mode to real-time mode, and sending an event RELTIME 0 switches it off. | |
163 | In the real-time mode, all events are dispatched immediately. | |
164 | <P>The queued events are dispatched to the corresponding ALSA sequencer | |
165 | ports after scheduled time by ALSA sequencer dispatcher. | |
166 | <P>If the write-queue is full, the application sleeps until a certain amount | |
167 | (as default one half) becomes empty in blocking mode. The synchronization | |
168 | to write timing was implemented, too. | |
169 | <P>The input from MIDI devices or echo-back events are stored on read FIFO | |
170 | queue. If application reads <TT>/dev/sequencer</TT> in blocking mode, the | |
171 | process will be awaked. | |
172 | ||
173 | <H2> | |
174 | 7. Interface to Synthesizer Device</H2> | |
175 | ||
176 | <H3> | |
177 | 7.1. Registration</H3> | |
178 | To register an OSS synthesizer device, use <TT>snd_seq_oss_synth_register</TT> | |
179 | function. | |
180 | <PRE>int snd_seq_oss_synth_register(char *name, int type, int subtype, int nvoices, | |
181 | snd_seq_oss_callback_t *oper, void *private_data)</PRE> | |
182 | The arguments <TT>name</TT>, <TT>type</TT>, <TT>subtype</TT> and | |
183 | <TT>nvoices</TT> | |
184 | are used for making the appropriate synth_info structure for ioctl. The | |
185 | return value is an index number of this device. This index must be remembered | |
186 | for unregister. If registration is failed, -errno will be returned. | |
187 | <P>To release this device, call <TT>snd_seq_oss_synth_unregister function</TT>: | |
188 | <PRE>int snd_seq_oss_synth_unregister(int index),</PRE> | |
189 | where the <TT>index</TT> is the index number returned by register function. | |
190 | <H3> | |
191 | 7.2. Callbacks</H3> | |
192 | OSS synthesizer devices have capability for sample downloading and ioctls | |
193 | like sample reset. In OSS emulation, these special features are realized | |
194 | by using callbacks. The registration argument oper is used to specify these | |
195 | callbacks. The following callback functions must be defined: | |
196 | <PRE>snd_seq_oss_callback_t: | |
197 | int (*open)(snd_seq_oss_arg_t *p, void *closure); | |
198 | int (*close)(snd_seq_oss_arg_t *p); | |
199 | int (*ioctl)(snd_seq_oss_arg_t *p, unsigned int cmd, unsigned long arg); | |
200 | int (*load_patch)(snd_seq_oss_arg_t *p, int format, const char *buf, int offs, int count); | |
201 | int (*reset)(snd_seq_oss_arg_t *p); | |
202 | Except for <TT>open</TT> and <TT>close</TT> callbacks, they are allowed | |
203 | to be NULL. | |
204 | <P>Each callback function takes the argument type snd_seq_oss_arg_t as the | |
205 | first argument. | |
206 | <PRE>struct snd_seq_oss_arg_t { | |
207 | int app_index; | |
208 | int file_mode; | |
209 | int seq_mode; | |
210 | snd_seq_addr_t addr; | |
211 | void *private_data; | |
212 | int event_passing; | |
213 | };</PRE> | |
214 | The first three fields, <TT>app_index</TT>, <TT>file_mode</TT> and | |
215 | <TT>seq_mode</TT> | |
216 | are initialized by OSS sequencer. The <TT>app_index</TT> is the application | |
217 | index which is unique to each application opening OSS sequencer. The | |
218 | <TT>file_mode</TT> | |
219 | is bit-flags indicating the file operation mode. See | |
220 | <TT>seq_oss.h</TT> | |
221 | for its meaning. The <TT>seq_mode</TT> is sequencer operation mode. In | |
222 | the current version, only <TT>SND_OSSSEQ_MODE_SYNTH</TT> is used. | |
223 | <P>The next two fields, <TT>addr</TT> and <TT>private_data</TT>, must be | |
224 | filled by the synth driver at open callback. The <TT>addr</TT> contains | |
225 | the address of ALSA sequencer port which is assigned to this device. If | |
226 | the driver allocates memory for <TT>private_data</TT>, it must be released | |
227 | in close callback by itself. | |
228 | <P>The last field, <TT>event_passing</TT>, indicates how to translate note-on | |
229 | / off events. In <TT>PROCESS_EVENTS</TT> mode, the note 255 is regarded | |
230 | as velocity change, and key pressure event is passed to the port. In <TT>PASS_EVENTS</TT> | |
231 | mode, all note on/off events are passed to the port without modified. <TT>PROCESS_KEYPRESS</TT> | |
232 | mode checks the note above 128 and regards it as key pressure event (mainly | |
233 | for Emu8000 driver). | |
234 | <H4> | |
235 | 7.2.1. Open Callback</H4> | |
236 | The <TT>open</TT> is called at each time this device is opened by an application | |
237 | using OSS sequencer. This must not be NULL. Typically, the open callback | |
238 | does the following procedure: | |
239 | <OL> | |
240 | <LI> | |
241 | Allocate private data record.</LI> | |
242 | ||
243 | <LI> | |
244 | Create an ALSA sequencer port.</LI> | |
245 | ||
246 | <LI> | |
247 | Set the new port address on arg->addr.</LI> | |
248 | ||
249 | <LI> | |
250 | Set the private data record pointer on arg->private_data.</LI> | |
251 | </OL> | |
252 | Note that the type bit-flags in port_info of this synth port must NOT contain | |
253 | <TT>TYPE_MIDI_GENERIC</TT> | |
254 | bit. Instead, <TT>TYPE_SPECIFIC</TT> should be used. Also, <TT>CAP_SUBSCRIPTION</TT> | |
255 | bit should NOT be included, too. This is necessary to tell it from other | |
256 | normal MIDI devices. If the open procedure succeeded, return zero. Otherwise, | |
257 | return -errno. | |
258 | <H4> | |
259 | 7.2.2 Ioctl Callback</H4> | |
260 | The <TT>ioctl</TT> callback is called when the sequencer receives device-specific | |
261 | ioctls. The following two ioctls should be processed by this callback: | |
262 | <UL> | |
263 | <LI> | |
264 | <TT>IOCTL_SEQ_RESET_SAMPLES</TT></LI> | |
265 | ||
266 | <BR>reset all samples on memory -- return 0 | |
267 | <LI> | |
268 | <TT>IOCTL_SYNTH_MEMAVL</TT></LI> | |
269 | ||
270 | <BR>return the available memory size | |
271 | <LI> | |
272 | <TT>FM_4OP_ENABLE</TT></LI> | |
273 | ||
274 | <BR>can be ignored usually</UL> | |
275 | The other ioctls are processed inside the sequencer without passing to | |
276 | the lowlevel driver. | |
277 | <H4> | |
278 | 7.2.3 Load_Patch Callback</H4> | |
279 | The <TT>load_patch</TT> callback is used for sample-downloading. This callback | |
280 | must read the data on user-space and transfer to each device. Return 0 | |
281 | if succeeded, and -errno if failed. The format argument is the patch key | |
282 | in patch_info record. The buf is user-space pointer where patch_info record | |
283 | is stored. The offs can be ignored. The count is total data size of this | |
284 | sample data. | |
285 | <H4> | |
286 | 7.2.4 Close Callback</H4> | |
287 | The <TT>close</TT> callback is called when this device is closed by the | |
9ad477a1 | 288 | application. If any private data was allocated in open callback, it must |
1da177e4 LT |
289 | be released in the close callback. The deletion of ALSA port should be |
290 | done here, too. This callback must not be NULL. | |
291 | <H4> | |
292 | 7.2.5 Reset Callback</H4> | |
293 | The <TT>reset</TT> callback is called when sequencer device is reset or | |
294 | closed by applications. The callback should turn off the sounds on the | |
295 | relevant port immediately, and initialize the status of the port. If this | |
296 | callback is undefined, OSS seq sends a <TT>HEARTBEAT</TT> event to the | |
297 | port. | |
298 | <H3> | |
299 | 7.3 Events</H3> | |
300 | Most of the events are processed by sequencer and translated to the adequate | |
301 | ALSA sequencer events, so that each synth device can receive by input_event | |
302 | callback of ALSA sequencer port. The following ALSA events should be implemented | |
303 | by the driver: | |
304 | <BR> | |
305 | <TABLE BORDER WIDTH="75%" NOSAVE > | |
306 | <TR NOSAVE> | |
307 | <TD NOSAVE><B>ALSA event</B></TD> | |
308 | ||
309 | <TD><B>Original OSS events</B></TD> | |
310 | </TR> | |
311 | ||
312 | <TR> | |
313 | <TD>NOTEON</TD> | |
314 | ||
315 | <TD>SEQ_NOTEON | |
316 | <BR>MIDI_NOTEON</TD> | |
317 | </TR> | |
318 | ||
319 | <TR> | |
320 | <TD>NOTE</TD> | |
321 | ||
322 | <TD>SEQ_NOTEOFF | |
323 | <BR>MIDI_NOTEOFF</TD> | |
324 | </TR> | |
325 | ||
326 | <TR NOSAVE> | |
327 | <TD NOSAVE>KEYPRESS</TD> | |
328 | ||
329 | <TD>MIDI_KEY_PRESSURE</TD> | |
330 | </TR> | |
331 | ||
332 | <TR NOSAVE> | |
333 | <TD>CHANPRESS</TD> | |
334 | ||
335 | <TD NOSAVE>SEQ_AFTERTOUCH | |
336 | <BR>MIDI_CHN_PRESSURE</TD> | |
337 | </TR> | |
338 | ||
339 | <TR NOSAVE> | |
340 | <TD NOSAVE>PGMCHANGE</TD> | |
341 | ||
342 | <TD NOSAVE>SEQ_PGMCHANGE | |
343 | <BR>MIDI_PGM_CHANGE</TD> | |
344 | </TR> | |
345 | ||
346 | <TR> | |
347 | <TD>PITCHBEND</TD> | |
348 | ||
349 | <TD>SEQ_CONTROLLER(CTRL_PITCH_BENDER) | |
350 | <BR>MIDI_PITCH_BEND</TD> | |
351 | </TR> | |
352 | ||
353 | <TR> | |
354 | <TD>CONTROLLER</TD> | |
355 | ||
356 | <TD>MIDI_CTL_CHANGE | |
357 | <BR>SEQ_BALANCE (with CTL_PAN)</TD> | |
358 | </TR> | |
359 | ||
360 | <TR> | |
361 | <TD>CONTROL14</TD> | |
362 | ||
363 | <TD>SEQ_CONTROLLER</TD> | |
364 | </TR> | |
365 | ||
366 | <TR> | |
367 | <TD>REGPARAM</TD> | |
368 | ||
369 | <TD>SEQ_CONTROLLER(CTRL_PITCH_BENDER_RANGE)</TD> | |
370 | </TR> | |
371 | ||
372 | <TR> | |
373 | <TD>SYSEX</TD> | |
374 | ||
375 | <TD>SEQ_SYSEX</TD> | |
376 | </TR> | |
377 | </TABLE> | |
378 | ||
379 | <P>The most of these behavior can be realized by MIDI emulation driver | |
380 | included in the Emu8000 lowlevel driver. In the future release, this module | |
381 | will be independent. | |
382 | <P>Some OSS events (<TT>SEQ_PRIVATE</TT> and <TT>SEQ_VOLUME</TT> events) are passed as event | |
383 | type SND_SEQ_OSS_PRIVATE. The OSS sequencer passes these event 8 byte | |
384 | packets without any modification. The lowlevel driver should process these | |
385 | events appropriately. | |
386 | <H2> | |
387 | 8. Interface to MIDI Device</H2> | |
388 | Since the OSS emulation probes the creation and deletion of ALSA MIDI sequencer | |
389 | ports automatically by receiving announcement from ALSA sequencer, the | |
390 | MIDI devices don't need to be registered explicitly like synth devices. | |
391 | However, the MIDI port_info registered to ALSA sequencer must include a group | |
392 | name <TT>SND_SEQ_GROUP_DEVICE</TT> and a capability-bit <TT>CAP_READ</TT> or | |
393 | <TT>CAP_WRITE</TT>. Also, subscription capabilities, <TT>CAP_SUBS_READ</TT> or <TT>CAP_SUBS_WRITE</TT>, | |
394 | must be defined, too. If these conditions are not satisfied, the port is not | |
395 | registered as OSS sequencer MIDI device. | |
396 | <P>The events via MIDI devices are parsed in OSS sequencer and converted | |
397 | to the corresponding ALSA sequencer events. The input from MIDI sequencer | |
398 | is also converted to MIDI byte events by OSS sequencer. This works just | |
399 | a reverse way of seq_midi module. | |
400 | <H2> | |
401 | 9. Known Problems / TODO's</H2> | |
402 | ||
403 | <UL> | |
404 | <LI> | |
405 | Patch loading via ALSA instrument layer is not implemented yet.</LI> | |
406 | </UL> | |
407 | ||
408 | </BODY> | |
409 | </HTML> |