2 .\" Copyright (c) 2021-2022 Christos Margiolis <christos@FreeBSD.org>
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30 .Nm mixer_get_dev_byname ,
33 .Nm mixer_remove_ctl ,
35 .Nm mixer_get_ctl_byname ,
38 .Nm mixer_mod_recsrc ,
42 .Nm mixer_get_nmixers ,
49 .Nd interface to OSS mixers
51 Mixer library (libmixer, -lmixer)
55 .Fn mixer_open "const char *name"
57 .Fn mixer_close "struct mixer *m"
59 .Fn mixer_get_dev "struct mixer *m" "int devno"
61 .Fn mixer_get_dev_byname "struct mixer *m" "name"
63 .Fn mixer_add_ctl "struct mix_dev *parent" "int id" "const char *name" \
64 "int (*mod)(struct mix_dev *d, void *p)" \
65 "int (*print)(struct mix_dev *d, void *p)"
67 .Fn mixer_add_ctl_s "mix_ctl_t *ctl"
69 .Fn mixer_remove_ctl "mix_ctl_t *ctl"
71 .Fn mixer_get_ctl "struct mix_dev *d" "int id"
73 .Fn mixer_get_ctl_byname "struct mix_dev *d" "const char *name"
75 .Fn mixer_set_vol "struct mixer *m" "mix_volume_t vol"
77 .Fn mixer_set_mute "struct mixer *m" "int opt"
79 .Fn mixer_mod_recsrc "struct mixer *m" "int opt"
81 .Fn mixer_get_dunit "void"
83 .Fn mixer_set_dunit "struct mixer *m" "int unit"
85 .Fn mixer_get_mode "int unit"
87 .Fn mixer_get_nmixers "void"
89 .Fn MIX_ISDEV "struct mixer *m" "int devno"
91 .Fn MIX_ISMUTE "struct mixer *m" "int devno"
93 .Fn MIX_ISREC "struct mixer *m" "int devno"
95 .Fn MIX_ISRECSRC "struct mixer *m" "int devno"
97 .Fn MIX_VOLNORM "int v"
99 .Fn MIX_VOLDENORM "float v"
103 library allows userspace programs to access and manipulate OSS sound mixers in
106 A mixer is described by the following structure:
109 TAILQ_HEAD(mix_devhead, mix_dev) devs; /* device list */
110 struct mix_dev *dev; /* selected device */
111 oss_mixerinfo mi; /* mixer info */
112 oss_card_info ci; /* audio card info */
113 char name[NAME_MAX]; /* mixer name (e.g /dev/mixer0) */
114 int fd; /* file descriptor */
115 int unit; /* audio card unit */
116 int ndev; /* number of devices */
117 int devmask; /* supported devices */
118 #define MIX_MUTE 0x01
119 #define MIX_UNMUTE 0x02
120 #define MIX_TOGGLEMUTE 0x04
121 int mutemask; /* muted devices */
122 int recmask; /* recording devices */
123 #define MIX_ADDRECSRC 0x01
124 #define MIX_REMOVERECSRC 0x02
125 #define MIX_SETRECSRC 0x04
126 #define MIX_TOGGLERECSRC 0x08
127 int recsrc; /* recording sources */
128 #define MIX_MODE_MIXER 0x01
129 #define MIX_MODE_PLAY 0x02
130 #define MIX_MODE_REC 0x04
131 int mode; /* dev.pcm.X.mode sysctl */
132 int f_default; /* default mixer flag */
136 The fields are follows:
137 .Bl -tag -width "f_default"
139 A tail queue structure containing all supported mixer devices.
141 A pointer to the currently selected device.
142 The device is one of the elements in
145 OSS information about the mixer.
146 Look at the definition of the
152 OSS audio card information.
153 This structure is also defined in
154 .In sys/soundcard.h .
156 Path to the mixer (e.g /dev/mixer0).
158 File descriptor returned when the mixer is opened in
162 Since each mixer device maps to a pcmX device,
164 is always equal to the number of that pcmX device.
165 For example, if the audio device's number is 0 (i.e pcm0), then
168 This number is useful when checking if the mixer's audio card is the default one.
173 Bit mask containing all supported devices for the mixer.
174 For example, if device 10 is supported, then the 10th bit in the mask will be set.
177 stores only the supported devices in devs, so it is very unlikely this mask will
180 Bit mask containing all muted devices.
181 The logic is the same as with
184 Bit mask containing all recording devices.
185 Again, same logic as with the other masks.
187 Bit mask containing all recording sources.
188 Yes, same logic again.
190 Bit mask containing the supported modes for this audio device.
191 It holds the value of the
195 Flag which tells whether the mixer's audio card is the default one.
198 Each mixer device stored in a mixer is described as follows:
201 struct mixer *parent_mixer; /* parent mixer */
202 char name[NAME_MAX]; /* device name (e.g "vol") */
203 int devno; /* device number */
205 #define MIX_VOLMIN 0.0f
206 #define MIX_VOLMAX 1.0f
207 #define MIX_VOLNORM(v) ((v) / 100.0f)
208 #define MIX_VOLDENORM(v) ((int)((v) * 100.0f + 0.5f))
209 float left; /* left volume */
210 float right; /* right volume */
212 int nctl; /* number of controls */
213 TAILQ_HEAD(mix_ctlhead, mix_ctl) ctls; /* control list */
214 TAILQ_ENTRY(mix_dev) devs;
218 The fields are follows:
219 .Bl -tag -width "parent_mixer"
221 Pointer to the mixer the device is attached to.
223 Device name given by the OSS API.
224 Devices can have one of the following names:
226 vol, bass, treble, synth, pcm, speaker, line, mic, cd, mix,
227 pcm2, rec, igain, ogain, line1, line2, line3, dig1, dig2, dig3,
228 phin, phout, video, radio, and monitor.
231 Device's index in the SOUND_MIXER_NRDEVICES macro defined in
232 .In sys/soundcard.h .
233 This number is used to check against the masks defined in the
237 Left and right-ear volumes.
238 Although the OSS API stores volumes in integers from 0-100, \
239 we normalize them to 32-bit floating point numbers.
240 However, the volumes can be denormalized using the
244 Number of user-defined mixer controls associated with the device.
246 A tail queue containing user-defined mixer controls.
248 .Ss User-defined mixer controls
249 Each mixer device can have user-defined controls.
250 The control structure is defined as follows:
253 struct mix_dev *parent_dev; /* parent device */
254 int id; /* control id */
255 char name[NAME_MAX]; /* control name */
256 int (*mod)(struct mix_dev *, void *); /* modify control values */
257 int (*print)(struct mix_dev *, void *); /* print control */
258 TAILQ_ENTRY(mix_ctl) ctls;
262 The fields are follows:
263 .Bl -tag -width "parent_dev"
265 Pointer to the device the control is attached to.
267 Control ID assigned by the caller.
268 Even though the library will report it, care has to be taken to not give \
269 a control the same ID in case the caller has to choose controls using their ID.
274 the caller has to make sure the same name is not used more than once.
276 Function pointer to a control modification function.
279 each mixer control's values can be modified.
280 For example, if we have a volume control, the
282 function will be responsible for handling volume changes.
284 Function pointer to a control print function.
286 .Ss Opening and closing the mixer
287 The application must first call the
289 function to obtain a handle to the device, which is used as an argument \
290 in most other functions and macros.
293 specifies the path to the mixer.
294 OSS mixers are stored under
298 is the number of the mixer device.
299 Each device maps to an actual
313 opens the default mixer (hw.snd.default_unit).
317 function frees resources and closes the mixer device.
318 It is a good practice to always call it when the application is done using the mixer.
319 .Ss Manipulating the mixer
323 .Fn mixer_get_dev_byname
324 functions select a mixer device, either by its number or by its name respectively.
325 The mixer structure keeps a list of all the devices, but only \
326 one can be manipulated at a time.
327 Each time a new device is to be manipulated, one of the two functions has to be called.
331 function changes the volume of the selected mixer device.
334 parameter is a structure that stores the left and right volumes of a given device.
335 The allowed volume values are between MIX_VOLMIN (0.0) and MIX_VOLMAX (1.0).
339 function modifies the mute of a selected device.
342 parameter has to be one of the following options:
343 .Bl -tag -width MIX_TOGGLEMUTE -offset indent
348 .It Dv MIX_TOGGLEMUTE
349 Toggle the device's mute (e.g mute if unmuted and unmute if muted).
354 function modifies a recording device.
355 The selected device has to be a recording device, otherwise the function will fail.
358 parameter has to be one of the following options:
359 .Bl -tag -width MIX_REMOVERECSRC -offset indent
361 Add device to the recording sources.
362 .It Dv MIX_REMOVERECSRC
363 Remove device from the recording sources.
365 Set device as the only recording source.
366 .It Dv MIX_TOGGLERECSRC
367 Toggle device from the recording sources.
374 functions get and set the default audio card in the system.
375 Although this is not really a mixer feature, it is useful to have instead of \
382 function returns the playback/recording mode of the audio device the mixer \
384 The available values are the following:
385 .Bl -tag -width "MIX_STATUS_PLAY | MIX_STATUS_REC" -offset indent
386 .It Dv MIX_STATUS_NONE
387 Neither playback nor recording.
388 .It Dv MIX_STATUS_PLAY
390 .It Dv MIX_STATUS_REC
392 .It Dv MIX_STATUS_PLAY | MIX_STATUS_REC
393 Playback and recording.
397 .Fn mixer_get_nmixers
398 function returns the total number of mixer devices in the system.
402 macro checks if a device is actually a valid device for a given mixer.
403 It is very unlikely that this macro will ever be needed since the library \
404 stores only valid devices by default.
408 macro checks if a device is muted.
412 macro checks if a device is a recording device.
416 macro checks if a device is a recording source.
420 macro normalizes a value to 32-bit floating point number.
421 It is used to normalize the volumes read from the OSS API.
425 macro denormalizes the left and right volumes stores in the
428 .Ss Defining and using mixer controls
431 function creates a control and attaches it to the device specified in the
437 function does the same thing as with
439 but the caller passes a
441 structure instead of each field as a separate argument.
445 functions removes a control from the device its attached to.
449 function searches for a control in the device specified in the
451 argument and returns a pointer to it.
452 The search is done using the control's ID.
455 .Fn mixer_get_ctl_byname
456 function is the same as with
458 but the search is done using the control's name.
462 function returns the newly created handle on success and NULL on failure.
468 .Fn mixer_mod_recsrc ,
469 .Fn mixer_get_dunut ,
472 .Fn mixer_get_nmixers
473 functions return 0 or positive values on success and -1 on failure.
478 .Fn mixer_get_dev_byname
479 functions return the selected device on success and NULL on failure.
481 All functions set the value of
485 .Ss Change the volume of a device
489 char *mix_name, *dev_name;
492 if ((m = mixer_open(mix_name)) == NULL)
493 err(1, "mixer_open: %s", mix_name);
496 if ((m->dev = mixer_get_dev_byname(m, dev_name)) < 0)
497 err(1, "unknown device: %s", dev_name);
501 if (mixer_set_vol(m, vol) < 0)
502 warn("cannot change volume");
504 (void)mixer_close(m);
506 .Ss Mute all unmuted devices
511 if ((m = mixer_open(NULL)) == NULL) /* Open the default mixer. */
512 err(1, "mixer_open");
513 TAILQ_FOREACH(dp, &m->devs, devs) {
514 m->dev = dp; /* Select device. */
515 if (M_ISMUTE(m, dp->devno))
517 if (mixer_set_mute(m, MIX_MUTE) < 0)
518 warn("cannot mute device: %s", dp->name);
521 (void)mixer_close(m);
523 .Ss Print all recording sources' names and volumes
528 char *mix_name, *dev_name;
531 if ((m = mixer_open(mix_name)) == NULL)
532 err(1, "mixer_open: %s", mix_name);
534 TAILQ_FOREACH(dp, &m->devs, devs) {
535 if (M_ISRECSRC(m, dp->devno))
536 printf("%s\\t%.2f:%.2f\\n",
537 dp->name, dp->vol.left, dp->vol.right);
540 (void)mixer_close(m);
550 .An Christos Margiolis Aq Mt christos@FreeBSD.org