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Mixer group control structure
typedef struct snd_mixer_group_s
{
snd_mixer_gid_t gid;
uint32_t caps;
uint32_t channels;
int32_t min, max;
union
{
int32_t values[32];
struct
{
int32_t front_left;
int32_t front_right;
int32_t front_center;
int32_t rear_left;
int32_t rear_right;
int32_t woofer;
uint8_t reserved[128]; /* must be filled with zero */
} names;
} volume;
uint32_t mute;
uint32_t capture;
int32_t capture_group;
int32_t elements_size, elements, elements_over;
snd_mixer_eid_t *pelements;
void *pzero; /* align pointers on 64-bits --> point to NULL */
uint8_t reserved[128]; /* must be filled with zero */
} snd_mixer_group_t;
The snd_mixer_group_t structure is the control structure for a
mixer group.
You can get the information for a group by calling
snd_mixer_group_read(),
and set it by calling
snd_mixer_group_write().
The members of this structure include:
- gid
- A
snd_mixer_gid_t
structure that identifies the group.
This structure includes the group name and index.
- caps
- The capabilities of the group, expressed through any combination of
these flags:
- SND_MIXER_GRPCAP_VOLUME — the group has at least
one volume control.
- SND_MIXER_GRPCAP_JOINTLY_VOLUME — all channel
volume levels for the group must be the same (ganged).
- SND_MIXER_GRPCAP_MUTE — the group has at least one
mute control.
- SND_MIXER_GRPCAP_JOINTLY_MUTE — all channel mute
settings for the group must be the same (ganged).
- SND_MIXER_GRPCAP_CAPTURE — the group can be
captured (recorded).
- SND_MIXER_GRPCAP_JOINTLY_CAPTURE — all channel
capture settings for the group must be the same (ganged).
- SND_MIXER_GRPCAP_EXCL_CAPTURE — only one
group on this device can be captured at a time.
- SND_MIXER_GRPCAP_PLAY_GRP — the group is a
playback group.
- SND_MIXER_GRPCAP_CAP_GRP — the group is a capture
group.
- SND_MIXER_GRPCAP_SUBCHANNEL — the group is a
subchannel control.
It exists only while a PCM subchannel is allocated by an application.
- channels
- The mapped bits that correspond to the channels contained in
this group.
For example, for stereo right and left speakers, bits 1 and 2 (00011) are mapped;
for the center speaker, bit 3 (00100) is mapped.
- min, max
- The minimum and maximum values that define the volume range.
Note that the minimum doesn't have to be zero.
- volume
- A structure that contains the volume level for each channel in the group.
You can access the values accessed directly by name or indirectly through
the array of values.
|
If the group is jointly volumed, all volume values must be the
same; setting different values results in undefined behavior.
|
- mute
- The mute state of the group channels.
If the bit corresponding to the channel is set, the channel is muted.
|
If the group is jointly muted, all mute bits must be the same; setting the
bits differently results in undefined behavior.
|
- capture
- The capture state of the group channels.
If the bit corresponding to the channel is set, the channel is being
captured.
If the group is exclusively capture, setting capture on this group
means that another group is no longer being captured.
|
If the group is jointly captured, all capture bits must be the same;
setting the bits differently results in undefined behavior.
|
- capture_group
- Not currently used.
- elements_size
- The size of the memory block pointed to by pelements in
units of snd_mixer_eid_t.
- elements
- The number of element IDs that are currently valid in pelements.
- elements_over
- The number of element IDs that were not returned in pelements
because it wasn't large enough.
- pelements
- A pointer to a region of memory (allocated by the calling
application) that's used to store an array of element IDs.
This is an array of
snd_mixer_eid_t
structures.
The elements that are returned are the component elements that make
up the group identified by gid.
QNX Neutrino
snd_mixer_eid_t,
snd_mixer_gid_t,
snd_mixer_group_read(),
snd_mixer_group_write()
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