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Get the number of elements in the mixer and their element IDs
#include <sys/asoundlib.h>
int snd_mixer_elements(
snd_mixer_t *handle,
snd_mixer_elements_t *elements );
- handle
- The handle for the mixer device.
This must have been created by
snd_mixer_open().
- elements
- A pointer to a
snd_mixer_elements_t
structure in which snd_mixer_elements() stores the information
about the elements.
libasound.so
The snd_mixer_elements() function
fills the given snd_mixer_elements_t structure with the number
of elements in the mixer
that the handle was opened on.
It also fills in the array of element IDs pointed to by pelements
to a limit of elements_size.
|
We recommend that you work with mixer groups instead of manipulating the
elements directly. |
Before calling snd_mixer_elements(), set the
snd_mixer_elements_t structure as follows:
- pelements
- This pointer be NULL, or point to a valid storage location
for the elements (i.e. an array of
snd_mixer_eid_t
structures).
- elements_size
- This must reflect the size of the pelements storage location,
in sizeof( snd_mixer_eid_t ) units
(i.e. elements_size must be the number of entries in the
pelements array).
On a successful return, snd_mixer_elements() sets these members:
- elements
- The total number of elements in the mixer.
- pelements
- If non-NULL, the mixer element IDs are filled in.
- elements_over
- The number of elements that couldn't be copied to the storage location.
Zero on success, or a negative value on error.
- -EINVAL
- Invalid handle.
QNX Neutrino
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
Yes |
Thread |
Yes |
snd_mixer_eid_t,
snd_mixer_element_read(),
snd_mixer_element_write(),
snd_mixer_elements_t,
snd_mixer_sort_eid_table()
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