snd_pcm_set_output

Synopsis:

#include <sys/asoundlib.h>

int snd_pcm_set_output_class( snd_pcm_t *pcm,
                              uint32_t outputclass);

Arguments:

pcm

The handle for the PCM device, which you must have opened by calling snd_pcm_open_name(), snd_pcm_open(), or snd_pcm_open_preferred().

outputclass

The output class to set the channel to, which can be one of the following values:

SND_OUTPUT_CLASS_UKNOWN: The output channel is for an unknown type.
SND_OUTPUT_CLASS_SPEAKER: Indicates that the output channel is for speakers that are connected to the system.
SND_OUTPUT_CLASS_HEADPHONE: Indicates that the output channel is for headphones that are connected to the system.
SND_OUTPUT_CLASS_LINEOUT: Indicates that the output channel is for the line-out channel of the system.
SND_OUTPUT_CLASS_BLUETOOTH: Indicates that the output channel is for Bluetooth.
SND_OUTPUT_CLASS_TOSLINK: Indicates the output channel is for an S-Link connector.
SND_OUTPUT_CLASS_MIRACAST: Indicates that the output channel is for Miracast.
SND_NUM_OUTPUT_CLASSES: An end-of-list identifier that indicates the total number of output types recognized by this library.

Library:

libasound.so

Use the -l asound option with qcc to link against this library.

Description:

The snd_pcm_set_output_class() function sets the output class for the PCM playback device. This call is a privileged call. Applications must be root or be part of same user group as io-audio is running as. The call is used only if the audio output routing isn't controlled by the audio driver directly (e.g., an external amplifier). External applications which control the audio output routing should use this call to notify io-audio of the change.

If the operation is successful (zero is returned), the channel's state is changed to SND_PCM_STATUS_READY.

Returns:

EOK on success, EINVAL for invalid argument values passed to this function, or a negative a negative errno upon failure. The errno values are available in the errno.h file.

Errors:

-EINVAL: The state of pcm isn't valid or an the playback channel isn't ready, or the specified output class couldn't be set.
-EPERM: An application doesn't have the appropriate privileges to call this function.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Read the Caveats

Caveats:

This function is not thread safe if handle (snd_pcm_t) is used across multiple threads.