7.23. ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT¶
VIDIOC_G_AUDOUT - VIDIOC_S_AUDOUT - Query or select the current audio output
int ioctl(int fd, VIDIOC_G_AUDOUT, struct v4l2_audioout *argp)
int ioctl(int fd, VIDIOC_S_AUDOUT, const struct v4l2_audioout *argp)
To query the current audio output applications zero out the
array of a struct
v4l2_audioout and call the
VIDIOC_G_AUDOUT ioctl with a pointer to this structure. Drivers fill
the rest of the structure or return an
EINVAL error code when the device
has no audio inputs, or none which combine with the current video
Audio outputs have no writable properties. Nevertheless, to select the
current audio output applications can initialize the
index field and
reserved array (which in the future may contain writable properties)
of a struct
v4l2_audioout structure and call the
VIDIOC_S_AUDOUT ioctl. Drivers switch to the requested output or
EINVAL error code when the index is out of bounds. This is a
write-only ioctl, it does not return the current audio output attributes
Connectors on a TV card to loop back the received audio signal to a sound card are not audio outputs in this sense.
Identifies the audio output, set by the driver or application.
Name of the audio output, a NUL-terminated ASCII string, for example: "Line Out". This information is intended for the user, preferably the connector label on the device itself.
Audio capability flags, none defined yet. Drivers must set this field to zero.
Audio mode, none defined yet. Drivers and applications (on
Reserved for future extensions. Drivers and applications must set the array to zero.
7.23.5. Return Value¶
On success 0 is returned, on error -1 and the
errno variable is set
appropriately. The generic error codes are described at the
Generic Error Codes chapter.
No audio outputs combine with the current video output, or the number of the selected audio output is out of bounds or it does not combine.