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VIDIOC_ENUMINPUT -- Enumerate video inputs


int ioctl(int fd, int request, struct v4l2_input *argp);



File descriptor returned by open().





To query the attributes of a video input applications initialize the index field of struct v4l2_input and call the VIDIOC_ENUMINPUT ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an EINVAL error code when the index is out of bounds. To enumerate all inputs applications shall begin at index zero, incrementing by one until the driver returns EINVAL.

Table 1. struct v4l2_input

__u32indexIdentifies the input, set by the application.
__u8name[32]Name of the video input, a NUL-terminated ASCII string, for example: "Vin (Composite 2)". This information is intended for the user, preferably the connector label on the device itself.
__u32typeType of the input, see Table 2.

Drivers can enumerate up to 32 video and audio inputs. This field shows which audio inputs were selectable as audio source if this was the currently selected video input. It is a bit mask. The LSB corresponds to audio input 0, the MSB to input 31. Any number of bits can be set, or none.

When the driver does not enumerate audio inputs no bits must be set. Applications shall not interpret this as lack of audio support. Some drivers automatically select audio sources and do not enumerate them since there is no choice anyway.

For details on audio inputs and how to select the current input see Section 1.5.

__u32tunerCapture devices can have zero or more tuners (RF demodulators). When the type is set to V4L2_INPUT_TYPE_TUNER this is an RF connector and this field identifies the tuner. It corresponds to struct v4l2_tuner field index. For details on tuners see Section 1.6.
v4l2_std_idstdEvery video input supports one or more different video standards. This field is a set of all supported standards. For details on video standards and how to switch see Section 1.7.
__u32statusThis field provides status information about the input. See Table 3 for flags. status is only valid when this is the current input.
__u32reserved[4]Reserved for future extensions. Drivers must set the array to zero.

Table 2. Input Types

V4L2_INPUT_TYPE_TUNER1This input uses a tuner (RF demodulator).
V4L2_INPUT_TYPE_CAMERA2Analog baseband input, for example CVBS / Composite Video, S-Video, RGB.

Table 3. Input Status Flags

V4L2_IN_ST_NO_POWER0x00000001Attached device is off.
V4L2_IN_ST_NO_COLOR0x00000004The hardware supports color decoding, but does not detect color modulation in the signal.
Analog Video
V4L2_IN_ST_NO_H_LOCK0x00000100No horizontal sync lock.
V4L2_IN_ST_COLOR_KILL0x00000200A color killer circuit automatically disables color decoding when it detects no color modulation. When this flag is set the color killer is enabled and has shut off color decoding.
Digital Video
V4L2_IN_ST_NO_SYNC0x00010000No synchronization lock.
V4L2_IN_ST_NO_EQU0x00020000No equalizer lock.
V4L2_IN_ST_NO_CARRIER0x00040000Carrier recovery failed.
VCR and Set-Top Box
V4L2_IN_ST_MACROVISION0x01000000Macrovision is an analog copy prevention system mangling the video signal to confuse video recorders. When this flag is set Macrovision has been detected.
V4L2_IN_ST_NO_ACCESS0x02000000Conditional access denied.
V4L2_IN_ST_VTR0x04000000VTR time constant. [?]

Return Value

On success 0 is returned, on error -1 and the errno variable is set appropriately:


The struct v4l2_input index is out of bounds.