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
| __u32 | index | Identifies the input, set by the application. |
| __u8 | name[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. |
| __u32 | type | Type of the input, see Table 2. |
| __u32 | audioset | 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. |
| __u32 | tuner | Capture 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_id | std | Every 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. |
| __u32 | status | This field provides status information about the
input. See Table 3 for flags.
status is only valid when this is the
current input. |
| __u32 | reserved[4] | Reserved for future extensions. Drivers must set the array to zero. |
Table 2. Input Types
V4L2_INPUT_TYPE_TUNER | 1 | This input uses a tuner (RF demodulator). |
V4L2_INPUT_TYPE_CAMERA | 2 | Analog baseband input, for example CVBS / Composite Video, S-Video, RGB. |
Table 3. Input Status Flags
| General | ||
V4L2_IN_ST_NO_POWER | 0x00000001 | Attached device is off. |
V4L2_IN_ST_NO_SIGNAL | 0x00000002 | |
V4L2_IN_ST_NO_COLOR | 0x00000004 | The hardware supports color decoding, but does not detect color modulation in the signal. |
| Analog Video | ||
V4L2_IN_ST_NO_H_LOCK | 0x00000100 | No horizontal sync lock. |
V4L2_IN_ST_COLOR_KILL | 0x00000200 | A 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_SYNC | 0x00010000 | No synchronization lock. |
V4L2_IN_ST_NO_EQU | 0x00020000 | No equalizer lock. |
V4L2_IN_ST_NO_CARRIER | 0x00040000 | Carrier recovery failed. |
| VCR and Set-Top Box | ||
V4L2_IN_ST_MACROVISION | 0x01000000 | Macrovision 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_ACCESS | 0x02000000 | Conditional access denied. |
V4L2_IN_ST_VTR | 0x04000000 | VTR time constant. [?] |
On success 0 is returned, on error -1 and the errno variable is set appropriately:
The struct v4l2_input index is
out of bounds.