File descriptor returned by
To query the attributes of a video input applications initialize the
indexfield of struct v4l2_input and call the
VIDIOC_ENUMINPUTioctl 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
Identifies the input, set by the application. __u8
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 of the input, see Table 2. __u32
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.
Capture devices can have zero or more tuners (RF demodulators). When the
typeis set to
V4L2_INPUT_TYPE_TUNERthis 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.
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
This field provides status information about the input. See Table 3 for flags.
statusis only valid when this is the current input.
Reserved for future extensions. Drivers must set the array to zero.
Table 2. Input Types
1 This input uses a tuner (RF demodulator).
2 Analog baseband input, for example CVBS / Composite Video, S-Video, RGB.
Table 3. Input Status Flags
0x00000001 Attached device is off.
0x00000004 The hardware supports color decoding, but does not detect color modulation in the signal. Analog Video
0x00000100 No horizontal sync lock.
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
0x00010000 No synchronization lock.
0x00020000 No equalizer lock.
0x00040000 Carrier recovery failed. VCR and Set-Top Box
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.
0x02000000 Conditional access denied.
0x04000000 VTR time constant. [?]
On success 0 is returned, on error -1 and the
errnovariable is set appropriately:
The struct v4l2_input
indexis out of bounds.