v4l2src: GStreamer Good Plugins 1.0 Plugins Reference Manual

## v4l2src v4l2src |

## Properties

gchar * | device | Read / Write
gchar * | device-name | Read
GstV4l2DeviceTypeFlags | flags | Read
gint | device-fd | Read
gint | brightness | Read / Write
gint | contrast | Read / Write
gint | hue | Read / Write
gint | saturation | Read / Write
V4L2_TV_norms | norm | Read / Write
GstV4l2IOMode | io-mode | Read / Write
GstStructure * | extra-controls | Read / Write
gboolean | force-aspect-ratio | Read / Write
gchar * | pixel-aspect-ratio | Read / Write

## Signals

void | prepare-format | Run Last

## Types and Values

struct | GstV4l2Src

## Object Hierarchy

        GObject
        ╰── GInitiallyUnowned
            ╰── GstObject
                ╰── GstElement
                    ╰── GstBaseSrc
                        ╰── GstPushSrc
                            ╰── GstV4l2Src

## Implemented Interfaces

GstV4l2Src implements GstURIHandler, GstTuner, GstColorBalance and GstVideoOrientation.

## Description

v4l2src can be used to capture video from v4l2 devices, like webcams and tv cards.

### Example launch lines

    1
    gst-launch-1.0 v4l2src ! xvimagesink

This pipeline shows the video captured from /dev/video0 tv card and for webcams.

    1
    gst-launch-1.0 v4l2src ! jpegdec ! xvimagesink

This pipeline shows the video captured from a webcam that delivers jpeg images.

Since 1.14, the use of libv4l2 has been disabled due to major bugs in the emulation layer. To enable usage of this library, set the environment variable GST_V4L2_USE_LIBV4L2=1.

## Synopsis

### Element Information

plugin | video4linux2
author | Edgard Lima <edgard.lima@gmail.com>, Stefan Kost <ensonic@users.sf.net>
class | Source/Video

### Element Pads

name | src
direction | source
presence | always
details | image/jpeg
| video/mpeg, mpegversion=(int)4, systemstream=(boolean)false
| video/mpeg, mpegversion=(int)2
| video/mpegts, systemstream=(boolean)true
| video/x-bayer, format=(string){ bggr, gbrg, grbg, rggb }, width=(int)[ 1, 32768 ], height=(int)[ 1, 32768 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
| video/x-dv, systemstream=(boolean)true
| video/x-h263, variant=(string)itu
| video/x-h264, stream-format=(string){ byte-stream, avc }, alignment=(string)au
| video/x-pwc1, width=(int)[ 1, 32768 ], height=(int)[ 1, 32768 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
| video/x-pwc2, width=(int)[ 1, 32768 ], height=(int)[ 1, 32768 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
| video/x-raw, format=(string){ RGB16, BGR, RGB, GRAY8, GRAY16_LE, GRAY16_BE, YVU9, YV12, YUY2, YVYU, UYVY, Y42B, Y41B, YUV9, NV12_64Z32, NV24, NV61, NV16, NV21, NV12, I420, BGRA, BGRx, ARGB, xRGB, BGR15, RGB15 }, width=(int)[ 1, 32768 ], height=(int)[ 1, 32768 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
| video/x-sonix, width=(int)[ 1, 32768 ], height=(int)[ 1, 32768 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
| video/x-vp8
| video/x-vp9
| video/x-wmv, wmvversion=(int)3, format=(string)WVC1

## Functions

## Types and Values

### struct GstV4l2Src

    struct GstV4l2Src;

Opaque object.

## Property Details

### The `“device”` property

      “device”                   gchar *

Device location.

Flags: Read / Write

Default value: "/dev/video0"

### The `“device-name”` property

      “device-name”              gchar *

Name of the device.

Flags: Read

Default value: NULL

### The `“flags”` property

      “flags”                    GstV4l2DeviceTypeFlags

Device type flags.

Flags: Read

### The `“device-fd”` property

      “device-fd”                gint

File descriptor of the device.

Flags: Read

Allowed values: >= G_MAXULONG

Default value: -1

### The `“brightness”` property

      “brightness”               gint

Picture brightness, or more precisely, the black level

Flags: Read / Write

Default value: 0

### The `“contrast”` property

      “contrast”                 gint

Picture contrast or luma gain

Flags: Read / Write

Default value: 0

### The `“hue”` property

      “hue”                      gint

Hue or color balance

Flags: Read / Write

Default value: 0

### The `“saturation”` property

      “saturation”               gint

Picture color saturation or chroma gain

Flags: Read / Write

Default value: 0

### The `“norm”` property

      “norm”                     V4L2_TV_norms

TV norm

Flags: Read / Write

Default value: none

### The `“io-mode”` property

      “io-mode”                  GstV4l2IOMode

IO Mode

Flags: Read / Write

Default value: GST_V4L2_IO_AUTO

### The `“extra-controls”` property

      “extra-controls”           GstStructure *

Additional v4l2 controls for the device. The controls are identified by the control name (lowercase with '_' for any non-alphanumeric characters).

Flags: Read / Write

Since: 1.2

### The `“force-aspect-ratio”` property

      “force-aspect-ratio”       gboolean

When enabled, the pixel aspect ratio queried from the device or set with the pixel-aspect-ratio property will be enforced.

Flags: Read / Write

Default value: TRUE

Since: 1.2

### The `“pixel-aspect-ratio”` property

      “pixel-aspect-ratio”       gchar *

The pixel aspect ratio of the device. This overwrites the pixel aspect ratio queried from the device.

Flags: Read / Write

Default value: "1/1"

Since: 1.2

## Signal Details

### The `“prepare-format”` signal

    void
    user_function (GstV4l2Src *v4l2src,
                   gint        fd,
                   GstCaps    *caps,
                   gpointer    user_data)

This signal gets emitted before calling the v4l2 VIDIOC_S_FMT ioctl (set format). This allows for any custom configuration of the device to happen prior to the format being set. This is mostly useful for UVC H264 encoding cameras which need the H264 Probe & Commit to happen prior to the normal Probe & Commit.

#### Parameters

v4l2src | the v4l2src instance |
fd | the file descriptor of the current device |
caps | the caps of the format being set |
user_data | user data set when the signal handler was connected. |

Flags: Run Last