videodetect

videodetect — Detect patterns in a video signal

Properties

gboolean message Read / Write / Construct
gint pattern-count Read / Write / Construct
gint pattern-data-count Read / Write / Construct
gint pattern-height Read / Write / Construct
gdouble pattern-sensitivity Read / Write / Construct
gint pattern-width Read / Write / Construct
gint bottom-offset Read / Write / Construct
gint left-offset Read / Write / Construct
gdouble pattern-center Read / Write / Construct

Types and Values

Object Hierarchy

    GObject
    ╰── GstObject
        ╰── GstElement
            ╰── GstBaseTransform
                ╰── GstVideoFilter
                    ╰── GstVideoDetect

Description

This plugin detects “pattern-count” squares in the bottom left corner of the video frames. The squares have a width and height of respectively “pattern-width” and “pattern-height”. Even squares must be black and odd squares must be white.

When the pattern has been found, “pattern-data-count” squares after the pattern squares are read as a bitarray. White squares represent a 1 bit and black squares a 0 bit. The bitarray will will included in the element message that is posted (see below).

After the pattern has been found and the data pattern has been read, an element message called "GstVideoDetect" will be posted on the bus. If the pattern is no longer found in the frame, the same element message is posted with the have-pattern field set to FALSE. The message is only posted if the “message” property is TRUE.

The message's structure contains these fields:

  • gboolean "have-pattern": if the pattern was found. This field will be set to TRUE for as long as the pattern was found in the frame and set to FALSE for the first frame that does not contain the pattern anymore.

  • GstClockTime "timestamp": the timestamp of the buffer that triggered the message.

  • GstClockTime "stream-time": the stream time of the buffer.

  • GstClockTime "running-time": the running_time of the buffer.

  • GstClockTime "duration": the duration of the buffer.

  • guint64 "data-uint64": the data-pattern found after the pattern or 0 when have-signal is FALSE.

  • guint "data": the data-pattern found after the pattern or 0 when have-signal is FALSE.

Example launch line

1
gst-launch videotestsrc ! videodetect ! ffmpegcolorspace ! ximagesink

Last reviewed on 2007-05-30 (0.10.5)

Synopsis

Element Information

plugin

videosignal

author

Wim Taymans <wim@fluendo.com>

class

Filter/Effect/Video

Element Pads

name

sink

direction

sink

presence

always

details

video/x-raw-yuv, format=(fourcc){ I420, YV12, Y41B, Y42B, Y444, YUY2, UYVY, AYUV, YVYU }, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]

name

src

direction

source

presence

always

details

video/x-raw-yuv, format=(fourcc){ I420, YV12, Y41B, Y42B, Y444, YUY2, UYVY, AYUV, YVYU }, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]

Functions

Types and Values

struct GstVideoDetect

struct GstVideoDetect;

Opaque datastructure.

Property Details

The “message” property

  “message”                  gboolean

Post statics messages.

Flags: Read / Write / Construct

Default value: TRUE


The “pattern-count” property

  “pattern-count”            gint

The number of pattern markers.

Flags: Read / Write / Construct

Allowed values: >= 0

Default value: 4


The “pattern-data-count” property

  “pattern-data-count”       gint

The number of extra data pattern markers.

Flags: Read / Write / Construct

Allowed values: >= 0

Default value: 5


The “pattern-height” property

  “pattern-height”           gint

The height of the pattern markers.

Flags: Read / Write / Construct

Allowed values: >= 1

Default value: 16


The “pattern-sensitivity” property

  “pattern-sensitivity”      gdouble

The sensitivity around the center for detecting the markers (0.0 = lowest, 1.0 highest).

Flags: Read / Write / Construct

Allowed values: [0,1]

Default value: 0.3


The “pattern-width” property

  “pattern-width”            gint

The width of the pattern markers.

Flags: Read / Write / Construct

Allowed values: >= 1

Default value: 4


The “bottom-offset” property

  “bottom-offset”            gint

The offset from the bottom border where the pattern starts.

Flags: Read / Write / Construct

Allowed values: >= 0

Default value: 0


The “left-offset” property

  “left-offset”              gint

The offset from the left border where the pattern starts.

Flags: Read / Write / Construct

Allowed values: >= 0

Default value: 0


The “pattern-center” property

  “pattern-center”           gdouble

The center of the black/white separation (0.0 = lowest, 1.0 highest).

Flags: Read / Write / Construct

Allowed values: [0,1]

Default value: 0.5

See Also

GstVideoMark