textoverlay

textoverlay — Adds text strings on top of a video buffer

Synopsis

                    GstTextOverlay;
enum                GstTextOverlayVAlign;
enum                GstTextOverlayHAlign;
enum                GstTextOverlayWrapMode;

Object Hierarchy

  GObject
   +----GstObject
         +----GstElement
               +----GstTextOverlay
                     +----GstTimeOverlay
                     +----GstClockOverlay

Properties

  "deltax"                   gint                  : Read / Write
  "deltay"                   gint                  : Read / Write
  "font-desc"                gchar*                : Write
  "halign"                   gchar*                : Write
  "shaded-background"        gboolean              : Read / Write
  "text"                     gchar*                : Read / Write
  "valign"                   gchar*                : Write
  "wrap-mode"                GstTextOverlayWrapMode  : Read / Write
  "xpad"                     gint                  : Read / Write
  "ypad"                     gint                  : Read / Write
  "halignment"               GstTextOverlayHAlign  : Read / Write
  "valignment"               GstTextOverlayVAlign  : Read / Write
  "line-alignment"           GstTextOverlayLineAlign  : Read / Write
  "silent"                   gboolean              : Read / Write
  "wait-text"                gboolean              : Read / Write
  "auto-resize"              gboolean              : Read / Write
  "vertical-render"          gboolean              : Read / Write

Description

This plugin renders text on top of a video stream. This can be either static text or text from buffers received on the text sink pad, e.g. as produced by the subparse element. If the text sink pad is not linked, the text set via the "text" property will be rendered. If the text sink pad is linked, text will be rendered as it is received on that pad, honouring and matching the buffer timestamps of both input streams.

The text can contain newline characters and text wrapping is enabled by default.

Example launch lines

gst-launch -v videotestsrc ! textoverlay text="Room A" valign=top halign=left ! xvimagesink
Here is a simple pipeline that displays a static text in the top left corner of the video picture 
gst-launch -v filesrc location=subtitles.srt ! subparse ! txt.   videotestsrc ! timeoverlay ! textoverlay name=txt shaded-background=yes ! xvimagesink
Here is another pipeline that displays subtitles from an .srt subtitle file, centered at the bottom of the picture and with a rectangular shading around the text in the background:

If you do not have such a subtitle file, create one looking like this in a text editor: 

1
00:00:03,000 --> 00:00:05,000
Hello? (3-5s)
 
2
00:00:08,000 --> 00:00:13,000
Yes, this is a subtitle. Don't
you like it? (8-13s)
 
3
00:00:18,826 --> 00:01:02,886
Uh? What are you talking about?
I don't understand  (18-62s)

Synopsis

Element Information

plugin pango
author David Schleef <ds@schleef.org>, Zeeshan Ali <zeeshan.ali@nokia.com>
class Filter/Editor/Video

Element Pads

name text_sink
direction sink
presence always
details text/x-pango-markup
text/plain
name video_sink
direction sink
presence always
details video/x-raw-rgb, bpp=(int)32, depth=(int)24, endianness=(int)4321, red_mask=(int)65280, green_mask=(int)16711680, blue_mask=(int)-16777216, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
video/x-raw-rgb, bpp=(int)32, depth=(int)24, endianness=(int)4321, red_mask=(int)16711680, green_mask=(int)65280, blue_mask=(int)255, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
video/x-raw-yuv, format=(fourcc)I420, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
video/x-raw-yuv, format=(fourcc)UYVY, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
name src
direction source
presence always
details video/x-raw-rgb, bpp=(int)32, depth=(int)24, endianness=(int)4321, red_mask=(int)65280, green_mask=(int)16711680, blue_mask=(int)-16777216, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
video/x-raw-rgb, bpp=(int)32, depth=(int)24, endianness=(int)4321, red_mask=(int)16711680, green_mask=(int)65280, blue_mask=(int)255, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
video/x-raw-yuv, format=(fourcc)I420, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]
video/x-raw-yuv, format=(fourcc)UYVY, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]

Details

GstTextOverlay

typedef struct _GstTextOverlay GstTextOverlay;

Opaque textoverlay object structure

enum GstTextOverlayVAlign

typedef enum {
    GST_TEXT_OVERLAY_VALIGN_BASELINE,
    GST_TEXT_OVERLAY_VALIGN_BOTTOM,
    GST_TEXT_OVERLAY_VALIGN_TOP
} GstTextOverlayVAlign;

Vertical alignment of the text.

GST_TEXT_OVERLAY_VALIGN_BASELINE draw text on the baseline
GST_TEXT_OVERLAY_VALIGN_BOTTOM draw text on the bottom
GST_TEXT_OVERLAY_VALIGN_TOP draw test on top

enum GstTextOverlayHAlign

typedef enum {
    GST_TEXT_OVERLAY_HALIGN_LEFT,
    GST_TEXT_OVERLAY_HALIGN_CENTER,
    GST_TEXT_OVERLAY_HALIGN_RIGHT
} GstTextOverlayHAlign;

Horizontal alignment of the text.

GST_TEXT_OVERLAY_HALIGN_LEFT align text left
GST_TEXT_OVERLAY_HALIGN_CENTER align text center
GST_TEXT_OVERLAY_HALIGN_RIGHT align text right

enum GstTextOverlayWrapMode

typedef enum {
    GST_TEXT_OVERLAY_WRAP_MODE_NONE = -1,
    GST_TEXT_OVERLAY_WRAP_MODE_WORD = PANGO_WRAP_WORD,
    GST_TEXT_OVERLAY_WRAP_MODE_CHAR = PANGO_WRAP_CHAR,
    GST_TEXT_OVERLAY_WRAP_MODE_WORD_CHAR = PANGO_WRAP_WORD_CHAR
} GstTextOverlayWrapMode;

Whether to wrap the text and if so how.

GST_TEXT_OVERLAY_WRAP_MODE_NONE no wrapping
GST_TEXT_OVERLAY_WRAP_MODE_WORD do word wrapping
GST_TEXT_OVERLAY_WRAP_MODE_CHAR do char wrapping
GST_TEXT_OVERLAY_WRAP_MODE_WORD_CHAR do word and char wrapping

Property Details

The "deltax" property

  "deltax"                   gint                  : Read / Write

Shift X position to the left or to the right. Unit is pixels.

Default value: 0

The "deltay" property

  "deltay"                   gint                  : Read / Write

Shift Y position up or down. Unit is pixels.

Default value: 0

The "font-desc" property

  "font-desc"                gchar*                : Write

Pango font description of font to be used for rendering. See documentation of pango_font_description_from_string for syntax.

Default value: ""

The "halign" property

  "halign"                   gchar*                : Write

Horizontal alignment of the text (deprecated; use halignment).

Default value: "center"

The "shaded-background" property

  "shaded-background"        gboolean              : Read / Write

Whether to shade the background under the text area.

Default value: FALSE

The "text" property

  "text"                     gchar*                : Read / Write

Text to be display.

Default value: ""

The "valign" property

  "valign"                   gchar*                : Write

Vertical alignment of the text (deprecated; use valignment).

Default value: "baseline"

The "wrap-mode" property

  "wrap-mode"                GstTextOverlayWrapMode  : Read / Write

Whether to wrap the text and if so how.

Default value: wordchar

The "xpad" property

  "xpad"                     gint                  : Read / Write

Horizontal paddding when using left/right alignment.

Allowed values: >= 0

Default value: 25

The "ypad" property

  "ypad"                     gint                  : Read / Write

Vertical padding when using top/bottom alignment.

Allowed values: >= 0

Default value: 25

The "halignment" property

  "halignment"               GstTextOverlayHAlign  : Read / Write

Horizontal alignment of the text.

Default value: center

The "valignment" property

  "valignment"               GstTextOverlayVAlign  : Read / Write

Vertical alignment of the text.

Default value: baseline

The "line-alignment" property

  "line-alignment"           GstTextOverlayLineAlign  : Read / Write

Alignment of text lines relative to each other (for multi-line text)

Default value: center

Since 0.10.15

The "silent" property

  "silent"                   gboolean              : Read / Write

If set, no text is rendered. Useful to switch off text rendering temporarily without removing the textoverlay element from the pipeline.

Default value: FALSE

Since 0.10.15

The "wait-text" property

  "wait-text"                gboolean              : Read / Write

If set, the video will block until a subtitle is received on the text pad. If video and subtitles are sent in sync, like from the same demuxer, this property should be set.

Default value: TRUE

Since 0.10.20

The "auto-resize" property

  "auto-resize"              gboolean              : Read / Write

Automatically adjust font size to screen-size.

Default value: TRUE

The "vertical-render" property

  "vertical-render"          gboolean              : Read / Write

Vertical Render.

Default value: FALSE

See Also

GstTextRender, GstClockOverlay, GstTimeOverlay, GstSubParse
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