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Object Hierarchy
GObject ╰── GInitiallyUnowned ╰── GstObject ╰── GstElement ╰── GstBaseTransform ╰── GstVideoFilter ╰── GstCairoOverlay
Description
cairooverlay renders an overlay using a application provided render function.
The full example can be found in tests/examples/cairo/cairo_overlay.c
Example code
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#include <gst/gst.h> #include <gst/video/video.h> ... typedef struct { gboolean valid; int width; int height; } CairoOverlayState; ... static void prepare_overlay (GstElement * overlay, GstCaps * caps, gpointer user_data) { CairoOverlayState *state = (CairoOverlayState *)user_data; gst_video_format_parse_caps (caps, NULL, &state->width, &state->height); state->valid = TRUE; } static void draw_overlay (GstElement * overlay, cairo_t * cr, guint64 timestamp, guint64 duration, gpointer user_data) { CairoOverlayState *s = (CairoOverlayState *)user_data; double scale; if (!s->valid) return; scale = 2*(((timestamp/(int)1e7) % 70)+30)/100.0; cairo_translate(cr, s->width/2, (s->height/2)-30); cairo_scale (cr, scale, scale); cairo_move_to (cr, 0, 0); cairo_curve_to (cr, 0,-30, -50,-30, -50,0); cairo_curve_to (cr, -50,30, 0,35, 0,60 ); cairo_curve_to (cr, 0,35, 50,30, 50,0 ); * cairo_curve_to (cr, 50,-30, 0,-30, 0,0 ); cairo_set_source_rgba (cr, 0.9, 0.0, 0.1, 0.7); cairo_fill (cr); } ... cairo_overlay = gst_element_factory_make ("cairooverlay", "overlay"); g_signal_connect (cairo_overlay, "draw", G_CALLBACK (draw_overlay), overlay_state); g_signal_connect (cairo_overlay, "caps-changed", G_CALLBACK (prepare_overlay), overlay_state); ... |
Synopsis
Element Pads
name |
sink |
direction |
sink |
presence |
always |
details |
video/x-raw, format=(string){ BGRx, BGRA, RGB16 }, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ] |
name |
src |
direction |
source |
presence |
always |
details |
video/x-raw, format=(string){ BGRx, BGRA, RGB16 }, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ] |
Signal Details
The “caps-changed” signal
void user_function (GstCairoOverlay *overlay, GstCaps *caps, gpointer user_data)
This signal is emitted when the caps of the element has changed.
Parameters
overlay |
Overlay element emitting the signal. |
|
caps |
The GstCaps of the element. |
|
user_data |
user data set when the signal handler was connected. |
The “draw” signal
void user_function (GstCairoOverlay *overlay, CairoContext *cr, guint64 timestamp, guint64 duration, gpointer user_data)
This signal is emitted when the overlay should be drawn.
Parameters
overlay |
Overlay element emitting the signal. |
|
cr |
Cairo context to draw to. |
|
timestamp |
Timestamp (see GstClockTime) of the current buffer. |
|
duration |
Duration (see GstClockTime) of the current buffer. |
|
user_data |
user data set when the signal handler was connected. |