Functions to create and handle overlay compositions on video buffers.

An overlay composition describes one or more overlay rectangles to be blended on top of a video buffer.

This API serves two main purposes:

gst_video_overlay_composition_new ()

GstVideoOverlayComposition *
gst_video_overlay_composition_new (GstVideoOverlayRectangle *rectangle);

Creates a new video overlay composition object to hold one or more overlay rectangles.

gst_video_overlay_composition_ref ()

GstVideoOverlayComposition *
gst_video_overlay_composition_ref (GstVideoOverlayComposition *comp);

Increases the refcount of the given composition by one.

Note that the refcount affects the writeability of comp , use gst_video_overlay_composition_make_writable() to ensure a composition and its rectangles can be modified.

gst_video_overlay_composition_unref ()

void
gst_video_overlay_composition_unref (GstVideoOverlayComposition *comp);

Decreases the refcount of the composition. If the refcount reaches 0, the composition will be freed.

gst_video_overlay_composition_add_rectangle ()

void
gst_video_overlay_composition_add_rectangle
                               (GstVideoOverlayComposition *comp,
                                GstVideoOverlayRectangle *rectangle);

Adds an overlay rectangle to an existing overlay composition object. This must be done right after creating the overlay composition.

gst_video_overlay_composition_n_rectangles ()

guint
gst_video_overlay_composition_n_rectangles
                               (GstVideoOverlayComposition *comp);

Returns the number of GstVideoOverlayRectangles contained in comp .

gst_video_overlay_composition_get_rectangle ()

GstVideoOverlayRectangle *
gst_video_overlay_composition_get_rectangle
                               (GstVideoOverlayComposition *comp,
                                guint n);

Returns the n -th GstVideoOverlayRectangle contained in comp .

gst_video_overlay_composition_get_seqnum ()

guint
gst_video_overlay_composition_get_seqnum
                               (GstVideoOverlayComposition *comp);

Returns the sequence number of this composition. Sequence numbers are monotonically increasing and unique for overlay compositions and rectangles (meaning there will never be a rectangle with the same sequence number as a composition).

gst_video_overlay_composition_copy ()

GstVideoOverlayComposition *
gst_video_overlay_composition_copy (GstVideoOverlayComposition *comp);

Makes a copy of comp and all contained rectangles, so that it is possible to modify the composition and contained rectangles (e.g. add additional rectangles or change the render co-ordinates or render dimension). The actual overlay pixel data buffers contained in the rectangles are not copied.

gst_video_overlay_composition_make_writable ()

GstVideoOverlayComposition *
gst_video_overlay_composition_make_writable
                               (GstVideoOverlayComposition *comp);

Takes ownership of comp and returns a version of comp that is writable (i.e. can be modified). Will either return comp right away, or create a new writable copy of comp and unref comp itself. All the contained rectangles will also be copied, but the actual overlay pixel data buffers contained in the rectangles are not copied.

gst_video_overlay_composition_blend ()

gboolean
gst_video_overlay_composition_blend (GstVideoOverlayComposition *comp,
                                     GstVideoFrame *video_buf);

Blends the overlay rectangles in comp on top of the raw video data contained in video_buf . The data in video_buf must be writable and mapped appropriately.

Since video_buf data is read and will be modified, it ought be mapped with flag GST_MAP_READWRITE.

gst_video_overlay_composition_meta_get_info ()

const GstMetaInfo *
gst_video_overlay_composition_meta_get_info
                               (void);

gst_buffer_add_video_overlay_composition_meta ()

GstVideoOverlayCompositionMeta *
gst_buffer_add_video_overlay_composition_meta
                               (GstBuffer *buf,
                                GstVideoOverlayComposition *comp);

Sets an overlay composition on a buffer. The buffer will obtain its own reference to the composition, meaning this function does not take ownership of comp .

gst_buffer_get_video_overlay_composition_meta()

#define             gst_buffer_get_video_overlay_composition_meta(b)

gst_buffer_remove_video_overlay_composition_meta()

#define             gst_buffer_remove_video_overlay_composition_meta(b,m)

gst_video_overlay_rectangle_new_raw ()

GstVideoOverlayRectangle *
gst_video_overlay_rectangle_new_raw (GstBuffer *pixels,
                                     gint render_x,
                                     gint render_y,
                                     guint render_width,
                                     guint render_height,
                                     GstVideoOverlayFormatFlags flags);

Creates a new video overlay rectangle with ARGB or AYUV pixel data. The layout in case of ARGB of the components in memory is B-G-R-A on little-endian platforms (corresponding to GST_VIDEO_FORMAT_BGRA) and A-R-G-B on big-endian platforms (corresponding to GST_VIDEO_FORMAT_ARGB). In other words, pixels are treated as 32-bit words and the lowest 8 bits then contain the blue component value and the highest 8 bits contain the alpha component value. Unless specified in the flags, the RGB values are non-premultiplied. This is the format that is used by most hardware, and also many rendering libraries such as Cairo, for example. The pixel data buffer must have GstVideoMeta set.

gst_video_overlay_rectangle_ref ()

GstVideoOverlayRectangle *
gst_video_overlay_rectangle_ref (GstVideoOverlayRectangle *comp);

Increases the refcount of the given rectangle by one.

Note that the refcount affects the writeability of comp , use gst_video_overlay_rectangle_copy() to ensure a rectangle can be modified (there is no gst_video_overlay_rectangle_make_writable() because it is unlikely that someone will hold the single reference to the rectangle and not know that that's the case).

gst_video_overlay_rectangle_unref ()

void
gst_video_overlay_rectangle_unref (GstVideoOverlayRectangle *comp);

Decreases the refcount of the rectangle. If the refcount reaches 0, the rectangle will be freed.

gst_video_overlay_rectangle_get_pixels_raw ()

GstBuffer *
gst_video_overlay_rectangle_get_pixels_raw
                               (GstVideoOverlayRectangle *rectangle,
                                GstVideoOverlayFormatFlags flags);

gst_video_overlay_rectangle_get_pixels_argb ()

GstBuffer *
gst_video_overlay_rectangle_get_pixels_argb
                               (GstVideoOverlayRectangle *rectangle,
                                GstVideoOverlayFormatFlags flags);

gst_video_overlay_rectangle_get_pixels_ayuv ()

GstBuffer *
gst_video_overlay_rectangle_get_pixels_ayuv
                               (GstVideoOverlayRectangle *rectangle,
                                GstVideoOverlayFormatFlags flags);

gst_video_overlay_rectangle_get_pixels_unscaled_raw ()

GstBuffer *
gst_video_overlay_rectangle_get_pixels_unscaled_raw
                               (GstVideoOverlayRectangle *rectangle,
                                GstVideoOverlayFormatFlags flags);

Retrieves the pixel data as it is. This is useful if the caller can do the scaling itself when handling the overlaying. The rectangle will need to be scaled to the render dimensions, which can be retrieved using gst_video_overlay_rectangle_get_render_rectangle().

gst_video_overlay_rectangle_get_pixels_unscaled_argb ()

GstBuffer *
gst_video_overlay_rectangle_get_pixels_unscaled_argb
                               (GstVideoOverlayRectangle *rectangle,
                                GstVideoOverlayFormatFlags flags);

Retrieves the pixel data as it is. This is useful if the caller can do the scaling itself when handling the overlaying. The rectangle will need to be scaled to the render dimensions, which can be retrieved using gst_video_overlay_rectangle_get_render_rectangle().

gst_video_overlay_rectangle_get_pixels_unscaled_ayuv ()

GstBuffer *
gst_video_overlay_rectangle_get_pixels_unscaled_ayuv
                               (GstVideoOverlayRectangle *rectangle,
                                GstVideoOverlayFormatFlags flags);

Retrieves the pixel data as it is. This is useful if the caller can do the scaling itself when handling the overlaying. The rectangle will need to be scaled to the render dimensions, which can be retrieved using gst_video_overlay_rectangle_get_render_rectangle().

gst_video_overlay_rectangle_get_render_rectangle ()

gboolean
gst_video_overlay_rectangle_get_render_rectangle
                               (GstVideoOverlayRectangle *rectangle,
                                gint *render_x,
                                gint *render_y,
                                guint *render_width,
                                guint *render_height);

Retrieves the render position and render dimension of the overlay rectangle on the video.

gst_video_overlay_rectangle_get_seqnum ()

guint
gst_video_overlay_rectangle_get_seqnum
                               (GstVideoOverlayRectangle *rectangle);

Returns the sequence number of this rectangle. Sequence numbers are monotonically increasing and unique for overlay compositions and rectangles (meaning there will never be a rectangle with the same sequence number as a composition).

Using the sequence number of a rectangle as an indicator for changed pixel-data of a rectangle is dangereous. Some API calls, like e.g. gst_video_overlay_rectangle_set_global_alpha(), automatically update the per rectangle sequence number, which is misleading for renderers/ consumers, that handle global-alpha themselves. For them the pixel-data returned by gst_video_overlay_rectangle_get_pixels_*() wont be different for different global-alpha values. In this case a renderer could also use the GstBuffer pointers as a hint for changed pixel-data.

gst_video_overlay_rectangle_set_render_rectangle ()

void
gst_video_overlay_rectangle_set_render_rectangle
                               (GstVideoOverlayRectangle *rectangle,
                                gint render_x,
                                gint render_y,
                                guint render_width,
                                guint render_height);

Sets the render position and dimensions of the rectangle on the video. This function is mainly for elements that modify the size of the video in some way (e.g. through scaling or cropping) and need to adjust the details of any overlays to match the operation that changed the size.

rectangle must be writable, meaning its refcount must be 1. You can make the rectangles inside a GstVideoOverlayComposition writable using gst_video_overlay_composition_make_writable() or gst_video_overlay_composition_copy().

gst_video_overlay_rectangle_copy ()

GstVideoOverlayRectangle *
gst_video_overlay_rectangle_copy (GstVideoOverlayRectangle *rectangle);

Makes a copy of rectangle , so that it is possible to modify it (e.g. to change the render co-ordinates or render dimension). The actual overlay pixel data buffers contained in the rectangle are not copied.

gst_video_overlay_rectangle_get_flags ()

GstVideoOverlayFormatFlags
gst_video_overlay_rectangle_get_flags (GstVideoOverlayRectangle *rectangle);

Retrieves the flags associated with a GstVideoOverlayRectangle. This is useful if the caller can handle both premultiplied alpha and non premultiplied alpha, for example. By knowing whether the rectangle uses premultiplied or not, it can request the pixel data in the format it is stored in, to avoid unnecessary conversion.

gst_video_overlay_rectangle_get_global_alpha ()

gfloat
gst_video_overlay_rectangle_get_global_alpha
                               (GstVideoOverlayRectangle *rectangle);

Retrieves the global-alpha value associated with a GstVideoOverlayRectangle.

gst_video_overlay_rectangle_set_global_alpha ()

void
gst_video_overlay_rectangle_set_global_alpha
                               (GstVideoOverlayRectangle *rectangle,
                                gfloat global_alpha);

Sets the global alpha value associated with a GstVideoOverlayRectangle. Per- pixel alpha values are multiplied with this value. Valid values: 0 <= global_alpha <= 1; 1 to deactivate.

rectangle must be writable, meaning its refcount must be 1. You can make the rectangles inside a GstVideoOverlayComposition writable using gst_video_overlay_composition_make_writable() or gst_video_overlay_composition_copy().

GstVideoOverlayComposition

typedef struct _GstVideoOverlayComposition GstVideoOverlayComposition;

An opaque video overlay composition object. A composition contains multiple overlay rectangles.

GST_VIDEO_OVERLAY_COMPOSITION_BLEND_FORMATS

#define             GST_VIDEO_OVERLAY_COMPOSITION_BLEND_FORMATS

Video formats supported by gst_video_overlay_composition_blend(), for use in overlay elements' pad template caps.

Since: 1.2

struct GstVideoOverlayCompositionMeta

struct GstVideoOverlayCompositionMeta {
  GstMeta meta;

  GstVideoOverlayComposition *overlay;
};

Extra buffer metadata describing image overlay data.

enum GstVideoOverlayFormatFlags

Overlay format flags.

GstVideoOverlayRectangle

typedef struct _GstVideoOverlayRectangle GstVideoOverlayRectangle;

An opaque video overlay rectangle object. A rectangle contains a single overlay rectangle which can be added to a composition.