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gstreamer/subprojects/gst-plugins-base/ext/pango/gstbasetextoverlay.h
Nirbheek Chauhan a1463637e0 pango: Add a property to compensate for display response time 
When measuring video latency, one mechanism involves taking a photo
with a camera of two screens showing the test video overlayed with
timeoverlay or clockoverlay. In these cases, if the display's pixel
response time is crappy, you will see ghosting due to which it can be
quite difficult to discern what the current timestamp being shown is.

This commit adds a property that *also* shows the timestamp in
a different (sequentially predictable) location every frame, which
makes it easy to tell what the latest rendered timestamp is.

For bonus points, you can also use the fade-time of the previous frame
to measure with sub-framerate accuracy when the photo was taken, not
just clamped to the framerate, giving you a higher precision latency
value.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6935>
2024-06-06 14:03:04 +00:00

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/* GStreamer
* Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
* Copyright (C) <2003> David Schleef <ds@schleef.org>
* Copyright (C) <2006> Julien Moutte <julien@moutte.net>
* Copyright (C) <2006> Zeeshan Ali <zeeshan.ali@nokia.com>
* Copyright (C) <2006-2008> Tim-Philipp Müller <tim centricular net>
* Copyright (C) <2009> Young-Ho Cha <ganadist@gmail.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#ifndef __GST_BASE_TEXT_OVERLAY_H__
#define __GST_BASE_TEXT_OVERLAY_H__
#include <gst/gst.h>
#include <gst/video/video.h>
#include <gst/video/video-overlay-composition.h>
#include <pango/pangocairo.h>
G_BEGIN_DECLS
#define GST_TYPE_BASE_TEXT_OVERLAY (gst_base_text_overlay_get_type())
#define GST_BASE_TEXT_OVERLAY(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj),\
GST_TYPE_BASE_TEXT_OVERLAY, GstBaseTextOverlay))
#define GST_BASE_TEXT_OVERLAY_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass),\
GST_TYPE_BASE_TEXT_OVERLAY,GstBaseTextOverlayClass))
#define GST_BASE_TEXT_OVERLAY_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj),\
GST_TYPE_BASE_TEXT_OVERLAY, GstBaseTextOverlayClass))
#define GST_IS_BASE_TEXT_OVERLAY(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj),\
GST_TYPE_BASE_TEXT_OVERLAY))
#define GST_IS_BASE_TEXT_OVERLAY_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass),\
GST_TYPE_BASE_TEXT_OVERLAY))
typedef struct _GstBaseTextOverlay GstBaseTextOverlay;
typedef struct _GstBaseTextOverlayClass GstBaseTextOverlayClass;
/**
* GstBaseTextOverlayVAlign:
* @GST_BASE_TEXT_OVERLAY_VALIGN_BASELINE: draw text on the baseline
* @GST_BASE_TEXT_OVERLAY_VALIGN_BOTTOM: draw text on the bottom
* @GST_BASE_TEXT_OVERLAY_VALIGN_TOP: draw text on top
* @GST_BASE_TEXT_OVERLAY_VALIGN_POS: draw text according to the #GstBaseTextOverlay:ypos property
* @GST_BASE_TEXT_OVERLAY_VALIGN_CENTER: draw text vertically centered
*
* Vertical alignment of the text.
*/
typedef enum {
GST_BASE_TEXT_OVERLAY_VALIGN_BASELINE,
GST_BASE_TEXT_OVERLAY_VALIGN_BOTTOM,
GST_BASE_TEXT_OVERLAY_VALIGN_TOP,
GST_BASE_TEXT_OVERLAY_VALIGN_POS,
GST_BASE_TEXT_OVERLAY_VALIGN_CENTER,
GST_BASE_TEXT_OVERLAY_VALIGN_ABSOLUTE
} GstBaseTextOverlayVAlign;
/**
* GstBaseTextOverlayHAlign:
* @GST_BASE_TEXT_OVERLAY_HALIGN_LEFT: align text left
* @GST_BASE_TEXT_OVERLAY_HALIGN_CENTER: align text center
* @GST_BASE_TEXT_OVERLAY_HALIGN_RIGHT: align text right
* @GST_BASE_TEXT_OVERLAY_HALIGN_POS: position text according to the #GstBaseTextOverlay:xpos property
*
* Horizontal alignment of the text.
*/
/* FIXME 0.11: remove GST_BASE_TEXT_OVERLAY_HALIGN_UNUSED */
typedef enum {
GST_BASE_TEXT_OVERLAY_HALIGN_LEFT,
GST_BASE_TEXT_OVERLAY_HALIGN_CENTER,
GST_BASE_TEXT_OVERLAY_HALIGN_RIGHT,
GST_BASE_TEXT_OVERLAY_HALIGN_UNUSED,
GST_BASE_TEXT_OVERLAY_HALIGN_POS,
GST_BASE_TEXT_OVERLAY_HALIGN_ABSOLUTE
} GstBaseTextOverlayHAlign;
/**
* GstBaseTextOverlayWrapMode:
* @GST_BASE_TEXT_OVERLAY_WRAP_MODE_NONE: no wrapping
* @GST_BASE_TEXT_OVERLAY_WRAP_MODE_WORD: do word wrapping
* @GST_BASE_TEXT_OVERLAY_WRAP_MODE_CHAR: do char wrapping
* @GST_BASE_TEXT_OVERLAY_WRAP_MODE_WORD_CHAR: do word and char wrapping
*
* Whether to wrap the text and if so how.
*/
typedef enum {
GST_BASE_TEXT_OVERLAY_WRAP_MODE_NONE = -1,
GST_BASE_TEXT_OVERLAY_WRAP_MODE_WORD = PANGO_WRAP_WORD,
GST_BASE_TEXT_OVERLAY_WRAP_MODE_CHAR = PANGO_WRAP_CHAR,
GST_BASE_TEXT_OVERLAY_WRAP_MODE_WORD_CHAR = PANGO_WRAP_WORD_CHAR
} GstBaseTextOverlayWrapMode;
/**
* GstBaseTextOverlayLineAlign:
* @GST_BASE_TEXT_OVERLAY_LINE_ALIGN_LEFT: lines are left-aligned
* @GST_BASE_TEXT_OVERLAY_LINE_ALIGN_CENTER: lines are center-aligned
* @GST_BASE_TEXT_OVERLAY_LINE_ALIGN_RIGHT: lines are right-aligned
*
* Alignment of text lines relative to each other
*/
typedef enum {
GST_BASE_TEXT_OVERLAY_LINE_ALIGN_LEFT = PANGO_ALIGN_LEFT,
GST_BASE_TEXT_OVERLAY_LINE_ALIGN_CENTER = PANGO_ALIGN_CENTER,
GST_BASE_TEXT_OVERLAY_LINE_ALIGN_RIGHT = PANGO_ALIGN_RIGHT
} GstBaseTextOverlayLineAlign;
/**
* GstBaseTextOverlayScaleMode:
* @GST_BASE_TEXT_OVERLAY_SCALE_MODE_NONE: no compensation
* @GST_BASE_TEXT_OVERLAY_SCALE_MODE_PAR: compensate pixel-aspect-ratio scaling
* @GST_BASE_TEXT_OVERLAY_SCALE_MODE_DISPLAY: compensate for scaling to display (as determined by overlay allocation meta)
* @GST_BASE_TEXT_OVERLAY_SCALE_MODE_USER: compensate scaling set by #GstBaseTextOverlay:scale-pixel-aspect-ratio property
*
* Scale text to compensate for and avoid aspect distortion by subsequent
* scaling of video
*/
typedef enum {
GST_BASE_TEXT_OVERLAY_SCALE_MODE_NONE,
GST_BASE_TEXT_OVERLAY_SCALE_MODE_PAR,
GST_BASE_TEXT_OVERLAY_SCALE_MODE_DISPLAY,
GST_BASE_TEXT_OVERLAY_SCALE_MODE_USER
} GstBaseTextOverlayScaleMode;
/**
* GstBaseTextOverlay:
*
* Opaque textoverlay object structure
*/
struct _GstBaseTextOverlay {
GstElement element;
GstPad *video_sinkpad;
GstPad *text_sinkpad;
GstPad *srcpad;
PangoContext *pango_context;
GstSegment segment;
GstSegment text_segment;
GstBuffer *text_buffer;
GstClockTime text_buffer_running_time;
GstClockTime text_buffer_running_time_end;
gboolean text_linked;
gboolean video_flushing;
gboolean video_eos;
gboolean text_flushing;
gboolean text_eos;
GMutex lock;
GCond cond; /* to signal removal of a queued text
* buffer, arrival of a text buffer,
* a text segment update, or a change
* in status (e.g. shutdown, flushing) */
/* stream metrics */
GstVideoInfo info;
GstVideoFormat format;
gint width;
gint height;
/* properties */
gint xpad;
gint ypad;
gint deltax;
gint deltay;
gdouble xpos;
gdouble ypos;
gchar *default_text;
gboolean want_shading;
gboolean silent;
gboolean wait_text;
guint color, outline_color;
PangoLayout *layout;
gboolean auto_adjust_size;
gboolean draw_shadow;
gboolean draw_outline;
gint shading_value; /* for timeoverlay subclass */
gboolean use_vertical_render;
GstBaseTextOverlayVAlign valign;
GstBaseTextOverlayHAlign halign;
GstBaseTextOverlayWrapMode wrap_mode;
GstBaseTextOverlayLineAlign line_align;
GstBaseTextOverlayScaleMode scale_mode;
gint scale_par_n;
gint scale_par_d;
gboolean alt_render;
/* text pad format */
gboolean have_pango_markup;
/* rendering state */
gboolean need_render;
GstBuffer *text_image;
/* dimension relative to witch the render is done, this is the stream size
* or a portion of the window_size (adapted to aspect ratio) */
gint render_width;
gint render_height;
/* This is (render_width / width) uses to convert to stream scale */
gdouble render_scale;
/* dimension of text_image, the physical dimension */
guint text_width;
guint text_height;
/* position of rendering in image coordinates */
gint text_x;
gint text_y;
/* window dimension, reported in the composition meta params. This is set
* to stream width, height if missing */
gint window_width;
gint window_height;
gdouble shadow_offset;
gdouble outline_offset;
PangoRectangle ink_rect;
PangoRectangle logical_rect;
gboolean attach_compo_to_buffer;
GstVideoOverlayComposition *composition;
GstVideoOverlayComposition *upstream_composition;
};
struct _GstBaseTextOverlayClass {
GstElementClass parent_class;
gchar * (*get_text) (GstBaseTextOverlay *overlay, GstBuffer *video_frame);
};
GType gst_base_text_overlay_get_type(void) G_GNUC_CONST;
G_END_DECLS
#endif /* __GST_BASE_TEXT_OVERLAY_H */
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