cea708overlay: support changing the safe title area

By default it is 80% of the output size as recommended by CEA-708/608.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1985>

docs/plugins/gst_plugins_cache.json

@@ -7984,6 +7984,34 @@
                         "type": "gint",
                         "writable": true
                     },
+                    "safe-title-height": {
+                        "blurb": "Ratio of the video height to use as the safe area for caption display",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "0.8",
+                        "max": "1",
+                        "min": "0",
+                        "mutable": "playing",
+                        "readable": true,
+                        "type": "gfloat",
+                        "writable": true
+                    },
+                    "safe-title-width": {
+                        "blurb": "Ratio of the video width to use as the safe area for caption display",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "0.8",
+                        "max": "1",
+                        "min": "0",
+                        "mutable": "playing",
+                        "readable": true,
+                        "type": "gfloat",
+                        "writable": true
+                    },
                     "service": {
                         "blurb": "The service to render the caption for when available, (-1=automatic, 0=disabled)",
                         "conditionally-available": false,

video/closedcaption/src/ccutils.rs

@@ -157,8 +157,6 @@ pub(crate) fn recalculate_pango_layout(
     video_height: u32,
 ) -> (i32, i32) {
     let mut font_desc = pango::FontDescription::from_string("monospace");
-    let video_width = video_width * 80 / 100;
-    let video_height = video_height * 80 / 100;
 
     let mut font_size = 1;
     loop {

video/closedcaption/src/cea608utils.rs

@@ -494,6 +494,11 @@ pub struct Cea608Renderer {
     video_height: u32,
     left_alignment: i32,
     black_background: bool,
+
+    safe_width: f32,
+    safe_height: f32,
+    max_layout_width: i32,
+    max_layout_height: i32,
 }
 
 impl Cea608Renderer {
@@ -506,6 +511,7 @@ impl Cea608Renderer {
         context.set_base_dir(pango::Direction::Ltr);
         let layout = pango::Layout::new(&context);
         layout.set_alignment(pango::Alignment::Left);
+        let (max_layout_width, max_layout_height) =
             recalculate_pango_layout(&layout, video_width, video_height);
         Self {
             frame: Cea608Frame::new(),
@@ -517,6 +523,10 @@ impl Cea608Renderer {
             video_height,
             left_alignment: 0,
             black_background: false,
+            safe_width: 0.8,
+            safe_height: 0.8,
+            max_layout_width,
+            max_layout_height,
         }
     }
 
@@ -546,14 +556,30 @@ impl Cea608Renderer {
         if width != self.video_width || height != self.video_height {
             self.video_width = width;
             self.video_height = height;
+            self.recalculate_window_position();
+        }
+    }
+
+    pub fn set_safe_title_area(&mut self, safe_width: f32, safe_height: f32) {
+        if safe_width != self.safe_width || safe_height != self.safe_height {
+            self.safe_width = safe_width;
+            self.safe_height = safe_height;
+            self.recalculate_window_position();
+        }
+    }
+
+    fn recalculate_window_position(&mut self) {
         self.layout = pango::Layout::new(&self.context);
         self.layout.set_alignment(pango::Alignment::Left);
-            let (max_layout_width, _max_layout_height) =
+        let width = (self.video_width as f32 * self.safe_width) as u32;
+        let height = (self.video_height as f32 * self.safe_height) as u32;
+        let (max_layout_width, max_layout_height) =
             recalculate_pango_layout(&self.layout, width, height);
-            self.left_alignment = (width as i32 - max_layout_width) / 2;
+        self.left_alignment = (self.video_width as i32 - max_layout_width) / 2;
+        self.max_layout_width = max_layout_width;
+        self.max_layout_height = max_layout_height;
         self.rectangle.take();
     }
-    }
 
     pub fn set_black_background(&mut self, bg: bool) {
         self.black_background = bg;
@@ -670,7 +696,6 @@ impl Cea608Renderer {
         let (_ink_rect, logical_rect) = self.layout.extents();
         let height = logical_rect.height() / pango::SCALE;
         let width = logical_rect.width() / pango::SCALE;
-        gst::debug!(CAT, "overlaying size {width}x{height}, text {text}");
 
         // No text actually needs rendering
         if width == 0 || height == 0 {
@@ -756,16 +781,24 @@ impl Cea608Renderer {
             }
         };
 
-        let vertical_padding = self.video_height / 10;
-        let safe_height = self.video_height.mul_div_floor(80, 100).unwrap();
-        let first_row_position = (safe_height as i32)
+        let safe_height = (self.video_height as f32 * self.safe_height) as i32;
+        let vertical_padding =
+            (2 * self.video_height as i32 - safe_height - self.max_layout_height) / 2;
+        let first_row_position = self
+            .max_layout_height
             .mul_div_round(first_row as i32, MAX_ROW as i32 + 1)
             .unwrap();
 
+        gst::debug!(
+            CAT,
+            "overlay size {width}x{height} at {}x{}, text {text}",
+            self.left_alignment,
+            first_row_position + vertical_padding
+        );
         let rect = gst_video::VideoOverlayRectangle::new_raw(
             &buffer,
             self.left_alignment,
-            first_row_position + vertical_padding as i32,
+            first_row_position + vertical_padding,
             width as u32,
             height as u32,
             gst_video::VideoOverlayFormatFlags::PREMULTIPLIED_ALPHA,

video/closedcaption/src/cea708overlay/imp.rs

@@ -28,6 +28,8 @@ static CAT: LazyLock<gst::DebugCategory> = LazyLock::new(|| {
 
 const DEFAULT_CEA608_CHANNEL: i32 = -1;
 const DEFAULT_SERVICE: i32 = 1;
+const DEFAULT_SAFE_WIDTH: f32 = 0.8;
+const DEFAULT_SAFE_HEIGHT: f32 = 0.8;
 
 #[derive(Debug, Clone)]
 struct Settings {
@@ -35,6 +37,8 @@ struct Settings {
     cea608_channel: i32,
     service: i32,
     timeout: Option<gst::ClockTime>,
+    safe_width: f32,
+    safe_height: f32,
 }
 
 impl Default for Settings {
@@ -44,6 +48,8 @@ impl Default for Settings {
             cea608_channel: DEFAULT_CEA608_CHANNEL,
             service: DEFAULT_SERVICE,
             timeout: gst::ClockTime::NONE,
+            safe_width: DEFAULT_SAFE_WIDTH,
+            safe_height: DEFAULT_SAFE_HEIGHT,
         }
     }
 }
@@ -131,6 +137,9 @@ impl Cea708Overlay {
         );
 
         state.cea708_renderer.set_service_channel(state.selected);
+        state
+            .cea708_renderer
+            .set_safe_title_area(settings.safe_width, settings.safe_height);
         settings.changed = false;
     }
 
@@ -437,9 +446,12 @@ impl Cea708Overlay {
                 true
             }
             EventView::FlushStop(..) => {
+                let settings = self.settings.lock().unwrap().clone();
                 let mut state = self.state.lock().unwrap();
                 state.cea708_renderer = Cea708Renderer::new();
-                //state.cea608_renderer.set_black_background(settings.black_background);
+                state
+                    .cea708_renderer
+                    .set_safe_title_area(settings.safe_width, settings.safe_height);
                 drop(state);
 
                 gst::Pad::event_default(pad, Some(&*self.obj()), event)
@@ -518,6 +530,22 @@ impl ObjectImpl for Cea708Overlay {
                     .default_value(u64::MAX)
                     .mutable_playing()
                     .build(),
+                glib::ParamSpecFloat::builder("safe-title-height")
+                    .nick("Safe Title Height")
+                    .blurb("Ratio of the video height to use as the safe area for caption display")
+                    .minimum(0.0)
+                    .maximum(1.0)
+                    .default_value(0.8)
+                    .mutable_playing()
+                    .build(),
+                glib::ParamSpecFloat::builder("safe-title-width")
+                    .nick("Safe Title Width")
+                    .blurb("Ratio of the video width to use as the safe area for caption display")
+                    .minimum(0.0)
+                    .maximum(1.0)
+                    .default_value(0.8)
+                    .mutable_playing()
+                    .build(),
             ]
         });
 
@@ -554,28 +582,42 @@ impl ObjectImpl for Cea708Overlay {
                     _ => Some(timeout.nseconds()),
                 };
             }
+            "safe-title-width" => {
+                let mut settings = self.settings.lock().unwrap();
+
+                let new = value.get().expect("type checked upstream");
+                if new != settings.safe_width {
+                    settings.safe_width = new;
+                    settings.changed = true;
+                }
+            }
+            "safe-title-height" => {
+                let mut settings = self.settings.lock().unwrap();
+
+                let new = value.get().expect("type checked upstream");
+                if new != settings.safe_height {
+                    settings.safe_height = new;
+                    settings.changed = true;
+                }
+            }
             _ => unimplemented!(),
         }
     }
 
     fn property(&self, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
+        let settings = self.settings.lock().unwrap();
         match pspec.name() {
-            "cea608-channel" => {
-                let settings = self.settings.lock().unwrap();
-                settings.cea608_channel.to_value()
-            }
-            "service" => {
-                let settings = self.settings.lock().unwrap();
-                settings.service.to_value()
-            }
+            "cea608-channel" => settings.cea608_channel.to_value(),
+            "service" => settings.service.to_value(),
             "timeout" => {
-                let settings = self.settings.lock().unwrap();
                 if let Some(timeout) = settings.timeout {
                     timeout.nseconds().to_value()
                 } else {
                     u64::MAX.to_value()
                 }
             }
+            "safe-title-width" => settings.safe_width.to_value(),
+            "safe-title-height" => settings.safe_height.to_value(),
             _ => unimplemented!(),
         }
     }

video/closedcaption/src/cea708utils.rs

@@ -309,6 +309,9 @@ pub struct Cea708Renderer {
     video_width: u32,
     video_height: u32,
     composition: Option<gst_video::VideoOverlayComposition>,
+
+    safe_width: f32,
+    safe_height: f32,
 }
 
 impl Cea708Renderer {
@@ -322,6 +325,8 @@ impl Cea708Renderer {
             video_width: 0,
             video_height: 0,
             composition: None,
+            safe_width: 0.8,
+            safe_height: 0.8,
         }
     }
 
@@ -337,6 +342,18 @@ impl Cea708Renderer {
         }
     }
 
+    pub fn set_safe_title_area(&mut self, safe_width: f32, safe_height: f32) {
+        if safe_width != self.safe_width || safe_height != self.safe_height {
+            self.safe_width = safe_width;
+            self.safe_height = safe_height;
+            self.cea608.set_safe_title_area(safe_width, safe_height);
+            if let Some(service) = self.service.as_mut() {
+                service.set_safe_title_area(safe_width, safe_height);
+            }
+            self.composition.take();
+        }
+    }
+
     pub fn set_service_channel(&mut self, service_channel: Option<ServiceOrChannel>) {
         if self.selected != service_channel {
             self.selected = service_channel;
@@ -353,6 +370,7 @@ impl Cea708Renderer {
             let overlay_service = self.service.get_or_insert_with(|| {
                 let mut service = ServiceState::new();
                 service.set_video_size(self.video_width, self.video_height);
+                service.set_safe_title_area(self.safe_width, self.safe_height);
                 service
             });
             overlay_service.handle_code(code);
@@ -446,6 +464,8 @@ struct ServiceState {
     pango_context: pango::Context,
     video_width: u32,
     video_height: u32,
+    width_ratio: f32,
+    height_ratio: f32,
 }
 
 impl ServiceState {
@@ -462,6 +482,8 @@ impl ServiceState {
             pango_context: context,
             video_width: 0,
             video_height: 0,
+            width_ratio: 0.8,
+            height_ratio: 0.8,
         }
     }
 
@@ -486,23 +508,20 @@ impl ServiceState {
             let layout = pango::Layout::new(&self.pango_context);
             // XXX: May need a different alignment
             layout.set_alignment(pango::Alignment::Left);
-            let mut window = Window {
-                visible: args.visible,
-                attrs: args.window_attributes(),
-                pen_attrs: args.pen_attributes(),
-                pen_color: args.pen_color(),
-                define: *args,
-                pen_location: SetPenLocationArgs::default(),
-                lines: VecDeque::new(),
-                rectangle: None,
+            self.windows.push_back(Window::new(
+                args.visible,
+                *args,
+                args.window_attributes(),
+                args.pen_attributes(),
+                args.pen_color(),
                 layout,
-                video_dims: Dimensions::default(),
-                window_position: Dimensions::default(),
-                window_dims: Dimensions::default(),
-                max_layout_dims: Dimensions::default(),
-            };
-            window.set_video_size(self.video_width, self.video_height);
-            self.windows.push_back(window);
+                Dimensions {
+                    w: self.video_width,
+                    h: self.video_height,
+                },
+                self.width_ratio,
+                self.height_ratio,
+            ));
         };
         self.current_window = args.window_id as usize;
     }
@@ -667,6 +686,14 @@ impl ServiceState {
         self.video_width = video_width;
         self.video_height = video_height;
     }
+
+    fn set_safe_title_area(&mut self, width_ratio: f32, height_ratio: f32) {
+        for window in self.windows.iter_mut() {
+            window.set_safe_title_area(width_ratio, height_ratio);
+        }
+        self.width_ratio = width_ratio;
+        self.height_ratio = height_ratio;
+    }
 }
 
 fn color_value_as_u16(val: ColorValue) -> u16 {
@@ -753,6 +780,8 @@ struct Window {
     pen_location: SetPenLocationArgs,
     lines: VecDeque<WindowLine>,
 
+    safe_width: f32,
+    safe_height: f32,
     window_position: Dimensions,
     video_dims: Dimensions,
     window_dims: Dimensions,
@@ -762,6 +791,39 @@ struct Window {
 }
 
 impl Window {
+    #[allow(clippy::too_many_arguments)]
+    fn new(
+        visible: bool,
+        define: DefineWindowArgs,
+        attrs: SetWindowAttributesArgs,
+        pen_attrs: SetPenAttributesArgs,
+        pen_color: SetPenColorArgs,
+        layout: pango::Layout,
+        video_dims: Dimensions,
+        width_ratio: f32,
+        height_ratio: f32,
+    ) -> Self {
+        let mut ret = Self {
+            visible,
+            define,
+            attrs,
+            pen_attrs,
+            pen_color,
+            pen_location: SetPenLocationArgs::default(),
+            lines: VecDeque::new(),
+            rectangle: None,
+            layout,
+            video_dims: Dimensions::default(),
+            window_position: Dimensions::default(),
+            window_dims: Dimensions::default(),
+            max_layout_dims: Dimensions::default(),
+            safe_width: width_ratio,
+            safe_height: height_ratio,
+        };
+        ret.set_video_size(video_dims.w, video_dims.h);
+        ret
+    }
+
     fn dump(&self) {
         for line in self.lines.iter() {
             let mut string = line.no.to_string();
@@ -1050,8 +1112,12 @@ impl Window {
         // XXX: may need a better implementation for 'skinny' (horizontal or vertical) output
         // sizes.
 
+        let safe_area = Dimensions {
+            w: (self.video_dims.w as f32 * self.safe_width) as u32,
+            h: (self.video_dims.h as f32 * self.safe_height) as u32,
+        };
         let (max_layout_width, max_layout_height) =
-            recalculate_pango_layout(&self.layout, self.video_dims.w, self.video_dims.h);
+            recalculate_pango_layout(&self.layout, safe_area.w, safe_area.h);
         self.max_layout_dims = Dimensions {
             w: max_layout_width as u32,
             h: max_layout_height as u32,
@@ -1067,12 +1133,8 @@ impl Window {
         };
 
         let padding = Dimensions {
-            w: self.video_dims.w / 10,
-            h: self.video_dims.h / 10,
-        };
-        let safe_area = Dimensions {
-            w: self.video_dims.w - self.video_dims.w / 5,
-            h: self.video_dims.h - self.video_dims.h / 5,
+            w: (self.video_dims.w - safe_area.w) / 2,
+            h: (self.video_dims.h - safe_area.h) / 2,
         };
 
         self.window_position = if self.define.relative_positioning {
@@ -1131,6 +1193,16 @@ impl Window {
         self.recalculate_window_position();
     }
 
+    fn set_safe_title_area(&mut self, width_ratio: f32, height_ratio: f32) {
+        if self.safe_width == width_ratio && self.safe_height == height_ratio {
+            return;
+        }
+        self.safe_width = width_ratio;
+        self.safe_height = height_ratio;
+
+        self.recalculate_window_position();
+    }
+
     fn generate_rectangle(&mut self) -> Option<gst_video::VideoOverlayRectangle> {
         if !self.visible {
             return None;