Implement letterbox-only blackbar detection mode (#1063)

CHANGELOG.md

@@ -15,7 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - New LED Device SK9822 (#1005)
 - Support SK9822 type LEDs with adaptive brightness control via SPI (#1017)
 - Provide additional details on Hardware/CPU information (#1045)
-- Allow execution with option "--version", while another hyperion daemon is running
+Allow execution with option "--version", while another hyperion daemon is running
+- New blackbar detection mode "Letterbox", that considers only bars at the top and bottom of picture
 - Systray icons added - Issue #925 (#1040)
 - DirectX9 Grabber (#1039)
 - Added DirectX SDK to CompileHowto

assets/webconfig/i18n/en.json

@@ -261,6 +261,7 @@
     "edt_conf_enum_automatic": "Automatic",
     "edt_conf_enum_bbclassic": "Classic",
     "edt_conf_enum_bbdefault": "Default",
+    "edt_conf_enum_bbletterbox": "Letterbox",
     "edt_conf_enum_bbosd": "OSD",
     "edt_conf_enum_bgr": "BGR",
     "edt_conf_enum_bottom_up": "Bottom up",

config/hyperion.config.json.commented

@@ -178,7 +178,7 @@
 	///  * borderFrameCnt     : Number of frames before a consistent detected border gets set (default 50)
 	///  * maxInconsistentCnt : Number of inconsistent frames that are ignored before a new border gets a chance to proof consistency
 	///  * blurRemoveCnt      : Number of pixels that get removed from the detected border to cut away blur (default 1)
-	///  * mode               : Border detection mode (values=default,classic,osd)
+	///  * mode               : Border detection mode (values=default,classic,osd,letterbox)
 	"blackborderdetector" :
 	{
 		"enable"             : true,

docs/docs/en/user/advanced/Advanced.md

@@ -93,6 +93,7 @@ Explain the differences between the available modes for blackbar detection.
   * **Default:** 3 scanlines in each direction (X Y) - fastest detection
   * **Classic:** The original implementation - lower cpu time (legacy for RPi 1) just scan the top one third of the picture which leads to a  slow detection and trouble with TV channel logo.
   * **OSD:** Based on the default mode - not that effective but prevents border switching which may caused of OSD overlays (program infos and volume bar).
+  * **Letterbox:** Based on the default mode - only considers blackbars at the top and bottom of the picture, ignoring the sides.
 <ImageWrap src="/images/en/user_bbmodes.jpg" alt="Hyperion Blackbar detection modes" />
 
 ## Gamma Curve

include/blackborder/BlackBorderDetector.h

@@ -234,6 +234,49 @@ namespace hyperion
 		}
 
 
+		///
+		/// letterbox detection mode (5lines top-bottom only detection)
+		template <typename Pixel_T>
+		BlackBorder process_letterbox(const Image<Pixel_T> & image) const
+		{
+			// test center and 25%, 75% of width
+			// 25 and 75 will check both top and bottom
+			// center will only check top (minimise false detection of captions)
+			int width = image.width();
+			int height = image.height();
+			int width25percent = width / 4;
+			int height33percent = height / 3;
+			int width75percent = width25percent * 3;
+			int xCenter = width / 2;
+
+
+			int firstNonBlackYPixelIndex = -1;
+
+			height--; // remove 1 pixel to get end pixel index
+
+			// find first Y pixel of the image
+			for (int y = 0; y < height33percent; ++y)
+			{
+				if (!isBlack(image(xCenter, y))
+					|| !isBlack(image(width25percent, y))
+					|| !isBlack(image(width75percent, y))
+					|| !isBlack(image(width25percent, (height - y)))
+					|| !isBlack(image(width75percent, (height - y))))
+				{
+					firstNonBlackYPixelIndex = y;
+					break;
+				}
+			}
+
+			// Construct result
+			BlackBorder detectedBorder;
+			detectedBorder.unknown = firstNonBlackYPixelIndex == -1;
+			detectedBorder.horizontalSize = firstNonBlackYPixelIndex;
+			detectedBorder.verticalSize = 0;
+			return detectedBorder;
+		}
+
+
 
 	private:
 

include/blackborder/BlackBorderProcessor.h

@@ -79,6 +79,8 @@ namespace hyperion
 				imageBorder = _detector->process_classic(image);
 			} else if (_detectionMode == "osd") {
 				imageBorder = _detector->process_osd(image);
+			} else if (_detectionMode == "letterbox") {
+				imageBorder = _detector->process_letterbox(image);
 			}
 			// add blur to the border
 			if (imageBorder.horizontalSize > 0)

libsrc/hyperion/schema/schema-blackborderdetector.json

@@ -60,10 +60,10 @@
 		{
 			"type" : "string",
 			"title": "edt_conf_bb_mode_title",
-			"enum" : ["default", "classic", "osd"],
+			"enum" : ["default", "classic", "osd", "letterbox"],
 			"default" : "default",
 			"options" : {
-				"enum_titles" : ["edt_conf_enum_bbdefault", "edt_conf_enum_bbclassic", "edt_conf_enum_bbosd"]
+				"enum_titles" : ["edt_conf_enum_bbdefault", "edt_conf_enum_bbclassic", "edt_conf_enum_bbosd", "edt_conf_enum_bbletterbox"]
 			},
 			"propertyOrder" : 7
 		}