fix color normalization from bt470bg to bt709 (#1217)

CHANGELOG.md

@@ -29,6 +29,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   - Tail mode filler will properly include filler duration in XMLTV
   - Duration that wraps across midnight will no longer have overlapping items in XMLTV
 - Maintain collection progress across all alternate schedules on a playout
+- Fix color normalization from `bt470bg` to `bt709`
 
 ### Changed
 - Ignore case of video and audio file extensions in local folder scanner

ErsatzTV.FFmpeg/ColorParams.cs

@@ -3,6 +3,7 @@ namespace ErsatzTV.FFmpeg;
 public record ColorParams(string ColorRange, string ColorSpace, string ColorTransfer, string ColorPrimaries)
 {
     public static readonly ColorParams Default = new("tv", "bt709", "bt709", "bt709");
+    public static readonly ColorParams Bt470Bg = new("tv", "bt470bg", "bt470bg", "bt470bg");
     public static readonly ColorParams Unknown = new("tv", string.Empty, string.Empty, string.Empty);
 
     public bool IsHdr => ColorTransfer is "arib-std-b67" or "smpte2084";

ErsatzTV.FFmpeg/Filter/ColorspaceFilter.cs

@@ -54,8 +54,20 @@ public class ColorspaceFilter : BaseFilter
                 }
             }
 
-            string inputOverrides = string.Empty;
             ColorParams cp = _videoStream.ColorParams;
+
+            // bt470bg => bt709 seems to work correctly with `colormatrix` and NOT with `colorspace`
+            if (cp == ColorParams.Bt470Bg)
+            {
+                return _desiredPixelFormat.BitDepth switch
+                {
+                    10 => $"{hwdownload}colormatrix=dst=bt709,format=yuv420p10",
+                    8 => $"{hwdownload}colormatrix=dst=bt709,format=yuv420p",
+                    _ => string.Empty
+                };
+            }
+
+            string inputOverrides = string.Empty;
             if (cp.IsMixed || _forceInputOverrides)
             {
                 string range = string.IsNullOrWhiteSpace(cp.ColorRange) ? "tv" : cp.ColorRange;