avcodec/ass: accurately preserve colours

Colour values used in ASS files without a "YCbCr Matrix" header set to
"None" are subject to colour mangling, due to how ASS was historically
conceived. A more in-depth description can be found in the documetation
inside libass' public ass_types.h header. The important part is, if this
header is not set to "None", the final output colours can deviate from
the literal value specified in the file. When converting from non-ASS
formats we do not want any colour shift to happen, so let's set the
appropiate header.

NB: ffmpeg's subtitle filter, does not follow libass' documentation
regarding colour mangling, thus hiding the bug. Anything based on
VSFilter, XySubFilter or e.g. mpv do and might show the issue.
(Of course native ASS subs, which _do_ rely on colour mangling won't
 work properly with the subtitle filter, but this can be fixed another
 time)

libavcodec/ass.c

@@ -41,6 +41,7 @@ int ff_ass_subtitle_header_full(AVCodecContext *avctx,
              "PlayResX: %d\r\n"
              "PlayResY: %d\r\n"
              "ScaledBorderAndShadow: yes\r\n"
+             "YCbCr Matrix: None\r\n"
              "\r\n"
              "[V4+ Styles]\r\n"
 

tests/ref/fate/sub-aqtitle

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-cc

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-cc-realtime

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-cc-scte20

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-charenc

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-jacosub

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-microdvd

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-movtext

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-mpl2

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-mpsub

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-mpsub-frames

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-pjs

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-realtext

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-sami

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-sami2

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-scc

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-srt

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-srt-badsyntax

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-stl

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-subviewer

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-subviewer1

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-vplayer

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-webvtt

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding

tests/ref/fate/sub-webvtt2

@@ -4,6 +4,7 @@ ScriptType: v4.00+
 PlayResX: 384
 PlayResY: 288
 ScaledBorderAndShadow: yes
+YCbCr Matrix: None
 
 [V4+ Styles]
 Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding