Fix #2149 Set colorspace and color_range ...

Set colorspace and color_range metadata on reformatted frames

When VideoFrame.reformat() is called with explicit dst_colorspace or
dst_color_range parameters, the output frame's metadata now correctly
reflects these values. Previously, the swscale conversion was performed
but the frame metadata was not updated.

Changes:
- Add SWS_CS_* to AVColorSpace mapping for correct metadata translation
- Only set frame metadata when user explicitly specifies dst parameters
- Preserve source frame metadata when dst params are not specified

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: WyattBlue

av/video/reformatter.pxd

@@ -10,4 +10,5 @@ cdef class VideoReformatter:
     cdef _reformat(self, VideoFrame frame, int width, int height,
                    lib.AVPixelFormat format, int src_colorspace,
                    int dst_colorspace, int interpolation,
-                   int src_color_range, int dst_color_range)
+                   int src_color_range, int dst_color_range,
+                   bint set_dst_colorspace, bint set_dst_color_range)

av/video/reformatter.py

@@ -58,6 +58,24 @@ def _resolve_enum_value(value, enum_class, default):
     raise ValueError(f"Cannot convert {value} to {enum_class.__name__}")
 
 
+# Mapping from SWS_CS_* (swscale colorspace) to AVColorSpace (frame metadata).
+# Note: SWS_CS_ITU601, SWS_CS_ITU624, SWS_CS_SMPTE170M, and SWS_CS_DEFAULT all have
+# the same value (5), so we map 5 -> AVCOL_SPC_SMPTE170M as the most common case.
+# SWS_CS_DEFAULT is handled specially by not setting frame metadata.
+_SWS_CS_TO_AVCOL_SPC: dict = {}  # Populated at module load time
+
+
+def _init_colorspace_map():
+    # Must be called after lib constants are available
+    _SWS_CS_TO_AVCOL_SPC[lib.SWS_CS_ITU709] = lib.AVCOL_SPC_BT709
+    _SWS_CS_TO_AVCOL_SPC[lib.SWS_CS_FCC] = lib.AVCOL_SPC_FCC
+    _SWS_CS_TO_AVCOL_SPC[lib.SWS_CS_ITU601] = lib.AVCOL_SPC_SMPTE170M
+    _SWS_CS_TO_AVCOL_SPC[lib.SWS_CS_SMPTE240M] = lib.AVCOL_SPC_SMPTE240M
+
+
+_init_colorspace_map()
+
+
 @cython.cclass
 class VideoReformatter:
     """An object for reformatting size and pixel format of :class:`.VideoFrame`.
@@ -123,6 +141,10 @@ def reformat(
             dst_color_range, ColorRange, 0
         )
 
+        # Track whether user explicitly specified destination metadata
+        set_dst_colorspace: cython.bint = dst_colorspace is not None
+        set_dst_color_range: cython.bint = dst_color_range is not None
+
         return self._reformat(
             frame,
             width or frame.ptr.width,
@@ -133,6 +155,8 @@ def reformat(
             c_interpolation,
             c_src_color_range,
             c_dst_color_range,
+            set_dst_colorspace,
+            set_dst_color_range,
         )
 
     @cython.cfunc
@@ -147,10 +171,16 @@ def _reformat(
         interpolation: cython.int,
         src_color_range: cython.int,
         dst_color_range: cython.int,
+        set_dst_colorspace: cython.bint,
+        set_dst_color_range: cython.bint,
     ):
         if frame.ptr.format < 0:
             raise ValueError("Frame does not have format set.")
 
+        # Save original values to set on the output frame (before swscale conversion)
+        frame_dst_colorspace = dst_colorspace
+        frame_dst_color_range = dst_color_range
+
         # The definition of color range in pixfmt.h and swscale.h is different.
         src_color_range = 1 if src_color_range == ColorRange.JPEG.value else 0
         dst_color_range = 1 if dst_color_range == ColorRange.JPEG.value else 0
@@ -231,6 +261,16 @@ def _reformat(
         new_frame._copy_internal_attributes(frame)
         new_frame._init(dst_format, width, height)
 
+        # Set the colorspace and color_range on the output frame only if explicitly specified
+        if set_dst_colorspace and frame_dst_colorspace in _SWS_CS_TO_AVCOL_SPC:
+            new_frame.ptr.colorspace = cython.cast(
+                lib.AVColorSpace, _SWS_CS_TO_AVCOL_SPC[frame_dst_colorspace]
+            )
+        if set_dst_color_range:
+            new_frame.ptr.color_range = cython.cast(
+                lib.AVColorRange, frame_dst_color_range
+            )
+
         with cython.nogil:
             lib.sws_scale(
                 self.ptr,