doc/filters: add entry for deinterlace_d3d12

Add documentation for the filter "deinterlace_d3d12" to the filters documentation.

This is the follow-up for commit https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22386/commits

Signed-off-by: younengxiao <steven.xiao@amd.com>

doc/filters.texi

@@ -11652,6 +11652,105 @@ Median
 Do not actually modify frame. Useful when one only wants metadata.
 @end table
 
+@section deinterlace_d3d12
+
+Deinterlace the input video using D3D12 hardware-accelerated video processing.
+
+This filter uses the DirectX 12 Video Processor to perform deinterlacing on
+GPU, supporting both simple bob and driver-defined advanced (motion-adaptive)
+algorithms. It requires the input to be in @code{d3d12} hardware pixel format.
+
+The filter automatically queries the hardware for the required number of
+temporal reference frames (if needed) and manages a frame queue to supply them.
+
+It accepts the following options:
+
+@table @option
+
+@item method
+The deinterlacing method. It accepts one of the following values:
+
+@table @samp
+@item default
+Select the best deinterlacing method available on the hardware.
+If the driver supports @code{custom}, that method is used; otherwise
+falls back to @code{bob}. This is the default.
+
+@item bob
+Bob deinterlacing. Each field is independently scaled to full
+frame height. Simple and fast, but may produce visible bob artifacts
+on moving content.
+
+@item custom
+Driver-defined advanced deinterlacing. The exact algorithm is
+hardware-specific and typically employs motion-adaptive techniques
+with temporal reference frames for higher quality.
+@end table
+
+The default value is @code{default}.
+
+@item mode
+Specify the interlacing mode. It accepts one of the following values:
+
+@table @samp
+@item frame
+Send one frame for each frame. The output frame rate equals the input
+frame rate. This is the default.
+
+@item field
+Send one frame for each field. The output frame rate is double the
+input frame rate.
+@end table
+
+The default value is @code{frame}.
+
+@item deint
+Specify which frames to deinterlace. It accepts one of the following values:
+
+@table @samp
+@item all
+Deinterlace all frames. This is the default.
+
+@item interlaced
+Only deinterlace frames marked as interlaced; progressive frames are
+passed through unchanged.
+@end table
+
+The default value is @code{all}.
+@end table
+
+@subsection Examples
+
+@itemize
+
+@item
+Deinterlace an interlaced video using software decoding and the best
+available hardware deinterlacing method:
+@example
+ffmpeg -init_hw_device d3d12va=d3d12 -filter_hw_device d3d12 -i input.ts \
+       -vf "format=nv12,hwupload,deinterlace_d3d12=method=default,hwdownload,format=nv12" \
+       -c:v libx264 -crf 18 output.mp4
+@end example
+
+@item
+Deinterlace at field rate (double the frame rate) using bob method with
+hardware decoding (full d3d12 pipeline):
+@example
+ffmpeg -hwaccel d3d12va -hwaccel_output_format d3d12 -i input.ts \
+       -vf "deinterlace_d3d12=method=bob:mode=field" \
+       -c:v h264_d3d12va output.mp4
+@end example
+
+@item
+Deinterlace only interlaced frames, passing progressive frames through:
+@example
+ffmpeg -init_hw_device d3d12va=d3d12 -filter_hw_device d3d12 -i input.ts \
+       -vf "format=nv12,hwupload,deinterlace_d3d12=deint=interlaced,hwdownload,format=nv12" \
+       -c:v libx264 -crf 18 output.mp4
+@end example
+
+@end itemize
+
 @section dejudder
 
 Remove judder produced by partially interlaced telecined content.