avfilter: add xfade opencl filter

1 files changed, 97 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index cbff407189..d342e57472 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -21448,6 +21448,103 @@ Apply a strong blur of both luma and chroma parameters:
 @end example
 @end itemize
 
+@section xfade_opencl
+
+Cross fade two videos with custom transition effect by using OpenCL.
+
+It accepts the following options:
+
+@table @option
+@item transition
+Set one of possible transition effects.
+
+@table @option
+@item custom
+Select custom transition effect, the actual transition description
+will be picked from source and kernel options.
+
+@item fade
+@item wipeleft
+@item wiperight
+@item wipeup
+@item wipedown
+@item slideleft
+@item slideright
+@item slideup
+@item slidedown
+
+Default transition is fade.
+@end table
+
+@item source
+OpenCL program source file for custom transition.
+
+@item kernel
+Set name of kernel to use for custom transition from program source file.
+
+@item duration
+Set duration of video transition.
+
+@item offset
+Set time of start of transition relative to first video.
+@end table
+
+The program source file must contain a kernel function with the given name,
+which will be run once for each plane of the output.  Each run on a plane
+gets enqueued as a separate 2D global NDRange with one work-item for each
+pixel to be generated.  The global ID offset for each work-item is therefore
+the coordinates of a pixel in the destination image.
+
+The kernel function needs to take the following arguments:
+@itemize
+@item
+Destination image, @var{__write_only image2d_t}.
+
+This image will become the output; the kernel should write all of it.
+
+@item
+First Source image, @var{__read_only image2d_t}.
+Second Source image, @var{__read_only image2d_t}.
+
+These are the most recent images on each input.  The kernel may read from
+them to generate the output, but they can't be written to.
+
+@item
+Transition progress, @var{float}. This value is always between 0 and 1 inclusive.
+@end itemize
+
+Example programs:
+
+@itemize
+@item
+Apply dots curtain transition effect:
+@verbatim
+__kernel void blend_images(__write_only image2d_t dst,
+                           __read_only  image2d_t src1,
+                           __read_only  image2d_t src2,
+                           float progress)
+{
+    const sampler_t sampler = (CLK_NORMALIZED_COORDS_FALSE |
+                               CLK_FILTER_LINEAR);
+    int2  p = (int2)(get_global_id(0), get_global_id(1));
+    float2 rp = (float2)(get_global_id(0), get_global_id(1));
+    float2 dim = (float2)(get_image_dim(src1).x, get_image_dim(src1).y);
+    rp = rp / dim;
+
+    float2 dots = (float2)(20.0, 20.0);
+    float2 center = (float2)(0,0);
+    float2 unused;
+
+    float4 val1 = read_imagef(src1, sampler, p);
+    float4 val2 = read_imagef(src2, sampler, p);
+    bool next = distance(fract(rp * dots, &unused), (float2)(0.5, 0.5)) < (progress / distance(rp, center));
+
+    write_imagef(dst, p, next ? val1 : val2);
+}
+@end verbatim
+
+@end itemize
+
 @c man end OPENCL VIDEO FILTERS
 
 @chapter VAAPI Video Filters