avfilter: add chromakey_cuda filter

GSoC'22

libavfilter/vf_chromakey_cuda.cu:the CUDA kernel for the filter
libavfilter/vf_chromakey_cuda.c: the C side that calls the kernel and gets user input
libavfilter/allfilters.c: added the filter to it
libavfilter/Makefile: added the filter to it
cuda/cuda_runtime.h: added two math CUDA functions that are used in the filter

Signed-off-by: Timo Rothenpieler <timo@rothenpieler.org>

5 files changed, 676 insertions, 1 deletions

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 139f7cb751..30cc329fb6 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -210,6 +210,8 @@ OBJS-$(CONFIG_CAS_FILTER)                    += vf_cas.o
 OBJS-$(CONFIG_CHROMABER_VULKAN_FILTER)       += vf_chromaber_vulkan.o vulkan.o vulkan_filter.o
 OBJS-$(CONFIG_CHROMAHOLD_FILTER)             += vf_chromakey.o
 OBJS-$(CONFIG_CHROMAKEY_FILTER)              += vf_chromakey.o
+OBJS-$(CONFIG_CHROMAKEY_CUDA_FILTER)         += vf_chromakey_cuda.o vf_chromakey_cuda.ptx.o
+
 OBJS-$(CONFIG_CHROMANR_FILTER)               += vf_chromanr.o
 OBJS-$(CONFIG_CHROMASHIFT_FILTER)            += vf_chromashift.o
 OBJS-$(CONFIG_CIESCOPE_FILTER)               += vf_ciescope.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 3018850b4b..5ebacfde27 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -195,6 +195,7 @@ extern const AVFilter ff_vf_cas;
 extern const AVFilter ff_vf_chromaber_vulkan;
 extern const AVFilter ff_vf_chromahold;
 extern const AVFilter ff_vf_chromakey;
+extern const AVFilter ff_vf_chromakey_cuda;
 extern const AVFilter ff_vf_chromanr;
 extern const AVFilter ff_vf_chromashift;
 extern const AVFilter ff_vf_ciescope;
diff --git a/libavfilter/version.h b/libavfilter/version.h
index 37f03b44a6..2f4f4c6c21 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFILTER_VERSION_MINOR  42
+#define LIBAVFILTER_VERSION_MINOR  43
 #define LIBAVFILTER_VERSION_MICRO 100
 
 
diff --git a/libavfilter/vf_chromakey_cuda.c b/libavfilter/vf_chromakey_cuda.c
new file mode 100644
index 0000000000..113484279c
--- /dev/null
+++ b/libavfilter/vf_chromakey_cuda.c
@@ -0,0 +1,498 @@
+/*
+ * Copyright (c) 2022 Mohamed Khaled <Mohamed_Khaled_Kamal@outlook.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <float.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "libavutil/avstring.h"
+#include "libavutil/common.h"
+#include "libavutil/hwcontext.h"
+#include "libavutil/hwcontext_cuda_internal.h"
+#include "libavutil/cuda_check.h"
+#include "libavutil/internal.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "cuda/load_helper.h"
+
+static const enum AVPixelFormat supported_formats[] = {
+    AV_PIX_FMT_YUV420P,
+    AV_PIX_FMT_NV12,
+    AV_PIX_FMT_YUVA420P
+};
+
+#define DIV_UP(a, b) (((a) + (b)-1) / (b))
+#define BLOCKX 32
+#define BLOCKY 16
+#define CHECK_CU(x) FF_CUDA_CHECK_DL(ctx, s->hwctx->internal->cuda_dl, x)
+
+typedef struct ChromakeyCUDAContext {
+    const AVClass *class;
+
+    AVCUDADeviceContext *hwctx;
+
+    enum AVPixelFormat in_fmt, out_fmt;
+    const AVPixFmtDescriptor *in_desc, *out_desc;
+    int in_planes, out_planes;
+    int in_plane_depths[4];
+    int in_plane_channels[4];
+
+    uint8_t chromakey_rgba[4];
+    uint16_t chromakey_uv[2];
+    int is_yuv;
+    float similarity;
+    float blend;
+
+    AVBufferRef *frames_ctx;
+    AVFrame *frame;
+    AVFrame *tmp_frame;
+
+    CUcontext cu_ctx;
+    CUmodule cu_module;
+    CUfunction cu_func;
+    CUfunction cu_func_uv;
+    CUstream cu_stream;
+} ChromakeyCUDAContext;
+
+static av_cold int cudachromakey_init(AVFilterContext *ctx)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+
+    s->frame = av_frame_alloc();
+    if (!s->frame)
+        return AVERROR(ENOMEM);
+
+    s->tmp_frame = av_frame_alloc();
+    if (!s->tmp_frame)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static av_cold void cudachromakey_uninit(AVFilterContext *ctx)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+
+    if (s->hwctx && s->cu_module)
+    {
+        CudaFunctions *cu = s->hwctx->internal->cuda_dl;
+        CUcontext context;
+
+        CHECK_CU(cu->cuCtxPushCurrent(s->hwctx->cuda_ctx));
+        CHECK_CU(cu->cuModuleUnload(s->cu_module));
+        s->cu_module = NULL;
+        CHECK_CU(cu->cuCtxPopCurrent(&context));
+    }
+
+    av_frame_free(&s->frame);
+    av_buffer_unref(&s->frames_ctx);
+    av_frame_free(&s->tmp_frame);
+}
+
+static av_cold int init_hwframe_ctx(ChromakeyCUDAContext *s, AVBufferRef *device_ctx, int width, int height)
+{
+    AVBufferRef *out_ref = NULL;
+    AVHWFramesContext *out_ctx;
+    int ret;
+
+    out_ref = av_hwframe_ctx_alloc(device_ctx);
+    if (!out_ref)
+        return AVERROR(ENOMEM);
+    out_ctx = (AVHWFramesContext *)out_ref->data;
+
+    out_ctx->format     = AV_PIX_FMT_CUDA;
+    out_ctx->sw_format  = s->out_fmt;
+    out_ctx->width      = width;
+    out_ctx->height     = height;
+
+    ret = av_hwframe_ctx_init(out_ref);
+    if (ret < 0)
+        goto fail;
+
+    av_frame_unref(s->frame);
+    ret = av_hwframe_get_buffer(out_ref, s->frame, 0);
+    if (ret < 0)
+        goto fail;
+
+    av_buffer_unref(&s->frames_ctx);
+    s->frames_ctx = out_ref;
+
+    return 0;
+fail:
+    av_buffer_unref(&out_ref);
+    return ret;
+}
+
+static int format_is_supported(enum AVPixelFormat fmt)
+{
+    int i;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(supported_formats); i++)
+        if (supported_formats[i] == fmt)
+            return 1;
+    return 0;
+}
+
+static av_cold void set_format_info(AVFilterContext *ctx, enum AVPixelFormat in_format, enum AVPixelFormat out_format)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+    int i, p, d;
+
+    s->in_fmt       = in_format;
+    s->out_fmt      = out_format;
+
+    s->in_desc      = av_pix_fmt_desc_get(s->in_fmt);
+    s->out_desc     = av_pix_fmt_desc_get(s->out_fmt);
+    s->in_planes    = av_pix_fmt_count_planes(s->in_fmt);
+    s->out_planes   = av_pix_fmt_count_planes(s->out_fmt);
+
+    // find maximum step of each component of each plane
+    // For our subset of formats, this should accurately tell us how many channels CUDA needs
+    // i.e. 1 for Y plane, 2 for UV plane of NV12, 4 for single plane of RGB0 formats
+
+    for (i = 0; i < s->in_desc->nb_components; i++)
+    {
+        d = (s->in_desc->comp[i].depth + 7) / 8;
+        p = s->in_desc->comp[i].plane;
+        s->in_plane_channels[p] = FFMAX(s->in_plane_channels[p], s->in_desc->comp[i].step / d);
+
+        s->in_plane_depths[p]   = s->in_desc->comp[i].depth;
+    }
+}
+
+static av_cold int init_processing_chain(AVFilterContext *ctx, int width, int height)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+    AVHWFramesContext *in_frames_ctx;
+    int ret;
+
+    /* check that we have a hw context */
+    if (!ctx->inputs[0]->hw_frames_ctx)
+    {
+        av_log(ctx, AV_LOG_ERROR, "No hw context provided on input\n");
+        return AVERROR(EINVAL);
+    }
+    in_frames_ctx = (AVHWFramesContext *)ctx->inputs[0]->hw_frames_ctx->data;
+
+    if (!format_is_supported(in_frames_ctx->sw_format))
+    {
+        av_log(ctx, AV_LOG_ERROR, "Unsupported format: %s\n", av_get_pix_fmt_name(in_frames_ctx->sw_format));
+        return AVERROR(ENOSYS);
+    }
+
+    set_format_info(ctx, in_frames_ctx->sw_format, AV_PIX_FMT_YUVA420P);
+
+    ret = init_hwframe_ctx(s, in_frames_ctx->device_ref, width, height);
+    if (ret < 0)
+        return ret;
+
+    ctx->outputs[0]->hw_frames_ctx = av_buffer_ref(s->frames_ctx);
+    if (!ctx->outputs[0]->hw_frames_ctx)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static av_cold int cudachromakey_load_functions(AVFilterContext *ctx)
+{
+    ChromakeyCUDAContext *s   = ctx->priv;
+    CUcontext context, cuda_ctx = s->hwctx->cuda_ctx;
+    CudaFunctions *cu = s->hwctx->internal->cuda_dl;
+    int ret;
+
+    extern const unsigned char ff_vf_chromakey_cuda_ptx_data[];
+    extern const unsigned int ff_vf_chromakey_cuda_ptx_len;
+
+    ret = CHECK_CU(cu->cuCtxPushCurrent(cuda_ctx));
+    if (ret < 0)
+        return ret;
+
+    ret = ff_cuda_load_module(ctx, s->hwctx, &s->cu_module,
+                              ff_vf_chromakey_cuda_ptx_data, ff_vf_chromakey_cuda_ptx_len);
+    if (ret < 0)
+        goto fail;
+
+    ret = CHECK_CU(cu->cuModuleGetFunction(&s->cu_func, s->cu_module, "Process_uchar"));
+    if (ret < 0)
+    {
+        av_log(ctx, AV_LOG_FATAL, "Failed loading Process_uchar\n");
+        goto fail;
+    }
+
+    ret = CHECK_CU(cu->cuModuleGetFunction(&s->cu_func_uv, s->cu_module, "Process_uchar2"));
+    if (ret < 0)
+    {
+        av_log(ctx, AV_LOG_FATAL, "Failed loading Process_uchar2\n");
+        goto fail;
+    }
+
+fail:
+    CHECK_CU(cu->cuCtxPopCurrent(&context));
+
+    return ret;
+}
+
+#define FIXNUM(x) lrint((x) * (1 << 10))
+#define RGB_TO_U(rgb) (((-FIXNUM(0.16874) * rgb[0] - FIXNUM(0.33126) * rgb[1] + FIXNUM(0.50000) * rgb[2] + (1 << 9) - 1) >> 10) + 128)
+#define RGB_TO_V(rgb) (((FIXNUM(0.50000) * rgb[0] - FIXNUM(0.41869) * rgb[1] - FIXNUM(0.08131) * rgb[2] + (1 << 9) - 1) >> 10) + 128)
+
+static av_cold int cudachromakey_config_props(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+    ChromakeyCUDAContext *s = ctx->priv;
+    AVHWFramesContext *frames_ctx = (AVHWFramesContext *)inlink->hw_frames_ctx->data;
+    AVCUDADeviceContext *device_hwctx = frames_ctx->device_ctx->hwctx;
+    int ret;
+
+    s->hwctx = device_hwctx;
+    s->cu_stream = s->hwctx->stream;
+
+    if (s->is_yuv) {
+        s->chromakey_uv[0] = s->chromakey_rgba[1];
+        s->chromakey_uv[1] = s->chromakey_rgba[2];
+    } else {
+        s->chromakey_uv[0] = RGB_TO_U(s->chromakey_rgba);
+        s->chromakey_uv[1] = RGB_TO_V(s->chromakey_rgba);
+    }
+
+    ret = init_processing_chain(ctx, inlink->w, inlink->h);
+    if (ret < 0)
+        return ret;
+
+    outlink->sample_aspect_ratio = inlink->sample_aspect_ratio;
+
+    ret = cudachromakey_load_functions(ctx);
+    if (ret < 0)
+        return ret;
+
+    return 0;
+}
+
+static int call_cuda_kernel(AVFilterContext *ctx, CUfunction func,
+                            CUtexObject src_tex[3], AVFrame *out_frame,
+                            int width, int height, int pitch,
+                            int width_uv, int height_uv, int pitch_uv,
+                            float u_key, float v_key, float similarity,
+                            float blend)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+    CudaFunctions *cu = s->hwctx->internal->cuda_dl;
+
+    CUdeviceptr dst_devptr[4] = {
+        (CUdeviceptr)out_frame->data[0], (CUdeviceptr)out_frame->data[1],
+        (CUdeviceptr)out_frame->data[2], (CUdeviceptr)out_frame->data[3]
+    };
+
+    void *args_uchar[] = {
+        &src_tex[0], &src_tex[1], &src_tex[2],
+        &dst_devptr[0], &dst_devptr[1], &dst_devptr[2], &dst_devptr[3],
+        &width, &height, &pitch,
+        &width_uv, &height_uv, &pitch_uv,
+        &u_key, &v_key, &similarity, &blend
+    };
+
+    return CHECK_CU(cu->cuLaunchKernel(func,
+                                       DIV_UP(width, BLOCKX), DIV_UP(height, BLOCKY), 1,
+                                       BLOCKX, BLOCKY, 1, 0, s->cu_stream, args_uchar, NULL));
+}
+
+static int cudachromakey_process_internal(AVFilterContext *ctx,
+                                          AVFrame *out, AVFrame *in)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+    CudaFunctions *cu       = s->hwctx->internal->cuda_dl;
+    CUcontext context, cuda_ctx = s->hwctx->cuda_ctx;
+    int i, ret;
+
+    CUtexObject tex[3] = {0, 0, 0};
+
+    ret = CHECK_CU(cu->cuCtxPushCurrent(cuda_ctx));
+    if (ret < 0)
+        return ret;
+
+    for (i = 0; i < s->in_planes; i++)
+    {
+        CUDA_TEXTURE_DESC tex_desc = {
+            .filterMode = CU_TR_FILTER_MODE_LINEAR,
+            .flags = 0, // CU_TRSF_READ_AS_INTEGER to get raw ints instead of normalized floats from tex2D
+        };
+
+        CUDA_RESOURCE_DESC res_desc = {
+            .resType = CU_RESOURCE_TYPE_PITCH2D,
+            .res.pitch2D.format   = CU_AD_FORMAT_UNSIGNED_INT8,
+            .res.pitch2D.numChannels = s->in_plane_channels[i],
+            .res.pitch2D.pitchInBytes = in->linesize[i],
+            .res.pitch2D.devPtr = (CUdeviceptr)in->data[i],
+        };
+
+        if (i == 1 || i == 2)
+        {
+            res_desc.res.pitch2D.width  = AV_CEIL_RSHIFT(in->width, s->in_desc->log2_chroma_w);
+            res_desc.res.pitch2D.height = AV_CEIL_RSHIFT(in->height, s->in_desc->log2_chroma_h);
+        }
+        else
+        {
+            res_desc.res.pitch2D.width  = in->width;
+            res_desc.res.pitch2D.height = in->height;
+        }
+
+        ret = CHECK_CU(cu->cuTexObjectCreate(&tex[i], &res_desc, &tex_desc, NULL));
+        if (ret < 0)
+            goto exit;
+    }
+
+    ret = call_cuda_kernel(ctx, (s->in_plane_channels[1] > 1) ? s->cu_func_uv : s->cu_func,
+                           tex, out,
+                           out->width, out->height, out->linesize[0],
+                           AV_CEIL_RSHIFT(out->width, s->out_desc->log2_chroma_w),
+                           AV_CEIL_RSHIFT(out->height, s->out_desc->log2_chroma_h),
+                           out->linesize[1],
+                           s->chromakey_uv[0], s->chromakey_uv[1],
+                           s->similarity, s->blend);
+    if (ret < 0)
+        goto exit;
+
+exit:
+    for (i = 0; i < s->in_planes; i++)
+        if (tex[i])
+            CHECK_CU(cu->cuTexObjectDestroy(tex[i]));
+
+    CHECK_CU(cu->cuCtxPopCurrent(&context));
+
+    return ret;
+}
+
+static int cudachromakey_process(AVFilterContext *ctx, AVFrame *out, AVFrame *in)
+{
+    ChromakeyCUDAContext *s = ctx->priv;
+    AVFrame *src = in;
+    int ret;
+
+    ret = cudachromakey_process_internal(ctx, s->frame, src);
+    if (ret < 0)
+        return ret;
+
+    src = s->frame;
+    ret = av_hwframe_get_buffer(src->hw_frames_ctx, s->tmp_frame, 0);
+    if (ret < 0)
+        return ret;
+
+    av_frame_move_ref(out, s->frame);
+    av_frame_move_ref(s->frame, s->tmp_frame);
+
+    ret = av_frame_copy_props(out, in);
+    if (ret < 0)
+        return ret;
+
+    return 0;
+}
+
+static int cudachromakey_filter_frame(AVFilterLink *link, AVFrame *in)
+{
+    AVFilterContext *ctx    = link->dst;
+    ChromakeyCUDAContext *s = ctx->priv;
+    AVFilterLink *outlink   = ctx->outputs[0];
+    CudaFunctions *cu = s->hwctx->internal->cuda_dl;
+
+    AVFrame *out   = NULL;
+    CUcontext context;
+    int ret = 0;
+
+    out = av_frame_alloc();
+    if (!out)
+    {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+
+    ret = CHECK_CU(cu->cuCtxPushCurrent(s->hwctx->cuda_ctx));
+    if (ret < 0)
+        goto fail;
+
+    ret = cudachromakey_process(ctx, out, in);
+
+    CHECK_CU(cu->cuCtxPopCurrent(&context));
+    if (ret < 0)
+        goto fail;
+
+    av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+fail:
+    av_frame_free(&in);
+    av_frame_free(&out);
+    return ret;
+}
+
+#define OFFSET(x) offsetof(ChromakeyCUDAContext, x)
+#define FLAGS (AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM)
+static const AVOption options[] = {
+    {"color", "set the chromakey key color", OFFSET(chromakey_rgba), AV_OPT_TYPE_COLOR, {.str = "black"}, 0, 0, FLAGS},
+    {"similarity", "set the chromakey similarity value", OFFSET(similarity), AV_OPT_TYPE_FLOAT, {.dbl = 0.01}, 0.01, 1.0, FLAGS},
+    {"blend", "set the chromakey key blend value", OFFSET(blend), AV_OPT_TYPE_FLOAT, {.dbl = 0.0}, 0.0, 1.0, FLAGS},
+    {"yuv", "color parameter is in yuv instead of rgb", OFFSET(is_yuv), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, FLAGS},
+    {NULL},
+};
+
+static const AVClass cudachromakey_class = {
+    .class_name = "cudachromakey",
+    .item_name = av_default_item_name,
+    .option = options,
+    .version = LIBAVUTIL_VERSION_INT,
+};
+
+static const AVFilterPad cudachromakey_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = cudachromakey_filter_frame,
+    },
+};
+
+static const AVFilterPad cudachromakey_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .config_props = cudachromakey_config_props,
+    },
+};
+
+const AVFilter ff_vf_chromakey_cuda = {
+    .name = "chromakey_cuda",
+    .description = NULL_IF_CONFIG_SMALL("GPU accelerated chromakey filter"),
+
+    .init = cudachromakey_init,
+    .uninit = cudachromakey_uninit,
+
+    .priv_size = sizeof(ChromakeyCUDAContext),
+    .priv_class = &cudachromakey_class,
+
+    FILTER_INPUTS(cudachromakey_inputs),
+    FILTER_OUTPUTS(cudachromakey_outputs),
+
+    FILTER_SINGLE_PIXFMT(AV_PIX_FMT_CUDA),
+
+    .flags_internal = FF_FILTER_FLAG_HWFRAME_AWARE,
+};
diff --git a/libavfilter/vf_chromakey_cuda.cu b/libavfilter/vf_chromakey_cuda.cu
new file mode 100644
index 0000000000..25a10786ab
--- /dev/null
+++ b/libavfilter/vf_chromakey_cuda.cu
@@ -0,0 +1,174 @@
+/*
+ * Copyright (c) 2022 Mohamed Khaled <Mohamed_Khaled_Kamal@outlook.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "cuda/vector_helpers.cuh"
+
+extern "C"
+{
+
+/**
+ * @brief function contains the main logic of chroma keying, and changes the alpahc channel with the suitable value
+ *
+ * @param src_tex           texture U or texture UV , decided based on the passed is_uchar2 flag
+ * @param src_tex_V         texture V , used only if is_uchar2 flag is false
+ * @param dst_A             alpha channel destination
+ * @param width_uv          width of uv channels
+ * @param height_uv         height of uv channels
+ * @param width             width of alpha channel
+ * @param height            height of alpha channel
+ * @param pitch             pitch of alpha channel
+ * @param x                 current x coordinate of pixel
+ * @param y                 current y coordinate of pixel
+ * @param chromakey_uv      uv values for chroma keying
+ * @param similarity        similarity of keying
+ * @param blend             blend of keying
+ */
+__device__ static inline void change_alpha_channel(
+    cudaTextureObject_t src_tex, cudaTextureObject_t src_tex_V, uchar *dst_A,
+    int width_uv, int height_uv,
+    int width, int height, int pitch,
+    int x, int y,
+    float2 chromakey_uv, float similarity, float blend)
+{
+    int window_size = 3;
+    int start_r = x - window_size / 2;
+    int start_c = y - window_size / 2;
+    int resize_ratio = width / width_uv;
+    int counter = 0;
+    float diff = 0.0f;
+    float du, dv;
+    uchar alpha_value;
+
+    // loop over the eight neighbourhood of the current pixel(x,y)
+    for (uchar i = 0; i < window_size; i++)
+    {
+        for (uchar j = 0; j < window_size; j++)
+        {
+            float u_value, v_value;
+            int r = start_r + i;
+            int c = start_c + j;
+
+            if (r < 0 || r >= width_uv || c < 0 || c >= height_uv)
+                continue;
+
+            if (!src_tex_V) {
+                float2 temp_uv = tex2D<float2>(src_tex, r, c);
+                u_value = temp_uv.x;
+                v_value = temp_uv.y;
+            } else {
+                u_value = tex2D<float>(src_tex, r, c);
+                v_value = tex2D<float>(src_tex_V, r, c);
+            }
+
+            du = (u_value * 255.0f) - chromakey_uv.x;
+            dv = (v_value * 255.0f) - chromakey_uv.y;
+            diff += sqrtf((du * du + dv * dv) / (255.0f * 255.0f * 2.f));
+
+            counter++;
+        }
+    }
+
+    if (counter > 0)
+        diff = diff / counter;
+    else
+        diff /= 9.0f;
+
+    if (blend>0.0001f)
+        alpha_value = __saturatef((diff - similarity) / blend) * 255;
+    else
+        alpha_value = (diff < similarity) ? 0 : 255;
+
+    //write the value in the alpha channel with regarding the ratio of (alpha_size : uv_size)
+    for (uchar k = 0; k < resize_ratio; k++)
+    {
+        for (uchar l = 0; l < resize_ratio; l++)
+        {
+            int x_resize = x * resize_ratio + k;
+            int y_resize = y * resize_ratio + l;
+            int a_channel_resize = y_resize * pitch + x_resize;
+
+            if (y_resize >= height || x_resize >= width)
+                continue;
+
+            dst_A[a_channel_resize] = alpha_value;
+        }
+    }
+}
+
+__global__ void Process_uchar(
+    cudaTextureObject_t src_tex_Y, cudaTextureObject_t src_tex_U, cudaTextureObject_t src_tex_V,
+    uchar *dst_Y, uchar *dst_U, uchar *dst_V, uchar *dst_A,
+    int width, int height, int pitch,
+    int width_uv, int height_uv, int pitch_uv,
+    float u_key, float v_key, float similarity, float blend)
+{
+    int x = blockIdx.x * blockDim.x + threadIdx.x;
+    int y = blockIdx.y * blockDim.y + threadIdx.y;
+
+    if (y >= height || x >= width)
+        return;
+
+    dst_Y[y * pitch + x] = tex2D<float>(src_tex_Y, x, y)*255;
+
+    if (y >= height_uv || x >= width_uv)
+        return;
+
+    int uv_index = y * pitch_uv + x;
+    dst_U[uv_index] = tex2D<float>(src_tex_U, x, y) * 255;
+    dst_V[uv_index] = tex2D<float>(src_tex_V, x, y) * 255;
+
+    change_alpha_channel(src_tex_U, src_tex_V, dst_A,
+                         width_uv, height_uv,
+                         width, height, pitch,
+                         x, y,
+                         make_float2(u_key, v_key), similarity, blend);
+}
+
+__global__ void Process_uchar2(
+    cudaTextureObject_t src_tex_Y, cudaTextureObject_t src_tex_UV, cudaTextureObject_t unused1,
+    uchar *dst_Y, uchar *dst_U, uchar *dst_V, uchar *dst_A,
+    int width, int height, int pitch,
+    int width_uv, int height_uv,int pitch_uv,
+    float u_key, float v_key, float similarity, float blend)
+{
+    int x = blockIdx.x * blockDim.x + threadIdx.x;  // x coordinate of current pixel
+    int y = blockIdx.y * blockDim.y + threadIdx.y;  // y coordinate of current pixel
+
+    if (y >= height || x >= width)
+        return;
+
+    dst_Y[y * pitch + x] = tex2D<float>(src_tex_Y, x, y) * 255;
+
+    if (y >= height_uv || x >= width_uv)
+        return;
+
+    int uv_index = y * pitch_uv + x;
+    float2 uv_temp = tex2D<float2>(src_tex_UV, x, y);
+    dst_U[uv_index] = uv_temp.x * 255;
+    dst_V[uv_index] = uv_temp.y * 255;
+
+    change_alpha_channel(src_tex_UV, (cudaTextureObject_t)nullptr,
+                         dst_A, width_uv, height_uv,
+                         width, height, pitch,
+                         x, y,
+                         make_float2(u_key, v_key), similarity, blend);
+}
+
+}