diff --git a/3rdparty/carotene/src/resize.cpp b/3rdparty/carotene/src/resize.cpp
index 49205573cd..aa5b756c75 100644
--- a/3rdparty/carotene/src/resize.cpp
+++ b/3rdparty/carotene/src/resize.cpp
@@ -758,7 +758,7 @@ inline void resizeAreaRounding(const Size2D &ssize, const Size2D &dsize,
     }
     else if (channels == 3)
     {
-        if ((wr == 2.0f) && (wr == 2.0f))
+        if ((wr == 2.0f) && (hr == 2.0f))
         {
 #ifndef __ANDROID__
             size_t roiw16 = dsize.width >= 15 ? (dsize.width - 15) * 3 : 0;
diff --git a/cmake/OpenCVFindLibsGrfmt.cmake b/cmake/OpenCVFindLibsGrfmt.cmake
index 2e4e4afa9d..23a6ca6959 100644
--- a/cmake/OpenCVFindLibsGrfmt.cmake
+++ b/cmake/OpenCVFindLibsGrfmt.cmake
@@ -7,9 +7,17 @@ if(BUILD_ZLIB)
   ocv_clear_vars(ZLIB_FOUND)
 else()
   ocv_clear_internal_cache_vars(ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
+  if(ANDROID)
+    set(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+    set(CMAKE_FIND_LIBRARY_SUFFIXES .so)
+  endif()
   find_package(ZLIB "${MIN_VER_ZLIB}")
+  if(ANDROID)
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ${_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES})
+    unset(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES)
+  endif()
   if(ZLIB_FOUND AND ANDROID)
-    if(ZLIB_LIBRARIES MATCHES "/usr/(lib|lib32|lib64)/libz.so$")
+    if(ZLIB_LIBRARIES MATCHES "/usr/lib.*/libz.so$")
       set(ZLIB_LIBRARIES z)
     endif()
   endif()
diff --git a/cmake/OpenCVUtils.cmake b/cmake/OpenCVUtils.cmake
index a6ea60365a..f42ad0b231 100644
--- a/cmake/OpenCVUtils.cmake
+++ b/cmake/OpenCVUtils.cmake
@@ -564,7 +564,11 @@ macro(ocv_check_flag_support lang flag varname base_options)
   elseif("_${lang}_" MATCHES "_C_")
     set(_lang C)
   elseif("_${lang}_" MATCHES "_OBJCXX_")
-    set(_lang OBJCXX)
+    if(DEFINED CMAKE_OBJCXX_COMPILER)  # CMake 3.16+ and enable_language(OBJCXX) call are required
+      set(_lang OBJCXX)
+    else()
+      set(_lang CXX)
+    endif()
   else()
     set(_lang ${lang})
   endif()
diff --git a/doc/py_tutorials/py_setup/py_setup_in_ubuntu/py_setup_in_ubuntu.markdown b/doc/py_tutorials/py_setup/py_setup_in_ubuntu/py_setup_in_ubuntu.markdown
index f88ffe6793..8b99c5df92 100644
--- a/doc/py_tutorials/py_setup/py_setup_in_ubuntu/py_setup_in_ubuntu.markdown
+++ b/doc/py_tutorials/py_setup/py_setup_in_ubuntu/py_setup_in_ubuntu.markdown
@@ -22,10 +22,10 @@ Installing OpenCV-Python from Pre-built Binaries
 
 This method serves best when using just for programming and developing OpenCV applications.
 
-Install package [python-opencv](https://packages.ubuntu.com/trusty/python-opencv) with following command in terminal (as root user).
+Install package [python3-opencv](https://packages.ubuntu.com/focal/python3-opencv) with following command in terminal (as root user).
 
 ```
-$ sudo apt-get install python-opencv
+$ sudo apt-get install python3-opencv
 ```
 
 Open Python IDLE (or IPython) and type following codes in Python terminal.
diff --git a/doc/tutorials/imgproc/pyramids/pyramids.markdown b/doc/tutorials/imgproc/pyramids/pyramids.markdown
index adbd086cf0..82ef81e369 100644
--- a/doc/tutorials/imgproc/pyramids/pyramids.markdown
+++ b/doc/tutorials/imgproc/pyramids/pyramids.markdown
@@ -170,7 +170,7 @@ Our program exits if the user presses **ESC**. Besides, it has two options:
     We use the function **pyrDown()** with three arguments (similarly to **pyrUp()**):
             -   *src*: The current and destination image  (to be shown on screen, supposedly half the input
                 image)
-            -   *Size( tmp.cols/2, tmp.rows/2 )* : The destination size. Since we are upsampling,
+            -   *Size( tmp.cols/2, tmp.rows/2 )* : The destination size. Since we are downsampling,
                 **pyrDown()** expects half the size the input image (in this case *src*).
 
 @add_toggle_cpp
diff --git a/modules/calib3d/src/calibinit.cpp b/modules/calib3d/src/calibinit.cpp
index f9e0224542..320b9ae85d 100644
--- a/modules/calib3d/src/calibinit.cpp
+++ b/modules/calib3d/src/calibinit.cpp
@@ -2266,7 +2266,7 @@ bool findCirclesGrid( InputArray _image, Size patternSize,
         }
     }
 
-    if (!H.empty())  // undone rectification
+    if (!centers.empty() && !H.empty())  // undone rectification
     {
         Mat orgPointsMat;
         transform(centers, orgPointsMat, H.inv());
diff --git a/modules/calib3d/test/test_chesscorners.cpp b/modules/calib3d/test/test_chesscorners.cpp
index 822796fcfb..b4d0628c87 100644
--- a/modules/calib3d/test/test_chesscorners.cpp
+++ b/modules/calib3d/test/test_chesscorners.cpp
@@ -710,5 +710,45 @@ TEST(Calib3d_AsymmetricCirclesPatternDetector, regression_18713)
     }
 }
 
+TEST(Calib3d_AsymmetricCirclesPatternDetector, regression_19498)
+{
+    float pts_[121][2] = {
+        { 84.7462f, 404.504f }, { 49.1586f, 404.092f }, { 12.3362f, 403.434f }, { 102.542f, 386.214f }, { 67.6042f, 385.475f },
+        { 31.4982f, 384.569f }, { 141.231f, 377.856f }, { 332.834f, 370.745f }, { 85.7663f, 367.261f }, { 50.346f, 366.051f },
+        { 13.7726f, 364.663f }, { 371.746f, 362.011f }, { 68.8543f, 347.883f }, { 32.9334f, 346.263f }, { 331.926f, 343.291f },
+        { 351.535f, 338.112f }, { 51.7951f, 328.247f }, { 15.4613f, 326.095f }, { 311.719f, 319.578f }, { 330.947f, 313.708f },
+        { 256.706f, 307.584f }, { 34.6834f, 308.167f }, { 291.085f, 295.429f }, { 17.4316f, 287.824f }, { 252.928f, 277.92f },
+        { 270.19f, 270.93f }, { 288.473f, 263.484f }, { 216.401f, 260.94f }, { 232.195f, 253.656f }, { 266.757f, 237.708f },
+        { 211.323f, 229.005f }, { 227.592f, 220.498f }, { 154.749f, 188.52f }, { 222.52f, 184.906f }, { 133.85f, 163.968f },
+        { 200.024f, 158.05f }, { 147.485f, 153.643f }, { 161.967f, 142.633f }, { 177.396f, 131.059f }, { 125.909f, 128.116f },
+        { 139.817f, 116.333f }, { 91.8639f, 114.454f }, { 104.343f, 102.542f }, { 117.635f, 89.9116f }, { 70.9465f, 89.4619f },
+        { 82.8524f, 76.7862f }, { 131.738f, 76.4741f }, { 95.5012f, 63.3351f }, { 109.034f, 49.0424f }, { 314.886f, 374.711f },
+        { 351.735f, 366.489f }, { 279.113f, 357.05f }, { 313.371f, 348.131f }, { 260.123f, 335.271f }, { 276.346f, 330.325f },
+        { 293.588f, 325.133f }, { 240.86f, 313.143f }, { 273.436f, 301.667f }, { 206.762f, 296.574f }, { 309.877f, 288.796f },
+        { 187.46f, 274.319f }, { 201.521f, 267.804f }, { 248.973f, 245.918f }, { 181.644f, 244.655f }, { 196.025f, 237.045f },
+        { 148.41f, 229.131f }, { 161.604f, 221.215f }, { 175.455f, 212.873f }, { 244.748f, 211.459f }, { 128.661f, 206.109f },
+        { 190.217f, 204.108f }, { 141.346f, 197.568f }, { 205.876f, 194.781f }, { 168.937f, 178.948f }, { 121.006f, 173.714f },
+        { 183.998f, 168.806f }, { 88.9095f, 159.731f }, { 100.559f, 149.867f }, { 58.553f, 146.47f }, { 112.849f, 139.302f },
+        { 80.0968f, 125.74f }, { 39.24f, 123.671f }, { 154.582f, 103.85f }, { 59.7699f, 101.49f }, { 266.334f, 385.387f },
+        { 234.053f, 368.718f }, { 263.347f, 361.184f }, { 244.763f, 339.958f }, { 198.16f, 328.214f }, { 211.675f, 323.407f },
+        { 225.905f, 318.426f }, { 192.98f, 302.119f }, { 221.267f, 290.693f }, { 161.437f, 286.46f }, { 236.656f, 284.476f },
+        { 168.023f, 251.799f }, { 105.385f, 221.988f }, { 116.724f, 214.25f }, { 97.2959f, 191.81f }, { 108.89f, 183.05f },
+        { 77.9896f, 169.242f }, { 48.6763f, 156.088f }, { 68.9635f, 136.415f }, { 29.8484f, 133.886f }, { 49.1966f, 112.826f },
+        { 113.059f, 29.003f }, { 251.698f, 388.562f }, { 281.689f, 381.929f }, { 297.875f, 378.518f }, { 248.376f, 365.025f },
+        { 295.791f, 352.763f }, { 216.176f, 348.586f }, { 230.143f, 344.443f }, { 179.89f, 307.457f }, { 174.083f, 280.51f },
+        { 142.867f, 265.085f }, { 155.127f, 258.692f }, { 124.187f, 243.661f }, { 136.01f, 236.553f }, { 86.4651f, 200.13f },
+        { 67.5711f, 178.221f }
+    };
+
+    Mat candidates(121, 1, CV_32FC2, (void*)pts_);
+    Size patternSize(13, 8);
+
+    std::vector< Point2f > result;
+    bool res = false;
+
+    EXPECT_NO_THROW(res = findCirclesGrid(candidates, patternSize, result, CALIB_CB_SYMMETRIC_GRID, Ptr<FeatureDetector>()/*blobDetector=NULL*/));
+    EXPECT_FALSE(res);
+}
+
 }} // namespace
 /* End of file. */
diff --git a/modules/core/include/opencv2/core.hpp b/modules/core/include/opencv2/core.hpp
index 6ba209b397..48023844a9 100644
--- a/modules/core/include/opencv2/core.hpp
+++ b/modules/core/include/opencv2/core.hpp
@@ -50,7 +50,6 @@
 #endif
 
 #include "opencv2/core/cvdef.h"
-#include "opencv2/core/version.hpp"
 #include "opencv2/core/base.hpp"
 #include "opencv2/core/cvstd.hpp"
 #include "opencv2/core/traits.hpp"
diff --git a/modules/core/include/opencv2/core/cvdef.h b/modules/core/include/opencv2/core/cvdef.h
index d001ebc76c..cb12f19f90 100644
--- a/modules/core/include/opencv2/core/cvdef.h
+++ b/modules/core/include/opencv2/core/cvdef.h
@@ -45,6 +45,8 @@
 #ifndef OPENCV_CORE_CVDEF_H
 #define OPENCV_CORE_CVDEF_H
 
+#include "opencv2/core/version.hpp"
+
 //! @addtogroup core_utils
 //! @{
 
diff --git a/modules/core/include/opencv2/core/simd_intrinsics.hpp b/modules/core/include/opencv2/core/simd_intrinsics.hpp
index c50923f0ef..8fe7ee6b60 100644
--- a/modules/core/include/opencv2/core/simd_intrinsics.hpp
+++ b/modules/core/include/opencv2/core/simd_intrinsics.hpp
@@ -40,7 +40,6 @@ Notes:
 #endif
 
 #include "opencv2/core/cvdef.h"
-#include "opencv2/core/version.hpp"
 
 #ifdef OPENCV_SIMD_CONFIG_HEADER
 #include CVAUX_STR(OPENCV_SIMD_CONFIG_HEADER)
diff --git a/modules/core/src/hal_internal.cpp b/modules/core/src/hal_internal.cpp
index 60f96c0164..483281d1f7 100644
--- a/modules/core/src/hal_internal.cpp
+++ b/modules/core/src/hal_internal.cpp
@@ -42,6 +42,7 @@
 //
 //M*/
 
+#include "precomp.hpp"
 #include "hal_internal.hpp"
 
 #ifdef HAVE_LAPACK
diff --git a/modules/core/src/hal_internal.hpp b/modules/core/src/hal_internal.hpp
index 129a710145..c7a0d46de4 100644
--- a/modules/core/src/hal_internal.hpp
+++ b/modules/core/src/hal_internal.hpp
@@ -45,8 +45,6 @@
 #ifndef OPENCV_CORE_HAL_INTERNAL_HPP
 #define OPENCV_CORE_HAL_INTERNAL_HPP
 
-#include "precomp.hpp"
-
 #ifdef HAVE_LAPACK
 
 int lapack_LU32f(float* a, size_t a_step, int m, float* b, size_t b_step, int n, int* info);
diff --git a/modules/core/src/intel_gpu_gemm.inl.hpp b/modules/core/src/intel_gpu_gemm.inl.hpp
index 729b43f604..fbd567b949 100644
--- a/modules/core/src/intel_gpu_gemm.inl.hpp
+++ b/modules/core/src/intel_gpu_gemm.inl.hpp
@@ -25,7 +25,6 @@
 #ifdef HAVE_OPENCL
 
 #include <sstream>
-#include "precomp.hpp"
 #include "opencl_kernels_core.hpp"
 #include "opencv2/core/opencl/runtime/opencl_clamdblas.hpp"
 #include "opencv2/core/opencl/runtime/opencl_core.hpp"
diff --git a/modules/core/src/matrix_c.cpp b/modules/core/src/matrix_c.cpp
index 1c3e58857c..2fead4100c 100644
--- a/modules/core/src/matrix_c.cpp
+++ b/modules/core/src/matrix_c.cpp
@@ -1,6 +1,10 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html
+
+#include "precomp.hpp"
 #include "opencv2/core/mat.hpp"
 #include "opencv2/core/types_c.h"
-#include "precomp.hpp"
 
 // glue
 
diff --git a/modules/core/src/matrix_iterator.cpp b/modules/core/src/matrix_iterator.cpp
index aaa7f4aa01..ce7c191cbe 100644
--- a/modules/core/src/matrix_iterator.cpp
+++ b/modules/core/src/matrix_iterator.cpp
@@ -2,9 +2,8 @@
 // It is subject to the license terms in the LICENSE file found in the top-level directory
 // of this distribution and at http://opencv.org/license.html
 
-
-#include "opencv2/core/mat.hpp"
 #include "precomp.hpp"
+#include "opencv2/core/mat.hpp"
 
 namespace cv {
 
diff --git a/modules/core/src/matrix_operations.cpp b/modules/core/src/matrix_operations.cpp
index ac94ecee7d..b7068f195a 100644
--- a/modules/core/src/matrix_operations.cpp
+++ b/modules/core/src/matrix_operations.cpp
@@ -2,11 +2,10 @@
 // It is subject to the license terms in the LICENSE file found in the top-level directory
 // of this distribution and at http://opencv.org/license.html
 
-
+#include "precomp.hpp"
 #include "opencv2/core/mat.hpp"
 #include "opencv2/core/types_c.h"
 #include "opencl_kernels_core.hpp"
-#include "precomp.hpp"
 
 #undef HAVE_IPP
 #undef CV_IPP_RUN_FAST
diff --git a/modules/core/src/matrix_sparse.cpp b/modules/core/src/matrix_sparse.cpp
index 05d16d706e..21e7e91151 100644
--- a/modules/core/src/matrix_sparse.cpp
+++ b/modules/core/src/matrix_sparse.cpp
@@ -2,10 +2,9 @@
 // It is subject to the license terms in the LICENSE file found in the top-level directory
 // of this distribution and at http://opencv.org/license.html
 
-
+#include "precomp.hpp"
 #include "opencv2/core/mat.hpp"
 #include "opencv2/core/types_c.h"
-#include "precomp.hpp"
 
 namespace cv {
 
diff --git a/modules/core/src/matrix_wrap.cpp b/modules/core/src/matrix_wrap.cpp
index 68a674f6f1..b8afe61d6b 100644
--- a/modules/core/src/matrix_wrap.cpp
+++ b/modules/core/src/matrix_wrap.cpp
@@ -2,9 +2,8 @@
 // It is subject to the license terms in the LICENSE file found in the top-level directory
 // of this distribution and at http://opencv.org/license.html
 
-
-#include "opencv2/core/mat.hpp"
 #include "precomp.hpp"
+#include "opencv2/core/mat.hpp"
 
 namespace cv {
 
diff --git a/modules/dnn/src/darknet/darknet_io.cpp b/modules/dnn/src/darknet/darknet_io.cpp
index f6d71fd6d4..e3c978a8c0 100644
--- a/modules/dnn/src/darknet/darknet_io.cpp
+++ b/modules/dnn/src/darknet/darknet_io.cpp
@@ -241,6 +241,10 @@ namespace cv {
                     {
                         activation_param.type = "Sigmoid";
                     }
+                    else if (type == "tanh")
+                    {
+                        activation_param.type = "TanH";
+                    }
                     else
                     {
                         CV_Error(cv::Error::StsParseError, "Unsupported activation: " + type);
diff --git a/modules/dnn/src/layers/proposal_layer.cpp b/modules/dnn/src/layers/proposal_layer.cpp
index 4658e7b41f..62c4c7295f 100644
--- a/modules/dnn/src/layers/proposal_layer.cpp
+++ b/modules/dnn/src/layers/proposal_layer.cpp
@@ -54,11 +54,11 @@ public:
             for (int i = 0; i < ratios.size(); ++i)
             {
                 float ratio = ratios.get<float>(i);
+                float width = std::floor(baseSize / sqrt(ratio) + 0.5f);
+                float height = std::floor(width * ratio + 0.5f);
                 for (int j = 0; j < scales.size(); ++j)
                 {
                     float scale = scales.get<float>(j);
-                    float width = std::floor(baseSize / sqrt(ratio) + 0.5f);
-                    float height = std::floor(width * ratio + 0.5f);
                     widths.push_back(scale * width);
                     heights.push_back(scale * height);
                 }
diff --git a/modules/dnn/test/test_darknet_importer.cpp b/modules/dnn/test/test_darknet_importer.cpp
index ca880fd7c2..c6a5ab1c3e 100644
--- a/modules/dnn/test/test_darknet_importer.cpp
+++ b/modules/dnn/test/test_darknet_importer.cpp
@@ -735,6 +735,11 @@ TEST_P(Test_Darknet_layers, mish)
     testDarknetLayer("mish", true);
 }
 
+TEST_P(Test_Darknet_layers, tanh)
+{
+    testDarknetLayer("tanh");
+}
+
 TEST_P(Test_Darknet_layers, avgpool_softmax)
 {
     testDarknetLayer("avgpool_softmax");
diff --git a/modules/highgui/CMakeLists.txt b/modules/highgui/CMakeLists.txt
index d7a3c220d1..7a546616a4 100644
--- a/modules/highgui/CMakeLists.txt
+++ b/modules/highgui/CMakeLists.txt
@@ -148,7 +148,7 @@ ocv_create_module(${HIGHGUI_LIBRARIES})
 
 macro(ocv_highgui_configure_target)
 if(APPLE)
-  add_apple_compiler_options(the_module)
+  add_apple_compiler_options(${the_module})
 endif()
 
 if(MSVC)
diff --git a/modules/imgcodecs/CMakeLists.txt b/modules/imgcodecs/CMakeLists.txt
index 7280778686..24f89e6e38 100644
--- a/modules/imgcodecs/CMakeLists.txt
+++ b/modules/imgcodecs/CMakeLists.txt
@@ -149,7 +149,7 @@ ocv_create_module(${GRFMT_LIBS} ${IMGCODECS_LIBRARIES})
 
 macro(ocv_imgcodecs_configure_target)
 if(APPLE)
-  add_apple_compiler_options(the_module)
+  add_apple_compiler_options(${the_module})
 endif()
 
 if(MSVC)
@@ -167,4 +167,8 @@ ocv_add_accuracy_tests()
 if(TARGET opencv_test_imgcodecs AND HAVE_JASPER AND "$ENV{OPENCV_IO_ENABLE_JASPER}")
   ocv_target_compile_definitions(opencv_test_imgcodecs PRIVATE OPENCV_IMGCODECS_ENABLE_JASPER_TESTS=1)
 endif()
+if(TARGET opencv_test_imgcodecs AND HAVE_PNG AND NOT (PNG_VERSION VERSION_LESS "1.6.31"))
+  # details: https://github.com/glennrp/libpng/commit/68cb0aaee3de6371b81a4613476d9b33e43e95b1
+  ocv_target_compile_definitions(opencv_test_imgcodecs PRIVATE OPENCV_IMGCODECS_PNG_WITH_EXIF=1)
+endif()
 ocv_add_perf_tests()
diff --git a/modules/imgcodecs/test/test_png.cpp b/modules/imgcodecs/test/test_png.cpp
index 74920ee9ae..f71fabc7e4 100644
--- a/modules/imgcodecs/test/test_png.cpp
+++ b/modules/imgcodecs/test/test_png.cpp
@@ -7,12 +7,6 @@ namespace opencv_test { namespace {
 
 #ifdef HAVE_PNG
 
-#ifdef HAVE_LIBPNG_PNG_H
-#include <libpng/png.h>
-#else
-#include <png.h>
-#endif
-
 TEST(Imgcodecs_Png, write_big)
 {
     const string root = cvtest::TS::ptr()->get_data_path();
@@ -99,7 +93,6 @@ TEST(Imgcodecs_Png, read_color_palette_with_alpha)
     EXPECT_EQ(img.at<Vec3b>(0, 1), Vec3b(0, 0, 255));
 }
 
-#ifdef PNG_eXIf_SUPPORTED
 /**
  * Test for check whether reading exif orientation tag was processed successfully or not
  * The test info is the set of 8 images named testExifRotate_{1 to 8}.png
@@ -144,7 +137,11 @@ TEST(Imgcodecs_Png, read_color_palette_with_alpha)
 typedef testing::TestWithParam<string> Imgcodecs_PNG_Exif;
 
 // Solution to issue 16579: PNG read doesn't support Exif orientation data
+#ifdef OPENCV_IMGCODECS_PNG_WITH_EXIF
 TEST_P(Imgcodecs_PNG_Exif, exif_orientation)
+#else
+TEST_P(Imgcodecs_PNG_Exif, DISABLED_exif_orientation)
+#endif
 {
     const string root = cvtest::TS::ptr()->get_data_path();
     const string filename = root + GetParam();
@@ -188,7 +185,6 @@ const string exif_files[] =
 
 INSTANTIATE_TEST_CASE_P(ExifFiles, Imgcodecs_PNG_Exif,
     testing::ValuesIn(exif_files));
-#endif // PNG_eXIf_SUPPORTED
 
 #endif // HAVE_PNG
 
diff --git a/modules/video/src/lkpyramid.cpp b/modules/video/src/lkpyramid.cpp
index 29307053f3..8467035dbf 100644
--- a/modules/video/src/lkpyramid.cpp
+++ b/modules/video/src/lkpyramid.cpp
@@ -865,6 +865,8 @@ namespace
                           OutputArray status,
                           OutputArray err = cv::noArray()) CV_OVERRIDE;
 
+        virtual String getDefaultName() const CV_OVERRIDE { return "SparseOpticalFlow.SparsePyrLKOpticalFlow"; }
+
     private:
 #ifdef HAVE_OPENCL
         bool checkParam()
@@ -934,7 +936,8 @@ namespace
             {
                 if (!lkSparse_run(prevPyr[level], nextPyr[level], prevPts,
                                   nextPts, status, err,
-                                  prevPts.cols, level))
+                                  static_cast<int>(prevPts.total()),
+                                  level))
                     return false;
             }
             return true;
diff --git a/modules/video/src/optflowgf.cpp b/modules/video/src/optflowgf.cpp
index 83ad47fc0e..2b164b62d3 100644
--- a/modules/video/src/optflowgf.cpp
+++ b/modules/video/src/optflowgf.cpp
@@ -618,6 +618,8 @@ public:
 
     virtual void calc(InputArray I0, InputArray I1, InputOutputArray flow) CV_OVERRIDE;
 
+    virtual String getDefaultName() const CV_OVERRIDE { return "DenseOpticalFlow.FarnebackOpticalFlow"; }
+
 private:
     int numLevels_;
     double pyrScale_;
diff --git a/samples/cpp/tutorial_code/calib3d/camera_calibration/camera_calibration.cpp b/samples/cpp/tutorial_code/calib3d/camera_calibration/camera_calibration.cpp
index 2d8b1ddac4..07ffbd5f19 100644
--- a/samples/cpp/tutorial_code/calib3d/camera_calibration/camera_calibration.cpp
+++ b/samples/cpp/tutorial_code/calib3d/camera_calibration/camera_calibration.cpp
@@ -444,7 +444,7 @@ int main(int argc, char* argv[])
 
     // -----------------------Show the undistorted image for the image list ------------------------
     //! [show_results]
-    if( s.inputType == Settings::IMAGE_LIST && s.showUndistorsed )
+    if( s.inputType == Settings::IMAGE_LIST && s.showUndistorsed && !cameraMatrix.empty())
     {
         Mat view, rview, map1, map2;
 
diff --git a/samples/dnn/tf_text_graph_common.py b/samples/dnn/tf_text_graph_common.py
index ea24898873..c82053b4fb 100644
--- a/samples/dnn/tf_text_graph_common.py
+++ b/samples/dnn/tf_text_graph_common.py
@@ -270,7 +270,11 @@ def removeIdentity(graph_def):
     identities = {}
     for node in graph_def.node:
         if node.op == 'Identity' or node.op == 'IdentityN':
-            identities[node.name] = node.input[0]
+            inp = node.input[0]
+            if inp in identities:
+                identities[node.name] = identities[inp]
+            else:
+                identities[node.name] = inp
             graph_def.node.remove(node)
 
     for node in graph_def.node: