diff --git a/modules/dnn/src/layers/detection_output_layer.cpp b/modules/dnn/src/layers/detection_output_layer.cpp
index de97c873af..77d86d5652 100644
--- a/modules/dnn/src/layers/detection_output_layer.cpp
+++ b/modules/dnn/src/layers/detection_output_layer.cpp
@@ -462,7 +462,7 @@ public:
             // Retrieve all prior bboxes
             std::vector<util::NormalizedBBox> priorBBoxes;
             std::vector<std::vector<float> > priorVariances;
-            GetPriorBBoxes(priorData, numPriors, _bboxesNormalized, priorBBoxes, priorVariances);
+            GetPriorBBoxes(priorData, numPriors, _bboxesNormalized, _varianceEncodedInTarget, priorBBoxes, priorVariances);
 
             // Decode all loc predictions to bboxes
             util::NormalizedBBox clipBounds;
@@ -756,7 +756,7 @@ public:
         CV_Assert(prior_bboxes.size() == prior_variances.size());
         CV_Assert(prior_bboxes.size() == bboxes.size());
         size_t num_bboxes = prior_bboxes.size();
-        CV_Assert(num_bboxes == 0 || prior_variances[0].size() == 4);
+        CV_Assert(num_bboxes == 0 || prior_variances[0].size() == 4 || variance_encoded_in_target);
         decode_bboxes.clear(); decode_bboxes.resize(num_bboxes);
         if(variance_encoded_in_target)
         {
@@ -808,12 +808,13 @@ public:
     }
 
     // Get prior bounding boxes from prior_data
-    //    prior_data: 1 x 2 x num_priors * 4 x 1 blob.
+    //    prior_data: 1 x 1 x num_priors * 4 x 1 blob or 1 x 2 x num_priors * 4 x 1 blob.
     //    num_priors: number of priors.
     //    prior_bboxes: stores all the prior bboxes in the format of util::NormalizedBBox.
     //    prior_variances: stores all the variances needed by prior bboxes.
     static void GetPriorBBoxes(const float* priorData, const int& numPriors,
-                        bool normalized_bbox, std::vector<util::NormalizedBBox>& priorBBoxes,
+                        bool normalized_bbox, bool variance_encoded_in_target,
+                        std::vector<util::NormalizedBBox>& priorBBoxes,
                         std::vector<std::vector<float> >& priorVariances)
     {
         priorBBoxes.clear(); priorBBoxes.resize(numPriors);
@@ -829,13 +830,16 @@ public:
             bbox.set_size(BBoxSize(bbox, normalized_bbox));
         }
 
-        for (int i = 0; i < numPriors; ++i)
+        if (!variance_encoded_in_target)
         {
-            int startIdx = (numPriors + i) * 4;
-            // not needed here: priorVariances[i].clear();
-            for (int j = 0; j < 4; ++j)
+            for (int i = 0; i < numPriors; ++i)
             {
-                priorVariances[i].push_back(priorData[startIdx + j]);
+                int startIdx = (numPriors + i) * 4;
+                // not needed here: priorVariances[i].clear();
+                for (int j = 0; j < 4; ++j)
+                {
+                    priorVariances[i].push_back(priorData[startIdx + j]);
+                }
             }
         }
     }
diff --git a/modules/dnn/src/layers/recurrent_layers.cpp b/modules/dnn/src/layers/recurrent_layers.cpp
index cb2ffb8cc9..6bfa48adbf 100644
--- a/modules/dnn/src/layers/recurrent_layers.cpp
+++ b/modules/dnn/src/layers/recurrent_layers.cpp
@@ -80,12 +80,31 @@ static void sigmoid(const Mat &src, Mat &dst)
     cv::pow(1 + dst, -1, dst);
 }
 
+typedef void (*ActivationFunction)(const Mat &src, Mat &dst);
+static ActivationFunction get_activation_function(const String& activation) {
+    // most used activations for PyTorch and TF : Tanh, Sigmoid
+    // if you need to support more optional activations use std::map instead
+    if (activation == "Tanh")
+    {
+        return tanh;
+    }
+    else if (activation == "Sigmoid")
+    {
+        return sigmoid;
+    }
+    else
+    {
+        CV_Error(Error::StsNotImplemented,
+                 cv::format("Activation function [%s] for layer LSTM  is not supported", activation.c_str()));
+    }
+}
+
 class LSTMLayerImpl CV_FINAL : public LSTMLayer
 {
     int numTimeStamps, numSamples;
     bool allocated;
 
-    MatShape outTailShape;                 //shape of single output sample
+    MatShape outTailShape;  //shape of single output sample
     MatShape outTsShape;    //shape of N output samples
 
     bool useTimestampDim;
@@ -95,6 +114,10 @@ class LSTMLayerImpl CV_FINAL : public LSTMLayer
     bool reverse;   // If true, go in negative direction along the time axis
     bool bidirectional;  // If true, produces both forward and reversed directions along time axis
 
+    ActivationFunction f_activation;
+    ActivationFunction g_activation;
+    ActivationFunction h_activation;
+
 public:
 
     LSTMLayerImpl(const LayerParams& params)
@@ -145,6 +168,20 @@ public:
         reverse = params.get<bool>("reverse", false);
         CV_Assert(!reverse || !bidirectional);
 
+        // read activations
+        DictValue activations = params.get<DictValue>("activations", "");
+        if (activations.size() == 1) // if activations wasn't specified use default
+        {
+            f_activation = sigmoid;
+            g_activation = tanh;
+            h_activation = tanh;
+        } else {
+            CV_Assert(activations.size() == 3);
+            f_activation = get_activation_function(activations.getStringValue(0));
+            g_activation = get_activation_function(activations.getStringValue(1));
+            h_activation = get_activation_function(activations.getStringValue(2));
+        }
+
         allocated = false;
         outTailShape.clear();
     }
@@ -339,15 +376,15 @@ public:
                     Mat gatesIF = gates.colRange(0, 2*numOut);
                     gemm(cInternal, blobs[5], 1, gateI, 1, gateI);
                     gemm(cInternal, blobs[6], 1, gateF, 1, gateF);
-                    sigmoid(gatesIF, gatesIF);
+                    f_activation(gatesIF, gatesIF);
                 }
                 else
                 {
                     Mat gatesIFO = gates.colRange(0, 3*numOut);
-                    sigmoid(gatesIFO, gatesIFO);
+                    f_activation(gatesIFO, gatesIFO);
                 }
 
-                tanh(gateG, gateG);
+                g_activation(gateG, gateG);
 
                 //compute c_t
                 multiply(gateF, cInternal, gateF);  // f_t (*) c_{t-1}
@@ -362,11 +399,11 @@ public:
                 if (usePeephole)
                 {
                     gemm(cInternal, blobs[7], 1, gateO, 1, gateO);
-                    sigmoid(gateO, gateO);
+                    f_activation(gateO, gateO);
                 }
 
                 //compute h_t
-                tanh(cInternal, hInternal);
+                h_activation(cInternal, hInternal);
                 multiply(gateO, hInternal, hInternal);
 
                 //save results in output blobs
diff --git a/modules/dnn/src/onnx/onnx_importer.cpp b/modules/dnn/src/onnx/onnx_importer.cpp
index dee7e128fa..946623fd40 100644
--- a/modules/dnn/src/onnx/onnx_importer.cpp
+++ b/modules/dnn/src/onnx/onnx_importer.cpp
@@ -254,6 +254,10 @@ static DictValue parse(const ::google::protobuf::RepeatedField< ::google::protob
     return DictValue::arrayInt(&dst[0], src.size());
 }
 
+static DictValue parseStr(const ::google::protobuf::RepeatedPtrField< ::std::string>& src) {
+    return DictValue::arrayString(src.begin(), static_cast<int>(src.size()));
+}
+
 LayerParams ONNXImporter::getLayerParams(const opencv_onnx::NodeProto& node_proto)
 {
     LayerParams lp;
@@ -313,6 +317,10 @@ LayerParams ONNXImporter::getLayerParams(const opencv_onnx::NodeProto& node_prot
                 CV_Assert(attribute_proto.ints_size() == 1 || attribute_proto.ints_size() == 2 || attribute_proto.ints_size() == 3);
                 lp.set("dilation", parse(attribute_proto.ints()));
             }
+            else if(attribute_name == "activations" && node_proto.op_type() == "LSTM")
+            {
+                lp.set(attribute_name, parseStr(attribute_proto.strings()));
+            }
             else if (attribute_proto.has_i())
             {
                 ::google::protobuf::int64 src = attribute_proto.i();
@@ -1176,18 +1184,32 @@ void ONNXImporter::parseLSTM(LayerParams& layerParams, const opencv_onnx::NodePr
     lstmParams.name += "/lstm";
 
     // https://pytorch.org/docs/stable/nn.html#lstm
-    CV_Assert(node_proto.input_size() == 7);
+    CV_Assert(node_proto.input_size() >= 7);
     Mat Wx = getBlob(node_proto, 1);
     Mat Wh = getBlob(node_proto, 2);
     Mat b = getBlob(node_proto, 3);
-    Mat h0 = getBlob(node_proto, 5);
-    Mat c0 = getBlob(node_proto, 6);
-
-    b = b.reshape(1, b.size[0]);
 
     const int numHidden = lstmParams.get<int>("hidden_size");
     const int numDirs = Wx.size[0];  // Is 1 for forward only and 2 for bidirectional LSTM.
     const int numFeatures = Wx.size[2];
+
+    Mat h0, c0;
+    if (!node_proto.input(5).empty()) {
+        h0 = getBlob(node_proto, 5);
+        h0 = h0.reshape(1, h0.size[0] * h0.size[1]);
+    } else {
+        // initial_h attribute can be empty in case of keras2onnx producer. fill it with zeros
+        h0 = Mat::zeros(numDirs * numFeatures, numHidden, CV_32FC1);
+    }
+    if (!node_proto.input(6).empty()) {
+        c0 = getBlob(node_proto, 6);
+        c0 = c0.reshape(1, c0.size[0] * c0.size[1]);
+    } else {
+        // initial_c attribute can be empty in case of keras2onnx producer. fill it with zeros
+        c0 = Mat::zeros(numDirs * numFeatures, numHidden, CV_32FC1);
+    }
+
+    b = b.reshape(1, b.size[0]);
     Mat bx = b.colRange(0, b.cols / 2);
     Mat bh = b.colRange(b.cols / 2, b.cols);
     b = bx + bh;
@@ -1215,8 +1237,7 @@ void ONNXImporter::parseLSTM(LayerParams& layerParams, const opencv_onnx::NodePr
     }
     Wx = Wx.reshape(1, Wx.size[0] * Wx.size[1]);
     Wh = Wh.reshape(1, Wh.size[0] * Wh.size[1]);
-    h0 = h0.reshape(1, h0.size[0] * h0.size[1]);
-    c0 = c0.reshape(1, c0.size[0] * c0.size[1]);
+
 
     lstmParams.blobs.resize(5);
     lstmParams.blobs[0] = Wh;
@@ -1224,6 +1245,9 @@ void ONNXImporter::parseLSTM(LayerParams& layerParams, const opencv_onnx::NodePr
     lstmParams.blobs[2] = b;
     lstmParams.blobs[3] = h0;
     lstmParams.blobs[4] = c0;
+
+    // read direction attribute
+    lstmParams.set("reverse", lstmParams.get<String>("direction", "") == "reverse");
     lstmParams.set("bidirectional", lstmParams.get<String>("direction", "") == "bidirectional");
 
     node_proto.set_output(0, lstmParams.name);  // set different name so output shapes will be registered on that name
diff --git a/modules/dnn/src/tensorflow/tf_importer.cpp b/modules/dnn/src/tensorflow/tf_importer.cpp
index 38a55d12b9..de7ec3dfcc 100644
--- a/modules/dnn/src/tensorflow/tf_importer.cpp
+++ b/modules/dnn/src/tensorflow/tf_importer.cpp
@@ -668,7 +668,7 @@ const TFImporter::DispatchMap TFImporter::buildDispatchMap()
     dispatch["PriorBox"] = &TFImporter::parsePriorBox;
     dispatch["Softmax"] = &TFImporter::parseSoftmax;
     dispatch["CropAndResize"] = &TFImporter::parseCropAndResize;
-    dispatch["Mean"] = dispatch["Sum"] = &TFImporter::parseMean;
+    dispatch["Mean"] = dispatch["Sum"] = dispatch["Max"] = &TFImporter::parseMean;
     dispatch["Pack"] = &TFImporter::parsePack;
     dispatch["ClipByValue"] = &TFImporter::parseClipByValue;
     dispatch["LeakyRelu"] = &TFImporter::parseLeakyRelu;
@@ -678,6 +678,7 @@ const TFImporter::DispatchMap TFImporter::buildDispatchMap()
     return dispatch;
 }
 
+// "Conv2D" "SpaceToBatchND" "DepthwiseConv2dNative" "Pad" "MirrorPad" "Conv3D"
 void TFImporter::parseConvolution(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer_, LayerParams& layerParams)
 {
     tensorflow::NodeDef layer = layer_;
@@ -897,6 +898,7 @@ void TFImporter::parseConvolution(tensorflow::GraphDef& net, const tensorflow::N
         data_layouts[name] = DATA_LAYOUT_NHWC;
 }
 
+// "BiasAdd" "Add" "AddV2" "Sub" "AddN"
 void TFImporter::parseBias(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
@@ -1108,6 +1110,7 @@ void TFImporter::parseReshape(tensorflow::GraphDef& net, const tensorflow::NodeD
     }
 }
 
+// "Flatten" "Squeeze"
 void TFImporter::parseFlatten(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
@@ -1266,6 +1269,7 @@ void TFImporter::parseLrn(tensorflow::GraphDef& net, const tensorflow::NodeDef&
     connectToAllBlobs(layer_id, dstNet, parsePin(layer.input(0)), id, num_inputs);
 }
 
+// "Concat" "ConcatV2"
 void TFImporter::parseConcat(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
@@ -1316,6 +1320,7 @@ void TFImporter::parseConcat(tensorflow::GraphDef& net, const tensorflow::NodeDe
     }
 }
 
+// "MaxPool" "MaxPool3D"
 void TFImporter::parseMaxPool(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
@@ -1337,6 +1342,7 @@ void TFImporter::parseMaxPool(tensorflow::GraphDef& net, const tensorflow::NodeD
     connectToAllBlobs(layer_id, dstNet, parsePin(inputName), id, num_inputs);
 }
 
+// "AvgPool" "AvgPool3D"
 void TFImporter::parseAvgPool(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
@@ -1523,6 +1529,7 @@ void TFImporter::parseStridedSlice(tensorflow::GraphDef& net, const tensorflow::
     connect(layer_id, dstNet, parsePin(layer.input(0)), id, 0);
 }
 
+// "Mul" "RealDiv"
 void TFImporter::parseMul(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
@@ -1680,6 +1687,7 @@ void TFImporter::parseMul(tensorflow::GraphDef& net, const tensorflow::NodeDef&
     }
 }
 
+// "FusedBatchNorm" "FusedBatchNormV3"
 void TFImporter::parseFusedBatchNorm(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     // op: "FusedBatchNorm"
@@ -1939,6 +1947,7 @@ void TFImporter::parseBlockLSTM(tensorflow::GraphDef& net, const tensorflow::Nod
     data_layouts[name] = DATA_LAYOUT_UNKNOWN;
 }
 
+// "ResizeNearestNeighbor" "ResizeBilinear" "FusedResizeAndPadConv2D"
 void TFImporter::parseResize(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer_, LayerParams& layerParams)
 {
     tensorflow::NodeDef layer = layer_;
@@ -2127,6 +2136,7 @@ void TFImporter::parseCropAndResize(tensorflow::GraphDef& net, const tensorflow:
     connect(layer_id, dstNet, parsePin(layer.input(1)), id, 1);
 }
 
+// "Mean" "Sum" "Max"
 void TFImporter::parseMean(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     // Computes the mean of elements across dimensions of a tensor.
@@ -2145,7 +2155,12 @@ void TFImporter::parseMean(tensorflow::GraphDef& net, const tensorflow::NodeDef&
     const std::string& name = layer.name();
     const std::string& type = layer.op();
     const int num_inputs = layer.input_size();
+    std::string pool_type = cv::toLowerCase(type);
 
+    if (pool_type == "mean")
+    {
+        pool_type = "ave";
+    }
     CV_CheckGT(num_inputs, 0, "");
 
     Mat indices = getTensorContent(getConstBlob(layer, value_id, 1));
@@ -2182,7 +2197,7 @@ void TFImporter::parseMean(tensorflow::GraphDef& net, const tensorflow::NodeDef&
         LayerParams avgLp;
         std::string avgName = name + "/avg";
         CV_Assert(layer_id.find(avgName) == layer_id.end());
-        avgLp.set("pool", type == "Mean" ? "ave" : "sum");
+        avgLp.set("pool", pool_type);
         // pooling kernel H x 1
         avgLp.set("global_pooling_h", true);
         avgLp.set("kernel_w", 1);
@@ -2223,7 +2238,7 @@ void TFImporter::parseMean(tensorflow::GraphDef& net, const tensorflow::NodeDef&
         int axis = toNCHW(indices.at<int>(0));
         if (axis == 2 || axis == 3)
         {
-            layerParams.set("pool", type == "Mean" ? "ave" : "sum");
+            layerParams.set("pool", pool_type);
             layerParams.set(axis == 2 ? "kernel_w" : "kernel_h", 1);
             layerParams.set(axis == 2 ? "global_pooling_h" : "global_pooling_w", true);
             int id = dstNet.addLayer(name, "Pooling", layerParams);
@@ -2255,7 +2270,7 @@ void TFImporter::parseMean(tensorflow::GraphDef& net, const tensorflow::NodeDef&
             Pin inpId = parsePin(layer.input(0));
             addPermuteLayer(order, name + "/nhwc", inpId);
 
-            layerParams.set("pool", type == "Mean" ? "ave" : "sum");
+            layerParams.set("pool", pool_type);
             layerParams.set("kernel_h", 1);
             layerParams.set("global_pooling_w", true);
             int id = dstNet.addLayer(name, "Pooling", layerParams);
@@ -2285,7 +2300,7 @@ void TFImporter::parseMean(tensorflow::GraphDef& net, const tensorflow::NodeDef&
         if (indices.total() != 2 || indices.at<int>(0) != 1 || indices.at<int>(1) != 2)
             CV_Error(Error::StsNotImplemented, "Unsupported mode of reduce_mean or reduce_sum operation.");
 
-        layerParams.set("pool", type == "Mean" ? "ave" : "sum");
+        layerParams.set("pool", pool_type);
         layerParams.set("global_pooling", true);
         int id = dstNet.addLayer(name, "Pooling", layerParams);
         layer_id[name] = id;
@@ -2389,6 +2404,7 @@ void TFImporter::parseLeakyRelu(tensorflow::GraphDef& net, const tensorflow::Nod
     connectToAllBlobs(layer_id, dstNet, parsePin(layer.input(0)), id, num_inputs);
 }
 
+// "Abs" "Tanh" "Sigmoid" "Relu" "Elu" "Exp" "Identity" "Relu6"
 void TFImporter::parseActivation(tensorflow::GraphDef& net, const tensorflow::NodeDef& layer, LayerParams& layerParams)
 {
     const std::string& name = layer.name();
diff --git a/modules/dnn/test/test_onnx_importer.cpp b/modules/dnn/test/test_onnx_importer.cpp
index 0e252cca83..26e5fb632c 100644
--- a/modules/dnn/test/test_onnx_importer.cpp
+++ b/modules/dnn/test/test_onnx_importer.cpp
@@ -700,6 +700,11 @@ TEST_P(Test_ONNX_layers, Split_EltwiseMax)
     testONNXModels("split_max");
 }
 
+TEST_P(Test_ONNX_layers, LSTM_Activations)
+{
+    testONNXModels("lstm_cntk_tanh", pb, 0, 0, false, false);
+}
+
 TEST_P(Test_ONNX_layers, LSTM)
 {
     testONNXModels("lstm", npy, 0, 0, false, false);
diff --git a/modules/dnn/test/test_tf_importer.cpp b/modules/dnn/test/test_tf_importer.cpp
index 53cc05bfc3..3f33f16774 100644
--- a/modules/dnn/test/test_tf_importer.cpp
+++ b/modules/dnn/test/test_tf_importer.cpp
@@ -128,6 +128,13 @@ TEST_P(Test_TensorFlow_layers, reduce_mean)
     runTensorFlowNet("global_pool_by_axis");
 }
 
+TEST_P(Test_TensorFlow_layers, reduce_max)
+{
+    if (backend == DNN_BACKEND_INFERENCE_ENGINE_NN_BUILDER_2019)
+        applyTestTag(CV_TEST_TAG_DNN_SKIP_IE_NN_BUILDER);
+    runTensorFlowNet("max_pool_by_axis");
+}
+
 TEST_P(Test_TensorFlow_layers, reduce_sum)
 {
     if (backend == DNN_BACKEND_INFERENCE_ENGINE_NN_BUILDER_2019)
@@ -135,11 +142,21 @@ TEST_P(Test_TensorFlow_layers, reduce_sum)
     runTensorFlowNet("sum_pool_by_axis");
 }
 
+TEST_P(Test_TensorFlow_layers, reduce_max_channel)
+{
+    runTensorFlowNet("reduce_max_channel");
+}
+
 TEST_P(Test_TensorFlow_layers, reduce_sum_channel)
 {
     runTensorFlowNet("reduce_sum_channel");
 }
 
+TEST_P(Test_TensorFlow_layers, reduce_max_channel_keep_dims)
+{
+    runTensorFlowNet("reduce_max_channel", false, 0.0, 0.0, false, "_keep_dims");
+}
+
 TEST_P(Test_TensorFlow_layers, reduce_sum_channel_keep_dims)
 {
     runTensorFlowNet("reduce_sum_channel", false, 0.0, 0.0, false, "_keep_dims");
@@ -395,6 +412,11 @@ TEST_P(Test_TensorFlow_layers, pooling_reduce_mean)
     runTensorFlowNet("reduce_mean");  // an average pooling over all spatial dimensions.
 }
 
+TEST_P(Test_TensorFlow_layers, pooling_reduce_max)
+{
+    runTensorFlowNet("reduce_max");  // a MAX pooling over all spatial dimensions.
+}
+
 TEST_P(Test_TensorFlow_layers, pooling_reduce_sum)
 {
     runTensorFlowNet("reduce_sum");  // a SUM pooling over all spatial dimensions.
diff --git a/modules/imgproc/include/opencv2/imgproc.hpp b/modules/imgproc/include/opencv2/imgproc.hpp
index 88c960747c..19f3b1a9bf 100644
--- a/modules/imgproc/include/opencv2/imgproc.hpp
+++ b/modules/imgproc/include/opencv2/imgproc.hpp
@@ -2303,7 +2303,7 @@ enlarge an image, it will generally look best with c#INTER_CUBIC (slow) or #INTE
 @param src input image.
 @param dst output image; it has the size dsize (when it is non-zero) or the size computed from
 src.size(), fx, and fy; the type of dst is the same as of src.
-@param dsize output image size; if it equals zero, it is computed as:
+@param dsize output image size; if it equals zero (`None` in Python), it is computed as:
  \f[\texttt{dsize = Size(round(fx*src.cols), round(fy*src.rows))}\f]
  Either dsize or both fx and fy must be non-zero.
 @param fx scale factor along the horizontal axis; when it equals 0, it is computed as
@@ -3897,6 +3897,7 @@ hierarchy[i][0] , hierarchy[i][1] , hierarchy[i][2] , and hierarchy[i][3] are se
 in contours of the next and previous contours at the same hierarchical level, the first child
 contour and the parent contour, respectively. If for the contour i there are no next, previous,
 parent, or nested contours, the corresponding elements of hierarchy[i] will be negative.
+@note In Python, hierarchy is nested inside a top level array. Use hierarchy[0][i] to access hierarchical elements of i-th contour.
 @param mode Contour retrieval mode, see #RetrievalModes
 @param method Contour approximation method, see #ContourApproximationModes
 @param offset Optional offset by which every contour point is shifted. This is useful if the
diff --git a/modules/imgproc/src/rotcalipers.cpp b/modules/imgproc/src/rotcalipers.cpp
index 527f71a247..e3d81c7e0c 100644
--- a/modules/imgproc/src/rotcalipers.cpp
+++ b/modules/imgproc/src/rotcalipers.cpp
@@ -88,6 +88,32 @@ enum { CALIPERS_MAXHEIGHT=0, CALIPERS_MINAREARECT=1, CALIPERS_MAXDIST=2 };
  //    Notes:
  //F*/
 
+static void rotate90CCW(const cv::Point2f& in, cv::Point2f &out)
+{
+    out.x = -in.y;
+    out.y = in.x;
+}
+
+static void rotate90CW(const cv::Point2f& in, cv::Point2f &out)
+{
+    out.x = in.y;
+    out.y = -in.x;
+}
+
+static void rotate180(const cv::Point2f& in, cv::Point2f &out)
+{
+    out.x = -in.x;
+    out.y = -in.y;
+}
+
+/* return true if first vector is to the right (clockwise) of the second */
+static bool firstVecIsRight(const cv::Point2f& vec1, const cv::Point2f &vec2)
+{
+    cv::Point2f tmp;
+    rotate90CW(vec1, tmp);
+    return tmp.x * vec2.x + tmp.y * vec2.y < 0;
+}
+
 /* we will use usual cartesian coordinates */
 static void rotatingCalipers( const Point2f* points, int n, int mode, float* out )
 {
@@ -100,6 +126,7 @@ static void rotatingCalipers( const Point2f* points, int n, int mode, float* out
     Point2f* vect = (Point2f*)(inv_vect_length + n);
     int left = 0, bottom = 0, right = 0, top = 0;
     int seq[4] = { -1, -1, -1, -1 };
+    Point2f rot_vect[4];
 
     /* rotating calipers sides will always have coordinates
      (a,b) (-b,a) (-a,-b) (b, -a)
@@ -179,32 +206,18 @@ static void rotatingCalipers( const Point2f* points, int n, int mode, float* out
     /* all of edges will be checked while rotating calipers by 90 degrees */
     for( k = 0; k < n; k++ )
     {
-        /* sinus of minimal angle */
-        /*float sinus;*/
-
-        /* compute cosine of angle between calipers side and polygon edge */
-        /* dp - dot product */
-        float dp[4] = {
-            +base_a * vect[seq[0]].x + base_b * vect[seq[0]].y,
-            -base_b * vect[seq[1]].x + base_a * vect[seq[1]].y,
-            -base_a * vect[seq[2]].x - base_b * vect[seq[2]].y,
-            +base_b * vect[seq[3]].x - base_a * vect[seq[3]].y,
-        };
-
-        float maxcos = dp[0] * inv_vect_length[seq[0]];
-
         /* number of calipers edges, that has minimal angle with edge */
         int main_element = 0;
 
-        /* choose minimal angle */
-        for ( i = 1; i < 4; ++i )
+        /* choose minimum angle between calipers side and polygon edge by dot product sign */
+        rot_vect[0] = vect[seq[0]];
+        rotate90CW(vect[seq[1]], rot_vect[1]);
+        rotate180(vect[seq[2]], rot_vect[2]);
+        rotate90CCW(vect[seq[3]], rot_vect[3]);
+        for (i = 1; i < 4; i++)
         {
-            float cosalpha = dp[i] * inv_vect_length[seq[i]];
-            if (cosalpha > maxcos)
-            {
+            if (firstVecIsRight(rot_vect[i], rot_vect[main_element]))
                 main_element = i;
-                maxcos = cosalpha;
-            }
         }
 
         /*rotate calipers*/
diff --git a/modules/imgproc/test/test_convhull.cpp b/modules/imgproc/test/test_convhull.cpp
index 9c3f060e60..0f379cd02b 100644
--- a/modules/imgproc/test/test_convhull.cpp
+++ b/modules/imgproc/test/test_convhull.cpp
@@ -2384,5 +2384,78 @@ TEST(Imgproc_minAreaRect, reproducer_18157)
     EXPECT_TRUE(checkMinAreaRect(rr, contour)) << rr.center << " " << rr.size << " " << rr.angle;
 }
 
+TEST(Imgproc_minAreaRect, reproducer_19769_lightweight)
+{
+    const int N = 23;
+    float pts_[N][2] = {
+            {1325, 732}, {1248, 808}, {582, 1510}, {586, 1524},
+            {595, 1541}, {599, 1547}, {789, 1745}, {829, 1786},
+            {997, 1958}, {1116, 2074}, {1207, 2066}, {1216, 2058},
+            {1231, 2044}, {1265, 2011}, {2036, 1254}, {2100, 1191},
+            {2169, 1123}, {2315, 979}, {2395, 900}, {2438, 787},
+            {2434, 782}, {2416, 762}, {2266, 610}
+    };
+    Mat contour(N, 1, CV_32FC2, (void*)pts_);
+
+    RotatedRect rr = cv::minAreaRect(contour);
+
+    EXPECT_TRUE(checkMinAreaRect(rr, contour)) << rr.center << " " << rr.size << " " << rr.angle;
+}
+
+TEST(Imgproc_minAreaRect, reproducer_19769)
+{
+    const int N = 169;
+    float pts_[N][2] = {
+            {1854, 227}, {1850, 228}, {1847, 229}, {1835, 235},
+            {1832, 237}, {1829, 239}, {1825, 242}, {1818, 248},
+            {1807, 258}, {1759, 306}, {1712, 351}, {1708, 356},
+            {1658, 404}, {1655, 408}, {1602, 459}, {1599, 463},
+            {1542, 518}, {1477, 582}, {1402, 656}, {1325, 732},
+            {1248, 808}, {1161, 894}, {1157, 898}, {1155, 900},
+            {1068, 986}, {1060, 995}, {1058, 997}, {957, 1097},
+            {956, 1097}, {814, 1238}, {810, 1242}, {805, 1248},
+            {610, 1442}, {603, 1450}, {599, 1455}, {596, 1459},
+            {594, 1462}, {592, 1465}, {590, 1470}, {588, 1472},
+            {586, 1476}, {586, 1478}, {584, 1481}, {583, 1485},
+            {582, 1490}, {582, 1510}, {583, 1515}, {584, 1518},
+            {585, 1521}, {586, 1524}, {593, 1538}, {595, 1541},
+            {597, 1544}, {599, 1547}, {603, 1552}, {609, 1559},
+            {623, 1574}, {645, 1597}, {677, 1630}, {713, 1667},
+            {753, 1707}, {789, 1744}, {789, 1745}, {829, 1786},
+            {871, 1828}, {909, 1867}, {909, 1868}, {950, 1910},
+            {953, 1912}, {997, 1958}, {1047, 2009}, {1094, 2056},
+            {1105, 2066}, {1110, 2070}, {1113, 2072}, {1116, 2074},
+            {1119, 2076}, {1122, 2077}, {1124, 2079}, {1130, 2082},
+            {1133, 2083}, {1136, 2084}, {1139, 2085}, {1142, 2086},
+            {1148, 2087}, {1166, 2087}, {1170, 2086}, {1174, 2085},
+            {1177, 2084}, {1180, 2083}, {1188, 2079}, {1190, 2077},
+            {1193, 2076}, {1196, 2074}, {1199, 2072}, {1202, 2070},
+            {1207, 2066}, {1216, 2058}, {1231, 2044}, {1265, 2011},
+            {1314, 1962}, {1360, 1917}, {1361, 1917}, {1408, 1871},
+            {1457, 1822}, {1508, 1773}, {1512, 1768}, {1560, 1722},
+            {1617, 1665}, {1671, 1613}, {1730, 1554}, {1784, 1502},
+            {1786, 1500}, {1787, 1498}, {1846, 1440}, {1850, 1437},
+            {1908, 1380}, {1974, 1314}, {2034, 1256}, {2036, 1254},
+            {2100, 1191}, {2169, 1123}, {2242, 1051}, {2315, 979},
+            {2395, 900}, {2426, 869}, {2435, 859}, {2438, 855},
+            {2440, 852}, {2442, 849}, {2443, 846}, {2445, 844},
+            {2446, 842}, {2446, 840}, {2448, 837}, {2449, 834},
+            {2450, 829}, {2450, 814}, {2449, 809}, {2448, 806},
+            {2447, 803}, {2442, 793}, {2440, 790}, {2438, 787},
+            {2434, 782}, {2428, 775}, {2416, 762}, {2411, 758},
+            {2342, 688}, {2340, 686}, {2338, 684}, {2266, 610},
+            {2260, 605}, {2170, 513}, {2075, 417}, {2073, 415},
+            {2069, 412}, {1955, 297}, {1955, 296}, {1913, 254},
+            {1904, 246}, {1897, 240}, {1894, 238}, {1891, 236},
+            {1888, 234}, {1880, 230}, {1877, 229}, {1874, 228},
+            {1870, 227}
+    };
+    Mat contour(N, 1, CV_32FC2, (void*)pts_);
+
+    RotatedRect rr = cv::minAreaRect(contour);
+
+    EXPECT_TRUE(checkMinAreaRect(rr, contour)) << rr.center << " " << rr.size << " " << rr.angle;
+}
+
 }} // namespace
 /* End of file. */
diff --git a/modules/ml/misc/java/test/MLTest.java b/modules/ml/misc/java/test/MLTest.java
index 2b08543a84..504805dffa 100644
--- a/modules/ml/misc/java/test/MLTest.java
+++ b/modules/ml/misc/java/test/MLTest.java
@@ -36,7 +36,7 @@ public class MLTest extends OpenCVTestCase {
         String filename = OpenCVTestRunner.getTempFileName("yml");
         saved.save(filename);
         SVM loaded = SVM.load(filename);
-        assertTrue(saved.isTrained());
+        assertTrue(loaded.isTrained());
     }
 
 }