dnn: add layer pad which is equivalent to tf.pad

the reason to add this layer first is that vf_sr uses it in its
tensorflow model, and the next plan is to update the python script
to convert tf.pad into native model.
Signed-off-by: Guo, Yejun <yejun.guo@intel.com>
Signed-off-by: Pedro Arthur <bygrandao@gmail.com>

libavfilter/dnn/Makefile

 OBJS-$(CONFIG_DNN)                           += dnn/dnn_interface.o
 OBJS-$(CONFIG_DNN)                           += dnn/dnn_backend_native.o
+OBJS-$(CONFIG_DNN)                           += dnn/dnn_backend_native_layer_pad.o
 
 DNN-OBJS-$(CONFIG_LIBTENSORFLOW)             += dnn/dnn_backend_tf.o
 

libavfilter/dnn/dnn_backend_native_layer_pad.c

+/*
+ * Copyright (c) 2019 Guo Yejun
+ *
+ * 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 <string.h>
+#include "libavutil/avassert.h"
+#include "dnn_backend_native_layer_pad.h"
+
+static int before_get_buddy(int given, int paddings, LayerPadModeParam mode)
+{
+    if (mode == LPMP_SYMMETRIC) {
+        return (2 * paddings - 1 - given);
+    } else if (mode == LPMP_REFLECT) {
+        return (2 * paddings - given);
+    } else {
+        av_assert0(!"should not reach here");
+        return 0;
+    }
+}
+
+static int after_get_buddy(int given, int border, LayerPadModeParam mode)
+{
+    if (mode == LPMP_SYMMETRIC) {
+        int offset = given - border;
+        return (border - 1 - offset);
+    } else if (mode == LPMP_REFLECT) {
+        int offset = given - border;
+        return (border - 2 - offset);
+    } else {
+        av_assert0(!"should not reach here");
+        return 0;
+    }
+}
+
+void dnn_execute_layer_pad(const float *input, float *output, const LayerPadParams *params, int number, int height, int width, int channel)
+{
+    int32_t before_paddings;
+    int32_t after_paddings;
+
+    // suppose format is <N, H, W, C>
+    int new_number = number + params->paddings[0][0] + params->paddings[0][1];
+    int new_height = height + params->paddings[1][0] + params->paddings[1][1];
+    int new_width = width + params->paddings[2][0] + params->paddings[2][1];
+    int new_channel = channel + params->paddings[3][0] + params->paddings[3][1];
+
+    int c_stride = channel;
+    int wc_stride = c_stride * width;
+    int hwc_stride = wc_stride * height;
+
+    int new_c_stride = new_channel;
+    int new_wc_stride = new_c_stride * new_width;
+    int new_hwc_stride = new_wc_stride * new_height;
+
+    // copy the original data
+    for (int n = 0; n < number; n++) {
+        for (int h = 0; h < height; h++) {
+            for (int w = 0; w < width; w++) {
+                const float *src = input + n * hwc_stride + h * wc_stride + w * c_stride;
+                float *dst = output + (n + params->paddings[0][0]) * new_hwc_stride
+                                    + (h + params->paddings[1][0]) * new_wc_stride
+                                    + (w + params->paddings[2][0]) * new_c_stride
+                                    + params->paddings[3][0];
+                memcpy(dst, src, channel * sizeof(float));
+            }
+        }
+    }
+
+    // handle the first dimension
+    before_paddings = params->paddings[0][0];
+    after_paddings = params->paddings[0][1];
+    for (int n = 0; n < before_paddings; n++) {
+        float *dst = output + n * new_hwc_stride;
+        if (params->mode == LPMP_CONSTANT) {
+            for (int i = 0; i < new_hwc_stride; i++) {
+                dst[i] = params->constant_values;
+            }
+        }
+        else {
+            int buddy = before_get_buddy(n, before_paddings, params->mode);
+            float *src = output + buddy * new_hwc_stride;
+            memcpy(dst, src, new_hwc_stride * sizeof(float));
+        }
+    }
+    for (int n = 0; n < after_paddings; n++) {
+        int given = number + before_paddings + n;
+        float *dst = output + given * new_hwc_stride;
+        if (params->mode == LPMP_CONSTANT) {
+            for (int i = 0; i < new_hwc_stride; i++) {
+                dst[i] = params->constant_values;
+            }
+        } else {
+            int buddy = after_get_buddy(given, number + before_paddings, params->mode);
+            float *src = output + buddy * new_hwc_stride;
+            memcpy(dst, src, new_hwc_stride * sizeof(float));
+        }
+    }
+
+    // handle the second dimension
+    before_paddings = params->paddings[1][0];
+    after_paddings = params->paddings[1][1];
+    for (int n = 0; n < new_number; n++) {
+        float *start = output + n * new_hwc_stride;
+        for (int h = 0; h < before_paddings; h++) {
+            float *dst = start + h * new_wc_stride;
+            if (params->mode == LPMP_CONSTANT) {
+                for (int i = 0; i < new_wc_stride; i++) {
+                    dst[i] = params->constant_values;
+                }
+            } else {
+                int buddy = before_get_buddy(h, before_paddings, params->mode);
+                float *src = start + buddy * new_wc_stride;
+                memcpy(dst, src, new_wc_stride * sizeof(float));
+            }
+        }
+        for (int h = 0; h < after_paddings; h++) {
+            int given = height + before_paddings + h;
+            float *dst = start + given * new_wc_stride;
+            if (params->mode == LPMP_CONSTANT) {
+                for (int i = 0; i < new_wc_stride; i++) {
+                    dst[i] = params->constant_values;
+                }
+            } else {
+                int buddy = after_get_buddy(given, height + before_paddings, params->mode);
+                float *src = start + buddy * new_wc_stride;
+                memcpy(dst, src, new_wc_stride * sizeof(float));
+            }
+        }
+    }
+
+    // handle the third dimension
+    before_paddings = params->paddings[2][0];
+    after_paddings = params->paddings[2][1];
+    for (int n = 0; n < new_number; n++) {
+        for (int h = 0; h < new_height; h++) {
+            float *start = output + n * new_hwc_stride + h * new_wc_stride;
+            for (int w = 0; w < before_paddings; w++) {
+                float *dst = start + w * new_c_stride;
+                if (params->mode == LPMP_CONSTANT) {
+                    for (int i = 0; i < new_c_stride; i++) {
+                        dst[i] = params->constant_values;
+                    }
+                } else {
+                    int buddy = before_get_buddy(w, before_paddings, params->mode);
+                    float *src = start + buddy * new_c_stride;
+                    memcpy(dst, src, new_c_stride * sizeof(float));
+                }
+            }
+            for (int w = 0; w < after_paddings; w++) {
+                int given = width + before_paddings + w;
+                float *dst = start + given * new_c_stride;
+                if (params->mode == LPMP_CONSTANT) {
+                    for (int i = 0; i < new_c_stride; i++) {
+                        dst[i] = params->constant_values;
+                    }
+                } else {
+                    int buddy = after_get_buddy(given, width + before_paddings, params->mode);
+                    float *src = start + buddy * new_c_stride;
+                    memcpy(dst, src, new_c_stride * sizeof(float));
+                }
+            }
+        }
+    }
+
+    // handle the fourth dimension
+    before_paddings = params->paddings[3][0];
+    after_paddings = params->paddings[3][1];
+    for (int n = 0; n < new_number; n++) {
+        for (int h = 0; h < new_height; h++) {
+            for (int w = 0; w < new_width; w++) {
+                float *start = output + n * new_hwc_stride + h * new_wc_stride + w * new_c_stride;
+                for (int c = 0; c < before_paddings; c++) {
+                    float *dst = start + c;
+                    if (params->mode == LPMP_CONSTANT) {
+                        *dst = params->constant_values;
+                    } else {
+                        int buddy = before_get_buddy(c, before_paddings, params->mode);
+                        float *src = start + buddy;
+                        *dst = *src;
+                    }
+                }
+                for (int c = 0; c < after_paddings; c++) {
+                    int given = channel + before_paddings + c;
+                    float *dst = start + given;
+                    if (params->mode == LPMP_CONSTANT) {
+                        *dst = params->constant_values;
+                    } else {
+                        int buddy = after_get_buddy(given, channel + before_paddings, params->mode);
+                        float *src = start + buddy;
+                        *dst = *src;
+                    }
+                }
+            }
+        }
+    }
+}

libavfilter/dnn/dnn_backend_native_layer_pad.h

+/*
+ * Copyright (c) 2019 Guo Yejun
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * layer pad (equivalent to tf.pad) for native backend.
+ */
+#ifndef AVFILTER_DNN_DNN_BACKEND_NATIVE_LAYER_PAD_H
+#define AVFILTER_DNN_DNN_BACKEND_NATIVE_LAYER_PAD_H
+
+#include <stdint.h>
+
+typedef enum {LPMP_CONSTANT, LPMP_REFLECT, LPMP_SYMMETRIC} LayerPadModeParam;
+
+typedef struct LayerPadParams{
+    int32_t paddings[4][2];
+    LayerPadModeParam mode;
+    float constant_values;
+} LayerPadParams;
+
+void dnn_execute_layer_pad(const float *input, float *output, const LayerPadParams *params, int number, int height, int width, int channel);
+
+#endif