Adds dnn inference module for simple convolutional networks. Reimplements srcnn filter based on it.

Signed-off-by: Pedro Arthur <bygrandao@gmail.com>

libavfilter/dnn_interface.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2018 Sergey Lavrushkin
+ *
+ * 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
+ * DNN inference engine interface.
+ */
+
+#ifndef AVFILTER_DNN_INTERFACE_H
+#define AVFILTER_DNN_INTERFACE_H
+
+typedef enum {DNN_SUCCESS, DNN_ERROR} DNNReturnType;
+
+typedef enum {DNN_NATIVE} DNNBackendType;
+
+typedef enum {DNN_SRCNN} DNNDefaultModel;
+
+typedef struct DNNData{
+    float* data;
+    int width, height, channels;
+} DNNData;
+
+
+typedef struct DNNModel{
+    // Stores model that can be different for different backends.
+    void* model;
+    // Sets model input and output, while allocating additional memory for intermediate calculations.
+    // Should be called at least once before model execution.
+    DNNReturnType (*set_input_output)(void* model, const DNNData* input, const DNNData* output);
+} DNNModel;
+
+// Stores pointers to functions for loading, executing, freeing DNN models for one of the backends.
+typedef struct DNNModule{
+    // Loads model and parameters from given file. Returns NULL if it is not possible.
+    DNNModel* (*load_model)(const char* model_filename);
+    // Loads one of the default models
+    DNNModel* (*load_default_model)(DNNDefaultModel model_type);
+    // Executes model with specified input and output. Returns DNN_ERROR otherwise.
+    DNNReturnType (*execute_model)(const DNNModel* model);
+    // Frees memory allocated for model.
+    void (*free_model)(DNNModel** model);
+} DNNModule;
+
+// Initializes DNNModule depending on chosen backend.
+DNNModule* ff_get_dnn_module(DNNBackendType backend_type);
+
+#endif