avfilter/dnn/dnn_backend_tf: simplify the code with ff_hex_to_data

please use tools/python/tf_sess_config.py to get the sess_config after that.
note the byte order of session config is in normal order.
bump the MICRO version for the config change.

Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

libavfilter/dnn/dnn_backend_tf.c

@@ -28,6 +28,7 @@
 #include "dnn_backend_native_layer_conv2d.h"
 #include "dnn_backend_native_layer_depth2space.h"
 #include "libavformat/avio.h"
+#include "libavformat/internal.h"
 #include "libavutil/avassert.h"
 #include "../internal.h"
 #include "dnn_backend_native_layer_pad.h"
@@ -206,53 +207,26 @@ static DNNReturnType load_tf_model(TFModel *tf_model, const char *model_filename
 
     // prepare the sess config data
     if (tf_model->ctx.options.sess_config != NULL) {
+        const char *config;
         /*
         tf_model->ctx.options.sess_config is hex to present the serialized proto
         required by TF_SetConfig below, so we need to first generate the serialized
-        proto in a python script, the following is a script example to generate
-        serialized proto which specifies one GPU, we can change the script to add
-        more options.
-
-        import tensorflow as tf
-        gpu_options = tf.GPUOptions(visible_device_list='0')
-        config = tf.ConfigProto(gpu_options=gpu_options)
-        s = config.SerializeToString()
-        b = ''.join("%02x" % int(ord(b)) for b in s[::-1])
-        print('0x%s' % b)
-
-        the script output looks like: 0xab...cd, and then pass 0xab...cd to sess_config.
+        proto in a python script, tools/python/tf_sess_config.py is a script example
+        to generate the configs of sess_config.
         */
-        char tmp[3];
-        tmp[2] = '\0';
-
         if (strncmp(tf_model->ctx.options.sess_config, "0x", 2) != 0) {
             av_log(ctx, AV_LOG_ERROR, "sess_config should start with '0x'\n");
             return DNN_ERROR;
         }
+        config = tf_model->ctx.options.sess_config + 2;
+        sess_config_length = ff_hex_to_data(NULL, config);
 
-        sess_config_length = strlen(tf_model->ctx.options.sess_config);
-        if (sess_config_length % 2 != 0) {
-            av_log(ctx, AV_LOG_ERROR, "the length of sess_config is not even (%s), "
-                                      "please re-generate the config.\n",
-                                      tf_model->ctx.options.sess_config);
-            return DNN_ERROR;
-        }
-
-        sess_config_length -= 2; //ignore the first '0x'
-        sess_config_length /= 2; //get the data length in byte
-
-        sess_config = av_malloc(sess_config_length);
+        sess_config = av_mallocz(sess_config_length + AV_INPUT_BUFFER_PADDING_SIZE);
         if (!sess_config) {
             av_log(ctx, AV_LOG_ERROR, "failed to allocate memory\n");
             return DNN_ERROR;
         }
-
-        for (int i = 0; i < sess_config_length; i++) {
-            int index = 2 + (sess_config_length - 1 - i) * 2;
-            tmp[0] = tf_model->ctx.options.sess_config[index];
-            tmp[1] = tf_model->ctx.options.sess_config[index + 1];
-            sess_config[i] = strtol(tmp, NULL, 16);
-        }
+        ff_hex_to_data(sess_config, config);
     }
 
     graph_def = read_graph(model_filename);

libavfilter/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR   8
 #define LIBAVFILTER_VERSION_MINOR   0
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

tools/python/tf_sess_config.py

@@ -0,0 +1,45 @@
+# Copyright (c) 2021
+#
+# 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
+# ==============================================================================
+
+# verified with Python 3.6.8 on CentOS 7.2
+import tensorflow as tf
+
+visible_device_list = '0' # use , separator for more GPUs like '0, 1'
+per_process_gpu_memory_fraction = 0.9 # avoid out of memory
+intra_op_parallelism_threads = 2  # default in tensorflow
+inter_op_parallelism_threads = 5  # default in tensorflow
+
+gpu_options = tf.compat.v1.GPUOptions(
+              per_process_gpu_memory_fraction = per_process_gpu_memory_fraction,
+              visible_device_list = visible_device_list,
+              allow_growth = True)
+
+config = tf.compat.v1.ConfigProto(
+         allow_soft_placement = True,
+         log_device_placement = False,
+         intra_op_parallelism_threads = intra_op_parallelism_threads,
+         inter_op_parallelism_threads = inter_op_parallelism_threads,
+         gpu_options = gpu_options)
+
+s = config.SerializeToString()
+# print(list(map(hex, s)))  # print by json if need
+
+print('a serialized protobuf string for TF_SetConfig, note the byte order is in normal order.')
+b = ''.join(format(b,'02x') for b in s)
+print('0x%s' % b) # print by hex format