libavformat: Add an example how to use the metadata API

Also include it into the doxygen documentation
(cherry picked from commit 12489443de)

libavformat/Makefile

@@ -335,7 +335,7 @@ OBJS-$(CONFIG_UDP_PROTOCOL)              += udp.o
 # libavdevice dependencies
 OBJS-$(CONFIG_JACK_INDEV)                += timefilter.o
 
-EXAMPLES  = output
+EXAMPLES  = metadata output
 TESTPROGS = timefilter
 
 include $(SUBDIR)../subdir.mak

libavformat/avformat.h

@@ -109,6 +109,8 @@ struct AVFormatContext;
  variant_bitrate -- the total bitrate of the bitrate variant that the current stream is part of
  @endverbatim
  *
+ * Look in the examples section for an application example how to use the Metadata API.
+ *
  * @}
  */
 

libavformat/metadata-example.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2011 Reinhard Tartler
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * @file
+ * @example libavformat/metadata-example.c
+ * Shows how the metadata API can be used in application programs.
+ */
+
+#include <stdio.h>
+
+#include <libavformat/avformat.h>
+#include <libavutil/dict.h>
+
+int main (int argc, char **argv)
+{
+    AVFormatContext *fmt_ctx = NULL;
+    AVDictionaryEntry *tag = NULL;
+    int ret;
+
+    if (argc != 2) {
+        printf("usage: %s <input_file>\n"
+               "example program to demonstrate the use of the libavformat metadata API.\n"
+               "\n", argv[0]);
+        return 1;
+    }
+
+    av_register_all();
+    if ((ret = avformat_open_input(&fmt_ctx, argv[1], NULL, NULL)))
+        return ret;
+
+    while ((tag = av_dict_get(fmt_ctx->metadata, "", tag, AV_DICT_IGNORE_SUFFIX)))
+        printf("%s=%s\n", tag->key, tag->value);
+
+    avformat_free_context(fmt_ctx);
+    return 0;
+}