iridium-extractor: add generate-sigmf-meta feature

apps/iridium-extractor

@@ -149,6 +149,8 @@ if __name__ == "__main__":
                         help='Sample rate of the source or the file in Hz. Must be divisible by 100000.')
     parser.add_argument('--raw-capture', dest='raw_capture_filename', action="store",
                         help='Write a copy of the samples to a SigMF recording.')
+    parser.add_argument('--generate-sigmf-meta', dest='sigmf_meta_filename', action="store",
+                        help='Create a sigm-meta file based on the input format.')
     parser.add_argument('-v', '--verbose', dest='verbose', action='store_true',
                         help='Enable verbose output.')
 
@@ -337,6 +339,39 @@ if __name__ == "__main__":
             print("/tmp/signals directory missing!", file=sys.stderr)
             exit(1)
 
+    if args.sigmf_meta_filename is not None:
+        import json
+        import datetime
+        dt = None
+        if args.file_info is not None and (g := re.search(r"i-(\d+(\.\d+)?)-", args.file_info)):
+            try:
+                dt = datetime.datetime.fromtimestamp(float(g.group(1)), datetime.timezone.utc)
+            except ValueError:
+                pass
+        if dt is None:
+            dt = datetime.datetime.fromtimestamp(os.path.getctime(filename), datetime.timezone.utc)
+
+        data = {
+            'global': {
+                'core:datatype': fmt,
+                'core:description': 'autogenerated for ' + os.path.basename(filename),
+                'core:recorder': 'iridium-extractor',
+                "core:num_channels": 1,
+                'core:sample_rate': sample_rate,
+                'core:version': '1.0.0'
+            },
+            'captures': [
+                {
+                    'core:datetime': datetime.datetime.utcnow().replace(microsecond=0).isoformat() + 'Z',
+                    'core:frequency': center,
+                    'core:sample_start': 0
+                }
+            ]
+        }
+
+        with open(args.sigmf_meta_filename, 'w') as outfile:
+            json.dump(data, outfile, indent=4)
+
     if args.raw_capture_filename is not None:
         import json
         import datetime