diff --git a/src/tscut/coarse.py b/src/tscut/coarse.py
new file mode 100644
index 0000000..0e280a5
--- /dev/null
+++ b/src/tscut/coarse.py
@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (C) 2026 Frédéric Tronel
+
+import logging
+from typing import IO
+
+from tscut.tools.mkvtoolnix import (
+    extract_mkv_part,
+)
+
+logger = logging.getLogger(__name__)
+
+
+
+
+
+# TODO: finish this procedure
+def do_coarse_processing(ffmpeg_path:str, ffprobe_path:str, mkvmerge_path:str,
+                         input_file: IO[bytes], begin, end, nb_frames, framerate,
+                         files_prefix, streams, width, height, temporaries, dump_mem_fd) -> None:
+    # pylint: disable=W0613
+    logger = logging.getLogger(__name__)
+
+    # Internal video with all streams (video, audio and subtitles)
+    internal_mkv_name = f'{files_prefix}.mkv'
+
+    try:
+        internal_mkv = open(internal_mkv_name, 'wb+')
+    except OSError:
+        logger.error('Impossible to create file: %s', internal_mkv_name)
+        exit(-1)
+
+    # Extract internal part of MKV
+    extract_mkv_part(mkvmerge_path=mkvmerge_path, input_file=input_file, output_file=internal_mkv,
+                     begin=begin, end=end)
+
+    temporaries.append(internal_mkv)