A better README.

README.md

@@ -1,3 +1,26 @@
-# removeads
+# Goal of the script
 
-Remove ads from TV recordings with optimal cuts.
+Remove ads from TV recordings with optimal cuts with single video frame precision.
+
+When I record a movie on TV, I sometimes wish to archive the movie on my NAS.
+In that case, I want to remove (at least) the beginning and the end of the recording
+if the movie was broadcast on a advertisment free channel, or even worse I may
+have to split it in numerous parts so as to remove the advertisments.
+And I do not want to reencode the entire movie since it's a really slow process (on my NAS)
+and the movie is already broadcast using H264 (DVB-T).
+
+Doing this by hand is really painful, because most tools like ffmpeg, or mkvmerge are only
+able to cut a movie (without reencoding) at a boundary within the video stream that corresponds
+to a reference frame (so called I-frames). These frames are only present roughly every 10-20 frames
+which corresponds to quite long duration (in the order of a second).
+
+I really want to cut the movie with a better precision. So I have written a Python script
+that leverages _ffmpeg_, _ffprobe_ and _mkvmerge_ to do the job with the required precision.
+
+# Parameters
+
+# How does it work ?
+
+# How to determine where to cuts
+
+Use `mpv --osd-fractions --osd-level=3 ./movie.ts`