added instructions to use alignment tool to README.md

README.md

@@ -1,3 +1,18 @@
-# videographer
+# Videographer
 
 [![Build and Test](https://github.com/neri14/videographer/actions/workflows/build-and-test.yml/badge.svg)](https://github.com/neri14/videographer/actions/workflows/build-and-test.yml)
+
+
+## Alignment Tool
+
+Python alignment tool is located in tools/alignment.
+
+Basic usage based on speed visible on video:
+
+1. Create and enter virtualenv
+1. Install requirements from requirements.txt
+1. determine rough clip ```START``` and ```DURATION``` that will havevisible changes in speed on bike computer (within first 30s of FIT file track) 
+1. run ```python align.py -b <START> -t <DURATION> path_to_fit_file.fit path_to_video.mp4``` to generate alignment clip
+1. open video with your favorite video player and find exact frame at which speed changes
+1. locate data frame with same speed change in alignment data and remember the ```OFFSET```
+1. use that ```OFFSET``` as input for main application to align the overlay