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README.md

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+## id3chap
+
+A command-line tool for adding ID3 chapters to an MP3 file.
+
+### Usage
+
+    id3chap file.mp3 0 "chapter 1" 123 "chapter 2" 456 "chapter 3"
+
+The first argument is the path to the MP3 file, then pairs of arguments each containing
+a start time in seconds, and the chapter title.
+
+It is assumed that each chapter ends where the next one begins, and that the final chapter
+ends at the last millisecond of the file (as defined in its `TLEN` ID3 frame).
+
+Changes to the ID3 tag in the MP3 file are written out in-place.
+
+### License
+
+3-clause BSD