ffmpeg chapters creation

chapters-ffmpeg.py

# copy of https://ikyle.me/blog/2020/add-mp4-chapters-ffmpeg

import re

chapters = list()

with open('chapters.txt', 'r') as f:
   for line in f:
      if not line.strip():
         continue
      
      x = re.match(r"(\d):(\d{2}):(\d{2}) (.*)", line)
      hrs = int(x.group(1))
      mins = int(x.group(2))
      secs = int(x.group(3))
      title = x.group(4)

      minutes = (hrs * 60) + mins
      seconds = secs + (minutes * 60)
      timestamp = (seconds * 1000)
      chap = {
         "title": title,
         "startTime": timestamp
      }
      chapters.append(chap)

text = ""

for i in range(len(chapters)-1):
   chap = chapters[i]
   title = chap['title']
   start = chap['startTime']
   end = chapters[i+1]['startTime']-1
   text += f"""
[CHAPTER]
TIMEBASE=1/1000
START={start}
END={end}
title={title}
"""


with open("FFMETADATAFILE", "a") as myfile:
    myfile.write(text)

chapters.txt

0:01:41 Chapter 1
0:02:00 Another Chapter
0:02:11 Whatever Chapter
0:02:25 Extra Chapter
0:02:42 Credits
0:05:42 needed to avoid off by one, time should be end of video

FFMETADATAFILE.example

;FFMETADATA1
major_brand=mp42
minor_version=0
compatible_brands=mp42mp41
title=Sharks Group Video Film.mp4
comment=some comment
encoder=Lavf58.76.100

[CHAPTER]
TIMEBASE=1/1000
START=101000
END=119999
title=Chapter 1

[CHAPTER]
TIMEBASE=1/1000
START=120000
END=130999
title=Another Chapter

[CHAPTER]
TIMEBASE=1/1000
START=131000
END=144999
title=Another Chapter

run.sh

# Get existing video metadata
ffmpeg -i INPUT.mp4 -f ffmetadata FFMETADATAFILE

# make sure no CHAPTERS in FFMETADATAFILE
python3 chapters-ffmpeg.py

ffmpeg -i INPUT.mp4 -i FFMETADATAFILE -map 0 -map_metadata 1 -codec copy OUTPUT.mp4