How to download chapters of a youtube video as separate video files?
A New YouTube Feature
Youtube recently enabled the option to add chapters in YouTube videos.
This is done by simply adding the chapter timestamps (start time) in the description of the video.
Related Topics
Using youtube-dl we can
download a portion of a YouTube video by providing the
start timeandduration.
extract description of a YouTube video as
.descriptionfiles.
QUESTION
Is there a single command to download chapters of a youtube video as separate video files without providing the start time and duration rather it automatically extracts the timestamps from the .description?
Solution 1:
You can't do this directly. I have written a Python script which will download the whole file, process the description file and then split the downloaded file into it's component chapters.
Usage - if you save this into a file called "yt_chapters.py" then run
yt_chapters.py --split "https://www.youtube.com/watch?v=m5lp8S-YgrQ"
You can pass multiple download links and it will loop through the list.
The chapter record will be added to the original downloaded MP4.
Requirements: youtubedl, ffmpeg and MP4Box (GPAC). If you don't want to keep the original MP4, or if you don't care about it having the chapters, you can comment out that section. youtubedl and ffmpeg should be in your system path or else change the code below to include the full path to the executables.
#! /usr/bin/env python
# -*- coding: utf-8 -*-
import subprocess, os, argparse, datetime, re, sys
def get_source_name(download_source:str)->str:
# Get the expected filename in order to process everything down the line
result = subprocess.run(["youtube-dl", "--get-filename",
"-o", "%(title)s", download_source],
capture_output=True, encoding='UTF8')
return result.stdout.rstrip('\n')
def get_best_mp4_single_file(download_source:str, description_file:str,
fix_required:bool=False)->list:
# Download the file as mp4 (in order to use MP4)
subprocess.run(["youtube-dl", "--write-description", "-f",
"bestvideo[ext=mp4]+bestaudio[ext=m4a]/mp4",
"-o", "%(title)s.%(ext)s", link_to_download])
if fix_required:
input("Fix the description file to have the chapters "
"on their own lines in the format timecode name "
"and then press Enter to continue...")
return read_description_file(description_file=description_file)
def get_worst_mp4_single_file(download_source:str, description_file:str,
fix_required:bool=False)->list:
# Download the file as mp4 (in order to use MP4)
subprocess.run(["youtube-dl", "--write-description", "-f",
"worstvideo[ext=mp4]+worstaudio[ext=m4a]/mp4",
"-o", "%(title)s.%(ext)s", link_to_download])
if fix_required:
input("Fix the description file to have the chapters "
"on their own lines in the format timecode name "
"and then press Enter to continue...")
return read_description_file(description_file=description_file)
def add_chapters_to_mp4(chapter_file_name:str, name_for_download:str)->None:
# Use MP4Box to mux the chapter file with the mp4
subprocess.run(["MP4Box", "-chap", chapter_file_name, name_for_download])
def read_description_file(description_file:str)->list:
# Read the description file
# Split into time and chapter name
list_of_chapters = []
with open(description_file, 'r') as f:
# only increment chapter number on a chapter line
# chapter lines start with timecode
line_counter = 1
for line in f:
result = re.search(r"\(?(\d?[:]?\d+[:]\d+)\)?", line)
try:
# result = re.search("\(?(\d+[:]\d+[:]\d+)\)?", line)
time_count = datetime.datetime.strptime(result.group(1), '%H:%M:%S')
except:
try:
# result = re.search("\(?(\d+[:]\d+)\)?", line)
time_count = datetime.datetime.strptime(result.group(1), '%M:%S')
except:
continue
chap_name = line.replace(result.group(0),"").rstrip(' :\n')
chap_pos = datetime.datetime.strftime(time_count, '%H:%M:%S')
list_of_chapters.append((str(line_counter).zfill(2), chap_pos, chap_name))
line_counter += 1
return list_of_chapters
def write_chapters_file(chapter_file:str, chapter_list:tuple)->None:
#open(chapter_file, 'w').close()
# Write out the chapter file based on simple MP4 format (OGM)
with open(chapter_file, 'w') as fo:
for current_chapter in chapter_list:
fo.write(f'CHAPTER{current_chapter[0]}='
f'{current_chapter[1]}\n'
f'CHAPTER{current_chapter[0]}NAME='
f'{current_chapter[2]}\n')
def split_mp4(chapters:list, download_filename:str, download_name:str)->None:
# current_duration = subprocess.run(['ffprobe', '-i', download_filename,
# '-show_entries', 'format=duration',
# '-v', 'quiet', '-of', 'csv="p=0"'],
# capture_output=True, encoding='UTF8')
current_duration_pretext = subprocess.run(['ffprobe', '-i', download_filename,
'-show_entries', 'format=duration',
'-v', 'quiet'],
capture_output=True, encoding='UTF8')
current_duration = float(current_duration_pretext.stdout[18:-13])
m, s = divmod(current_duration, 60)
h, m = divmod(m, 60)
current_dur = ':'.join([str(int(h)),str(int(m)),str(s)])
for current_index, current_chapter in enumerate(chapters):
# current_chapter will be a tuple: position, timecode, name
next_index = current_index + 1
start_time = current_chapter[1]
try:
end_time = chapters[next_index][1]
except:
end_time = current_dur
output_name = f'{download_name} - ({current_chapter[2]}).mp4'
subprocess.run(["ffmpeg", "-ss", start_time, "-to", end_time,
"-i", download_filename, "-acodec", "copy",
"-vcodec", "copy", output_name])
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='Download Youtube videos with chapters')
parser.add_argument('links', metavar='N', type=str, nargs='+',
help='List of links to download')
parser.add_argument("--split", help="Split chapters into individual files",
action="store_true")
parser.add_argument("--test", help="Download worst version to speed up testing",
action="store_true")
parser.add_argument("--fix", help="Pause to allow manual correction of the description file",
action="store_true")
args = parser.parse_args()
# print(args.links)
for link_to_download in args.links:
download_name = get_source_name(download_source=link_to_download)
download_filename = f'{download_name}.mp4'
description_file = f'{download_name}.description'
chapter_file = f'{download_name}_chapter.txt'
if not args.test:
chapters = get_best_mp4_single_file(download_source=link_to_download,
description_file=description_file,
fix_required=args.fix)
else:
chapters = get_worst_mp4_single_file(download_source=link_to_download,
description_file=description_file,
fix_required=args.fix)
if not chapter_file:
print("No chapters found")
sys.exit(1)
write_chapters_file(chapter_file=chapter_file, chapter_list=chapters)
if args.split:
split_mp4(chapters=chapters, download_filename=download_filename,
download_name=download_name)
add_chapters_to_mp4(chapter_file_name=chapter_file,
name_for_download=download_filename)
# Clean up the text files
os.remove(description_file)
os.remove(chapter_file)