youtube audio prep

27 Dec 2024

Recently, I got interested in listening to history lectures on Youtube. Since many of the lectures are long and the video part is usually unimportant, I start to conceive a more portable format of lecture, which is ad-free and does not require Internet access. This leads to the idea of downloading the videos and converting them to audios came up.

Batch download

I started with websites like y2mate. They worked, but when I want to download a series of videos, they are not satisfactory because I have to wait for the first one to complete before starting the second one. Ideally, I should be able to make a list of videos I want to download and to have a software keep downloading according to the list – to enable batch download.

This led me to the software yt-dlp. It is a command line tool which download Youtube videos with a one-line command. The command typically looks like

yt-dlp [--options] URL

Batch download is simple:

create a .bat file
in a text editor, repeat the command with different URLs

# batch-download.bat

yt-dlp [--options] URL1
yt-dlp [--options] URL2
yt-dlp [--options] URL3
yt-dlp [--options] URL4

When execute the batch-download.bat file in a terminal, all the videos will be downloaded.

Audio

By default, yt-dlp downlaods videos. To download audio only, the --options need to be configured correctly. Here’s an example:

yt-dlp -f bestaudio --extract-audio --audio-format mp3 --audio-quality 0 URL

Member-only content

Some videos require subscription to the channel to view/download. To make yt-dlp authorized to download member-only content, we need to pass the cookies of the browser as an argument in the command. First, download the cookies using the chrome extension Get cookies.txt LOCALLY. The cookies txt file looks like this:

# Netscape HTTP Cookie File
# http://curl.haxx.se/rfc/cookie_spec.html
# This is a generated file!  Do not edit.

.youtube.com	TRUE	/	TRUE	1751208406	LOGIN_INFO	AFmmF2swRAIgbOeLIrLuxRY6YyAL9bauDQXDbVxJdIt_xa1t7RM-HjwCIAM1viLjg9sWq_Qc4y1_mPQZYFW6Jfx_7FM_X2gkoblx:QUQ3MjNmek1nd0hvUGFGdDRoRXEyRWNudW1XdEh6Z3Rhb1VNTnhCdE0zRXozSzRjZk5qOGtvX24wQk1DTUlDRnJET055cHN0SW9RUlByZUpJOE9yaTdvRnhOUENUMHFxTTg0Wm5zR2RIU25qbkhfRHVYd0hpZmpmOEgyaS0xR1RtWDhfa2VOZGQ4ZDlTTmZTd0RTeng3WDFXZzZVSkZkaUJR
.youtube.com	TRUE	/	FALSE	1769051874	HSID	A-iCb3kDOJnG5AD6S
.youtube.com	TRUE	/	TRUE	1769051874	SSID	AV_KZaPZG2UsQDFu4
.youtube.com	TRUE	/	FALSE	1769051874	APISID	qlZgHSCBNqOiSYjk/AbEDyy7SdG_vUo0EM
.youtube.com	TRUE	/	TRUE	1769051874	SAPISID	z9PnNR9VFR5N3Jf4/AgcS_3AQA9DbPWNeU
.youtube.com	TRUE	/	TRUE	1769051874	__Secure-1PAPISID	z9PnNR9VFR5N3Jf4/AgcS_3AQA9DbPWNeU
.youtube.com	TRUE	/	TRUE	1769051874	__Secure-3PAPISID	z9PnNR9VFR5N3Jf4/AgcS_3AQA9DbPWNeU

Then, put this .txt file in the same directory as the .bat file and the yt-dlp executable. Lastly, add the cookies argument to the command. The final command looks like:

yt-dlp -f bestaudio --extract-audio --audio-format mp3 --audio-quality 0 URL --cookies cookies.txt

Concatenate audios

A complete long lecture are usually divided into small segments for easier browsing on Youtube. For listening, I’d prefer to group the same topic in one audio file. A good way to concatenate audio files is the linux software sox. First, put the audio files from one lecture into a same master folder. Then, run WSL, navigate to this folder (/mnt/c/Users/...), run the following command:

$ sox *.mp3 out.mp3

This creates an all-in-one lecture. Happy learning!