This posts introduces the way to download Chinese songs from a playlist on youtube and process titles of songs.
I use youtube-dl to download all songs from a playlist (replace the youtube link with your own, make sure the playlist is public):
youtube-dl -i --yes-playlist -x --audio-format mp3 -o "%(title)s.%(ext)s" --audio-quality 0 "https://www.youtube.com/watch?v=4V3hxNyiwaA&index=1&list=PL-VzXmWCFX7iz_hxy6Xb-JXZFs4GGKMdG"
Update 2024-1-26:
Youtube-dll is no longer maintained and you should install yt-dlp instead by `brew install yt-dlp`. Once yt-dlp is installed, you can still use the command above (starting with youtube-dl) to download songs.
There could be many titles written in traditional Chinese characters. Since I am more comfortable with reading in simplified Chinese, I use a tool to batch convert traditional Chinese to simplified Chinese: https://www.dropbox.com/sh/qowqk15kpt7olak/AAB4pb3EDvzXVbmP-JMZLsIfa?dl=0
Update 2020.4
If you see Chinese not properly displayed in the tool for batch converting file names, you need to configure language settings: https://www.zhihu.com/question/34761050/answer/140114217