>>748関連備忘録
グループ通話もSIPベース？p2pかと思ってた
https://vezloaforce.jp/takehiro/216/
https://xtech.nikkei.com/it/article/COLUMN/20121108/436124/
https://engineering.linecorp.com/ja/blog/line-group-call-conference-calls-with-up-to-200-people/