https://blog.faceutil.com/2017/03/19/video-cache-view-%eb%8f%99%ec%98%81%ec%83%81-%ed%8c%8c%ec%9d%bc%ec%9d%84-%eb%94%b0%eb%a1%9c-%ec%a0%80%ec%9e%a5%ed%95%98%ec%9e%90-%cf%86/