怎样下载视频到电脑上为mp4(如何下载优酷视频以后直接转换成格式mp4格式)

{"rich_content":{"text":"","spans":null},"video":{"vid":"v028b0b70000br0g8qm8qblds6dr33vg","duration":53.018,"width":1280,"height":720,"file_size":8074545,"thumb":{"web_uri":"tos-cn-p-0000/cfa612a9535341e89a7d10dd56ddbd94","width":640,"height":360,"image_type":null,"mimetype":null,"encrypt_web_uri":null,"secret_key":null,"encrypt_algorithm":null,"extra":null},"video_size":{"high":{"duration":53.018,"file_size":2342601,"w":854,"h":480},"normal":{"duration":53.018,"file_size":1784529,"w":640,"h":360},"ultra":{"duration":53.018,"file_size":3697138,"w":1280,"h":720}},"is_encrypted":null,"md5":"c095b80776049e9d44bab5e2929c39c2","tos_key":null,"secret_key":null,"encrypt_algorithm":null,"extra":null}}