Uint8Array. can be empty if it's failed audio js
if it's single file u set json data {"downloadType":"web_api_get_all_generating_urls_data_from_iframe","itag":251,"minChunkSize":5295308,"fileSize":"xxx"} if it's error u set only downloadType (1=web_api_get_all_generating_urls_data_from_iframe)
video translation audio info. Used separated