前台播报正常，后台播报遇到问题

[dreamahui]

提示：Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSLocalizedFailureReason=An unknown error occurred (-16980), NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x100b50a50 {Error Domain=NSOSStatusErrorDomain Code=-16980 "(null)"}}