极光IM 自定义消息 语音信息local_path

大家好,我的项目里面里面需要用到极光IM的自定义消息,并且是语音消息,消息如下

{_id=2, messageId=218889010, direct=receive, status=receive_success, content={"format":"amr","media_id":"qiniu/file/j/EE4DADF23CAAE051E12C2D33FEF3A5C9","fsize":2206,"duration":2,"media_crc32":80757284,"extras":{}}, version=1, fromName='null', contentType=custom, contentTypesString='custom', createTimeInMillis=1484102913852, targetType=group, targetID='19166609', targetName='', fromType='user', fromID=tongben, notification=null}

问题:我应该如何下载音频并保存在本地?