decode failed but no error info

[AlexAnder]

any other message can encode and code right , but one large proto struct can't when the server return the stream of pb , i use the pb.decode("packageName", stream） return the false ,and the second param (error) is "" empty string . the part of the stream is like :
�^����e M
-������nba1138"(0�:B
210.12.30.134H���$ � � � � � � � � � � � � �(�0"
��������robot266"(0�:BH��(�0*"
��������robot267"(0�:BH��(�0*"
��������robot268"(0�:BH��(�00:汉字汉字汉字汉字等等
so . why ...