[Discuss-gnuradio] INFO: Detected an invalid packet at item INFO: Parser returned #f

[zs]

Hi all:
         Thank you in advance.I have searched the question"INFO: Detected an invalid packet at item INFO: Parser returned #f".
The answer may be "RF settings are distorting your signal" or others.I want to ask a question.Which block in gnuradio give us this hint.Where is the source code of the block?And have someone can help me to explain this problem more details?Why will have this error/warning?
        Thank you.
Best regards,
zs