# INFO: Detected an invalid packet at item INFO: Parser returned #f **URL:** \ **Category:** GNU Radio\ **Created:** [January 29, 2015, 1:38pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993 "2015-01-29T13:38:46Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [January 29, 2015, 1:38pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/1 "2015-01-29T13:38:46Z")
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 ---
**Author:** ![zszszs](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/5fc32e/32.png) [@zszszs](https://www.ruby-forum.com/u/zszszs)\ **Post date:** [January 29, 2015, 1:45pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/2 "2015-01-29T13:45:38Z")
Hi, On 01/29/2015 01:03 PM, zs wrote: > 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? ~/src/gnuradio \>\> ack-grep -C 3 “an invalid packet” gr-digital/lib/packet\_headerparser\_b\_impl.cc 80- ); 81- 82- if (!d\_header\_formatter-\>header\_parser(in, tags)) { 83: GR\_LOG\_INFO(d\_logger, boost::format(“Detected an invalid packet at item %1%”) % nitems\_read(0)); 84- message\_port\_pub(msg\_port\_id, pmt::PMT\_F); 85- } else { 86- pmt::pmt\_t dict(pmt::make\_dict()); I guess your packet header is corrupt. Best, Bastian ---
**Author:** ![zszszs](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/5fc32e/32.png) [@zszszs](https://www.ruby-forum.com/u/zszszs)\ **Post date:** [January 29, 2015, 3:45pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/3 "2015-01-29T15:45:38Z")
Hi Bastian: Thank you so much for your kindly reply.Can you tell me,for general,in which circumstance,the packet header maybe corrupt? Thank you so much. Best regards, zs ---
**Author:** ![zszszs](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/5fc32e/32.png) [@zszszs](https://www.ruby-forum.com/u/zszszs)\ **Post date:** [January 29, 2015, 5:44pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/4 "2015-01-29T17:44:37Z")
Hi, On 01/29/2015 03:13 PM, zs wrote: > Can you tell me,for general,in which circumstance,the packet header maybe > corrupt? This is very hard to tell since I don’t know what you are doing. I guess you use a header\_formatter in your flow graph and (for whatever reason) its header\_parse method returns false. For example with the default header it looks like this happens if the CRC is not correct > ---
**Author:** ![zszszs](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/5fc32e/32.png) [@zszszs](https://www.ruby-forum.com/u/zszszs)\ **Post date:** [January 30, 2015, 2:03pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/5 "2015-01-30T14:03:08Z")
Hi Bastian: Thank you so much.I use the ofdm example,and I think maybe the crc is wrong as you said,thank you. Can you give me some advices to avoid these warning?Thank you so much. Best regards, zs ---
**Author:** ![zszszs](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/5fc32e/32.png) [@zszszs](https://www.ruby-forum.com/u/zszszs)\ **Post date:** [January 30, 2015, 3:08am UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/6 "2015-01-30T03:08:44Z")
Hi Bastian: Thank you so much.I use the ofdm example,and I think maybe the crc is wrong as you said,thank you. Best regards, zs ---
**Author:** ![zszszs](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/5fc32e/32.png) [@zszszs](https://www.ruby-forum.com/u/zszszs)\ **Post date:** [January 31, 2015, 12:50pm UTC](https://www.ruby-forum.com/t/info-detected-an-invalid-packet-at-item-info-parser-returned-f/233993/7 "2015-01-31T12:50:32Z")
> On 30 Jan 2015, at 14:00, zs [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > Hi Bastian: > Thank you so much.I use the ofdm example,and I think maybe the > crc is wrong as you said,thank you. > Can you give me some advices to avoid these warning?Thank you > so much. The fact that your CRC is not correct just means that _something_ does not work. This can have a lot of reasons. For example you could try different gain settings. Also assert that the samples that you stream to your USRP are in the interval [-1, 1]. If that doesn’t solve your problem you can debug your flow graph with graphical sinks and check if the signal looks as expected. > > This is very hard to tell since I don’t know what you are doing. I guess > > > > > > > this problem more details?Why will have this error/warning? > > > > > 85- } else { – Dipl.-Inform. Bastian B. Distributed Embedded Systems Group University of Paderborn, Germany > **[Home](https://www.bastibl.net/)** > > I'm Bastian Bloessl, a Research Group Leader at the Secure Mobile Networking Lab, TU Darmstadt. Checkout my blog, projects, publications, and resume; or connect on Github, Twitter, YouTube, or Facebook.