File_meta_sink block in grc producing incorrect size of data and items in output file

[tonycolo]

What happened?

The file written by file meta sink block produces output that is incorrect in terms of size of items / nitems and bytes.

===Data segment 0 ===
Version Number: 0
Sample Rate: 32000.00 sps
Seconds: 0.0000000000000000
Item size: 4
Data Type: float (5)
Complex? False
Header Length: 167 bytes
Extra Length:  18
Extra Header?  True
Size of Data: 0 bytes
              0.0 items
Initial: 3
{'rx_rate': 32000.0, 'rx_time_secs': 0, 'rx_time_fracs': 0.0, 'rx_time': 0.0, 'size': 4, 'type': 'float', 'cplx': False, 'hdr_len': 167, 'extra_len': 18, 'has_extra': True, 'nitems': 0.0, 'nbytes': 0, 'Initial': 3}
1024 data elements read

===Data segment 1 ===
Traceback (most recent call last):
  File "printbinary.py", line 25, in <module>
    header = pmt.deserialize_str(header_str)
RuntimeError: pmt::deserialize: malformed input stream, tag value = : 31

I manually calculated 1024 data elements and read those in, but reading the next segment produces the runtime error above. This might be a clue.
The file that is written is far larger than the metadata header section.

System Information

Windows 10
RadioConda

GNU Radio Version

3.9 (maint-3.9)

Specific Version

3.9.5.0

Steps to Reproduce the Problem

1. Run example flowgraph
2. Run command line python example as seen in Wiki entry for File Meta Sink.

Note that per this issue, I had to add an " import pmt" to the .yml definition for File Meta Sink for this block to work at all in GRC.

Relevant log output

No response

[marcusmueller]

Hi, thanks for the output file! I was super stocked to get the flow graph that produced it, but I only find a link to the data file – could you share the flow graph with us?

[tonycolo]

Demo flow graph

[SDRnoob]

I'm totally new to this ordeal. If you're using an sdr source, it may be that the sdr is sending 'tags' into the signal. In my case, at each overflow, a tag was generated, causing my files to break off unexpectedly, but oddly enough sometimes have more data than they should have. You can check by adding in a tag debug to print them out, or a tag gate to block them all together.