[Discuss-gnuradio] Parsing extra metadata

[Daniel Marlow]

Hello,

   I am trying to add some extra information to the standard metadata file header.    

   Following the information posted on http://gnuradio.org/doc/doxygen/page_metadata.html , I am able to write and read the standard metadata.    I have attempted to add extra metadata with the following lines in my flowgraph:

                # add some extra meta data

key = pmt.pmt_intern("dummy")

val = pmt.pmt_from_long(77) 

extras = pmt.pmt_make_dict()

extras = pmt.pmt_dict_add(extras, key, val)

extras_str = pmt.pmt_serialize_str(extras)

                nItems = 1024*size

self.blocks_file_meta_sink_0 =  blocks.file_meta_sink(gr.sizeof_float*1,"./meta_test.dat",

  samp_rate, 1, blocks.GR_FILE_FLOAT, False, nItems, extras_str, True)

self.blocks_file_meta_sink_0.set_unbuffered(False)

  I think that the writing is going OK, since the length of the header increases by a reasonable amount and a Unix hexdump indicates that the "dummy" data is present.   However, I am stuck when it comes to getting at the extra data using the parse_file_metadata functions.  In particular, when I try to read the data using:

        cHeader = c[0:185]   # character array read from file 

    pmt_dict = pmt.pmt_deserialize_str(cHeader) 

    p = parse_file_metadata.parse_header(pmt_dict,False)

    p_extra = parse_file_metadata.parse_extra_dict(pmt_dict,info,True)

    

The first parse_file_metadata line successfully provides the standard metadata, but the second parse_file_metadata does not provide the extra "dummy" data.   I suspect that it has to do with my poor understanding of what should go in the info argument.

Any help would be greatly appreciated.

Sincerely,

Dan Marlow