# Parsing extra metadata **URL:** \ **Category:** GNU Radio\ **Created:** [August 19, 2014, 10:15pm UTC](https://www.ruby-forum.com/t/parsing-extra-metadata/231623 "2014-08-19T22:15:01Z")\ **Posts on this page:** 4\ **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:** [August 19, 2014, 10:15pm UTC](https://www.ruby-forum.com/t/parsing-extra-metadata/231623/1 "2014-08-19T22:15:01Z")
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](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 ---
**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\ **Post date:** [August 22, 2014, 12:05am UTC](https://www.ruby-forum.com/t/parsing-extra-metadata/231623/2 "2014-08-22T00:05:00Z")
On Tue, Aug 19, 2014 at 3:13 PM, Daniel M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ``` > # add some extra meta data > > ``` > > self.blocks\_file\_meta\_sink\_0.set\_unbuffered(False) > p\_extra = parse\_file\_metadata.parse\_extra\_dict(pmt\_dict,info,True) Dan, What happens when you run gr\_read\_metadata on the file that’s created? Does that show your extra header info? Tom ---
**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\ **Post date:** [August 22, 2014, 12:17am UTC](https://www.ruby-forum.com/t/parsing-extra-metadata/231623/3 "2014-08-22T00:17:47Z")
Hi Tom, Thanks for looking at this. The answer is “yes,” as can be seen from the output below. The rx\_freq field is not something that I added. I did add the “dumm” field, however. Sincerely, Dan Marlow marlow@phy-gr2:~/pulsar/DAQ$ gr\_read\_file\_metadata meta\_test.dat.hdr HEADER 0 Version Number: 0 Sample Rate: 4000000.00 sps Seconds: 0.184295 Item size: 4 Data Type: float (5) Complex? False Header Length: 189 bytes Extra Length: 40 Extra Header? True Size of Data: 65536 bytes 16384 items Extra Header: rx\_freq: 1.2e+09 dumm: 1408561917746092 ---
**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\ **Post date:** [August 22, 2014, 1:19am UTC](https://www.ruby-forum.com/t/parsing-extra-metadata/231623/4 "2014-08-22T01:19:53Z")
On Thu, Aug 21, 2014 at 6:16 PM, Daniel M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > HEADER 0 > 16384 items > > Extra Header: > rx\_freq: > 1.2e+09 > dumm: > 1408561917746092 Ok, so that’s good. Looks like the basic concept is working fine, then. The rx\_freq field is coming from the USRP. The UHD sends tags with information about the settings, which get stored in the metadata files. If you change the frequency, it’ll generate another tag for you. It looks like you should look into the gr\_read\_file\_meatadata app to see how it’s using the parse\_metadata. That might clue you into what’s going wrong in your project. Tom