diff options
| author | Daniel Estévez <daniel@destevez.net> | 2020-08-25 21:14:42 +0200 |
|---|---|---|
| committer | mormj <34754695+mormj@users.noreply.github.com> | 2020-10-20 12:28:36 -0400 |
| commit | 912d48596569812ddcd05539bc7086617971b65e (patch) | |
| tree | 9a0552142b6346d84fac62713cef5b2b158b71a2 /gr-blocks/python | |
| parent | a93d6c3bf2e20f3f3795fc631af33acc9ef1f187 (diff) | |
blocks: prevent losing rx_time precision in gr_read_file_metadata
The utility gr_read_file_metadata uses parse_file_metadata.parse_header()
from gr-blocks to parse and print headers in a metadata file. Currently,
the rx_time field is printed with us precision. However, the rx_time is
stored as the integer seconds of the UNIX timestamp in an uint64_t plus
a double storing the fraction of a second, so the rx_time has more
precision.
A precision on the order of 1ns is necessary for many ranging applications,
since 1us is approximately 300m of range.
This modifies parse_file_metadata.parse_header() to print rx_time with 16
decimal places, without losing precision. Aditionally, it adds "rx_time_secs"
and "rx_time_fracs" fields to the dict() return value of parse_header(), in
case they are ever needed. The "rx_time" field in this dict() is a double,
and as such it is unable to store a UNIX timestamp with 1ns precision.
Diffstat (limited to 'gr-blocks/python')
| -rw-r--r-- | gr-blocks/python/blocks/parse_file_metadata.py | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/gr-blocks/python/blocks/parse_file_metadata.py b/gr-blocks/python/blocks/parse_file_metadata.py index 5beede0e72..d98a6c6127 100644 --- a/gr-blocks/python/blocks/parse_file_metadata.py +++ b/gr-blocks/python/blocks/parse_file_metadata.py @@ -10,6 +10,7 @@ import sys +import decimal from gnuradio import gr, blocks import pmt @@ -75,12 +76,20 @@ def parse_header(p, VERBOSE=False): r = pmt.dict_ref(p, pmt.string_to_symbol("rx_time"), dump) secs = pmt.tuple_ref(r, 0) fracs = pmt.tuple_ref(r, 1) - secs = float(pmt.to_uint64(secs)) + secs = pmt.to_uint64(secs) fracs = pmt.to_double(fracs) - t = secs + fracs + t = float(secs) + fracs + info["rx_time_secs"] = secs + info["rx_time_fracs"] = fracs info["rx_time"] = t if(VERBOSE): - print("Seconds: {0:.6f}".format(t)) + # We need are going to print with ~1e-16 resolution, + # which is the precision we can expect in secs. + # The default value of precision for decimal + # is 28. The value of secs is not expected to be larger + # than 1e12, so this precision is enough. + s = decimal.Decimal(secs) + decimal.Decimal(fracs) + print("Seconds: {0:.16f}".format(s)) else: sys.stderr.write("Could not find key 'time': invalid or corrupt data file.\n") sys.exit(1) |