Decimation of files with python and obspy

Question

I am trying to make a decimation to mseed format files. For now I am using this code.

import numpy as np
import matplotlib.pyplot as plt
import obspy
import sys

with open(sys.argv[1],"rb") as fh:
        fh.seek(512)
        st = obspy.read(fh)


tr = st[0]
tr_new = tr.copy()
tr_new.decimate(factor=5, strict_length=False)
tr_new.write(sys.argv[1] + ".20sps",format="mseed")

tr_filt = tr.copy()
tr_filt.filter('lowpass', freq=0.4 * tr.stats.sampling_rate / 4.0)

t = np.arange(0, tr.stats.npts / tr.stats.sampling_rate, tr.stats.delta)
t_new = np.arange(0, tr_new.stats.npts / tr_new.stats.sampling_rate,
tr_new.stats.delta)

But when I run it I get the following error.

Analizando: /home/miguel/Documentos/mseed_decimacion/HHZ.D/caig.ig.hhz.d.2018.107.0000
/usr/lib/python2.7/dist-packages/obspy/io/mseed/core.py:772: UserWarning: The encoding specified in trace.stats.mseed.encoding does not match the dtype of the data.
A suitable encoding will be chosen.
  warnings.warn(msg, UserWarning)

Answer 1

The original MiniSEED data is likely stored as integers and compressed with an integer-only compression (STEIM). This metainformation is retained with the Trace objects after reading the data. During decimation a filter is applied which results in the data being converted to floating point numbers. When you then write the data to MiniSEED at the end, ObsPy looks at the metainformation that still have the integer-only compression scheme and recognizes that it can not write the floating point data with that compression scheme. It then falls back to writing uncompressed floating point MiniSEED, so there is really nothing to worry about here. It's just a warning after all, no error.