compute_proj_ecg throws a warning

[larsoner]

I get a warning when using the default parameters for compute_proj_ecg:

/home/larsoner/.local/lib/python2.7/site-packages/mne-0.4.git-py2.7.egg/mne/filter.py:234: UserWarning: Attenuation at stop frequency 4.5Hz is only 15.1dB. Increase filter_length for higher attenuation.

I assume this has to do with the 5 Hz high-pass frequency requiring a long FIR filter.

Would it make sense to set the filter_length argument to something larger by default for compute_proj_ecg?

[larsoner]

And changing filter_length to 4096 from the default of 2048 makes it so no warning is thrown.

Any objections to changing it to 4096?

[larsoner]

Changing the default to 4096, that is.

[agramfort]

Yes go ahead !