def METHOD_NAME(inps):
    """Get auxliary files' default filename."""
    ts_dir = os.path.dirname(inps.ts_file)
    ts_prefix = os.path.basename(inps.ts_file).split('timeseries')[0]
    fbase = os.path.join(ts_dir, ts_prefix)
    inps.vel_file  = inps.vel_file  if inps.vel_file  else f'{fbase}velocity.h5'
    inps.tcoh_file = inps.tcoh_file if inps.tcoh_file else f'{fbase}temporalCoherence.h5'
    inps.mask_file = inps.mask_file if inps.mask_file else f'{fbase}maskTempCoh.h5'
    return inps