diff --git a/src/msp.rs b/src/msp.rs
index a393311..b553f04 100644
--- a/src/msp.rs
+++ b/src/msp.rs
@@ -6,6 +6,7 @@ autoerr::create_error_v1!(
     name(Error, "BinMsp"),
     enum variants {
         PrebinnedPartitioningInvalid,
+        BadDv1(u32),
     },
 );
 
@@ -25,7 +26,28 @@ impl fmt::Display for PrebinnedPartitioning {
     }
 }
 
+#[derive(Debug, Clone)]
+pub struct QuoRem {
+    dv1: u32,
+    dv2: u32,
+    quo: u32,
+    rem: u32,
+}
+
 impl PrebinnedPartitioning {
+    pub fn from_dv1_abs(dv1: u32) -> Result<Self, Error> {
+        use PrebinnedPartitioning::*;
+        match dv1 {
+            0x104 => Ok(Sec1),
+            0xa04 => Ok(Sec10),
+            0x105 => Ok(Min1),
+            0xa05 => Ok(Min10),
+            0x106 => Ok(Hour1),
+            0x107 => Ok(Day1),
+            _ => Err(Error::BadDv1(dv1)),
+        }
+    }
+
     pub fn bin_len(&self) -> DtMs {
         use PrebinnedPartitioning::*;
         match self {
@@ -38,45 +60,52 @@ impl PrebinnedPartitioning {
         }
     }
 
-    pub fn msp_div(&self) -> DtMs {
+    pub fn bin_len_dv1_abs(&self) -> u32 {
         use PrebinnedPartitioning::*;
-        if true {
-            match self {
-                Sec1 => DtMs::from_ms_u64(1000 * 60 * 20),
-                Sec10 => DtMs::from_ms_u64(1000 * 60 * 60 * 2),
-                Min1 => DtMs::from_ms_u64(1000 * 60 * 60 * 12),
-                Min10 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 7),
-                Hour1 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 40),
-                Day1 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 800),
-            }
-        } else {
-            match self {
-                Sec1 => DtMs::from_ms_u64(1000 * 60 * 10),
-                Sec10 => DtMs::from_ms_u64(1000 * 60 * 60 * 2),
-                Min1 => DtMs::from_ms_u64(1000 * 60 * 60 * 8),
-                Min10 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 4),
-                Hour1 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 28),
-                Day1 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 400),
-            }
+        match self {
+            Sec1 => 0x100 | 0x04,
+            Sec10 => 0xa00 | 0x04,
+            Min1 => 0x100 | 0x05,
+            Min10 => 0xa00 | 0x05,
+            Hour1 => 0x100 | 0x06,
+            Day1 => 0x100 | 0x07,
         }
     }
 
-    pub fn quo_rem(&self, val: TsMs) -> (u64, u32, u32, u32) {
-        let dv1 = self.msp_div().ms();
+    pub fn batch_len(&self) -> u32 {
+        use PrebinnedPartitioning::*;
+        match self {
+            Sec1 => 1200,
+            Sec10 => 720,
+            Min1 => 720,
+            Min10 => 1008,
+            Hour1 => 960,
+            Day1 => 800,
+        }
+    }
+
+    pub fn batch_dt(&self) -> DtMs {
+        self.bin_len().mul(self.batch_len() as u64)
+    }
+
+    // how to decide if we use multi-level index?
+    // it is "this", the bin-len itself.
+    pub fn quo_rem_l1(&self, val: TsMs) -> (QuoRem, DtMs) {
+        let divms = self.batch_dt().ms();
+        let dv1 = self.bin_len_dv1_abs();
         let dv2 = self.bin_len().ms();
         let valms = val.ms();
-        let quo = valms / dv1;
-        let rrr = valms % dv1;
+        let quo = valms / divms;
+        let rrr = valms % divms;
         let rem = rrr / dv2;
-        (quo, rem as u32, dv1 as u32, dv2 as u32)
-    }
-
-    pub fn off_max(&self) -> u32 {
-        self.msp_div().ms() as u32 / self.bin_len().ms() as u32
-    }
-
-    pub fn clamp_off(&self, off: u32) -> u32 {
-        self.off_max().min(off)
+        let rr2 = rrr % dv2;
+        let quo_rem = QuoRem {
+            dv1,
+            dv2: dv2 as u32,
+            quo: quo as u32,
+            rem: rem as u32,
+        };
+        (quo_rem, DtMs::from_ms_u64(rr2))
     }
 
     pub fn uses_index_hour1(&self) -> bool {
@@ -114,3 +143,26 @@ impl TryFrom<DtMs> for PrebinnedPartitioning {
         }
     }
 }
+
+#[test]
+fn test_quo_rem_00() {
+    let ts1 = TsMs::from_ms_u64(1000 * 60 * 60 * 24 * 817 + 17784239);
+    let (qr, dt) = PrebinnedPartitioning::Day1.quo_rem_l1(ts1);
+    // eprintln!("{:?}  {:?}", qr, dt);
+    assert_eq!(qr.dv1, 0x107);
+    assert_eq!(qr.quo, 1);
+    assert_eq!(qr.rem, 17);
+    assert_eq!(dt, DtMs::from_ms_u64(17784239));
+}
+
+#[test]
+fn test_quo_rem_01() {
+    let ts1 = TsMs::from_ms_u64(1000 * 60 * 60 * 24 * 817 + 17784239);
+    let (qr, dt) = PrebinnedPartitioning::Day1.quo_rem_l1(ts1);
+    let pbp = PrebinnedPartitioning::from_dv1_abs(qr.dv1).unwrap();
+    eprintln!("{:?}", pbp);
+    let tsms = pbp.batch_dt().ms() * qr.quo as u64 + pbp.bin_len().ms() * qr.rem as u64 + dt.ms();
+    eprintln!("{:?}", tsms);
+    eprintln!("{:?}", ts1.ms());
+    panic!()
+}