diff --git a/examples/bag_info.rs b/examples/bag_info.rs
index 323a224..4d739d2 100644
--- a/examples/bag_info.rs
+++ b/examples/bag_info.rs
@@ -1,4 +1,4 @@
-use std::{convert::TryFrom, env::args, fs::File, io};
+use std::{collections::HashMap, convert::TryFrom, env::args, fs::File, io};
 
 use eyre::Context;
 use log::{error, info, trace};
@@ -7,7 +7,7 @@ use regex::Regex;
 use ros_message::{MessagePath, Msg};
 use rsbag::{
     chunk::ChunkHeader,
-    index::{BagIndex, ConnInfo},
+    index::{BagIndex, ConnInfo, IndexData},
     reader::{BagReader, MmapReader},
     Result,
 };
@@ -57,6 +57,23 @@ fn read_chunk<R: BagReader>(bag_reader: &mut R, pos: u64) -> Result<Vec<u8>> {
     Ok(data)
 }
 
+#[derive(Default, Debug)]
+struct BagInfo {
+    total_uncompressed: u64,
+    per_connection: HashMap<u32, u64>,
+}
+
+impl BagInfo {
+    fn combine(mut self, other: BagInfo) -> BagInfo {
+        self.total_uncompressed += other.total_uncompressed;
+        for (conn, count) in other.per_connection {
+            *self.per_connection.entry(conn).or_insert(0) += count;
+        }
+        self
+    }
+
+}
+
 fn main() -> Result<()> {
     color_eyre::install()?;
     env_logger::init();
@@ -91,28 +108,30 @@ fn main() -> Result<()> {
         }
     }
 
-    let total_size = index
+    let data = index
         .chunks
         .par_iter()
-        .try_fold(
-            || 0u64,
-            |total_size, chunk| -> rsbag::Result<_> {
-                let mut reader = bag_reader.clone();
-                let chunk_header = ChunkHeader::read(&mut reader, chunk.pos)?;
-                reader.skip_data()?;
+        .try_fold(BagInfo::default, |mut data, chunk| -> rsbag::Result<_> {
+            let mut reader = bag_reader.clone();
+            let chunk_header = ChunkHeader::read(&mut reader, chunk.pos)?;
+            data.total_uncompressed += chunk_header.uncompressed_size as u64;
+            reader.skip_data()?;
 
-                // let data = read_chunk(&mut bag_reader.clone(), chunk.pos)?;
-                // chunks.push(data);
-                Ok(total_size + chunk_header.uncompressed_size as u64)
-            },
-        )
-        .reduce(
-            // || Ok(Vec::new()),
-            || Ok(0),
-            |a, b| a.and_then(|a| b.map(|b| a + b)),
-        )
+            for _ in &chunk.connections {
+                let index = IndexData::read(&mut reader)?;
+                *data.per_connection.entry(index.conn_id).or_insert(0) +=
+                    index.entries.len() as u64;
+            }
+
+            // let data = read_chunk(&mut bag_reader.clone(), chunk.pos)?;
+            // chunks.push(data);
+            Ok(data)
+        })
+        .try_reduce(BagInfo::default, |a, b| Ok(a.combine(b)))
         .unwrap();
 
+    info!("bag data: {:#?}", data);
+
     // let total_size = index
     //     .chunks
     //     .par_iter()
@@ -129,7 +148,5 @@ fn main() -> Result<()> {
     //         |a, b| a.and_then(|a| b.map(|b| a + b)),
     //     )?;
 
-    info!("total uncompressed size: {}", total_size);
-
     Ok(())
 }
diff --git a/src/index.rs b/src/index.rs
index 66a0789..89d8712 100644
--- a/src/index.rs
+++ b/src/index.rs
@@ -6,7 +6,7 @@ use nom::{number::streaming::le_u32, sequence::tuple, Parser};
 
 use crate::{
     error,
-    parse::{self, Header, Op},
+    parse::{self, header::Time, Header, Op},
     reader::BagReader,
     Result,
 };
@@ -41,8 +41,8 @@ impl ConnInfo {
 #[derive(Debug)]
 pub struct ChunkInfo {
     pub pos: u64,
-    pub start_time: u64, // TODO: unpack time
-    pub end_time: u64,
+    pub start_time: Time,
+    pub end_time: Time,
     pub connections: Vec<ChunkConnection>,
 }
 
@@ -63,8 +63,8 @@ impl ChunkInfo {
         }
         Ok(ChunkInfo {
             pos: header.read_u64(b"chunk_pos")?,
-            start_time: header.read_u64(b"start_time")?,
-            end_time: header.read_u64(b"end_time")?,
+            start_time: header.read_time(b"start_time")?,
+            end_time: header.read_time(b"end_time")?,
             connections,
         })
     }
@@ -151,3 +151,49 @@ impl BagIndex {
         }
     }
 }
+
+#[derive(Debug)]
+pub struct IndexData {
+    pub conn_id: u32,
+    pub entries: Vec<IndexEntry>,
+}
+
+impl IndexData {
+    pub fn read<R: BagReader>(reader: &mut R) -> Result<Self> {
+        let header = reader.read_header_op(Op::IndexData)?;
+        if header.read_u32(b"ver")? != 1 {
+            bail!("unsupported IndexData version");
+        }
+
+        reader.read_data_length()?; // Data length not needed
+
+        let entry_count = header.read_u32(b"count")?;
+        let mut entries = Vec::with_capacity(entry_count as usize);
+        for _ in 0..entry_count {
+            let conn = IndexEntry::read(reader)?;
+            entries.push(conn);
+        }
+        Ok(IndexData {
+            conn_id: header.read_u32(b"conn")?,
+            entries,
+        })
+    }
+}
+
+#[derive(Debug)]
+pub struct IndexEntry {
+    pub time: Time,
+    pub offset: u32,
+}
+
+impl IndexEntry {
+    pub fn parse(input: parse::Input) -> parse::IResult<Self> {
+        tuple((Time::parse, le_u32))
+            .map(|(time, offset)| IndexEntry { time, offset })
+            .parse(input)
+    }
+
+    pub fn read<R: BagReader>(reader: &mut R) -> Result<Self> {
+        reader.read_parser(Self::parse)
+    }
+}
diff --git a/src/parse/header.rs b/src/parse/header.rs
index a9005b6..96b0eaa 100644
--- a/src/parse/header.rs
+++ b/src/parse/header.rs
@@ -19,7 +19,7 @@ mod fields;
 
 pub use self::{
     error::{FieldDataError, MissingFieldError},
-    fields::Op,
+    fields::{Op, Time},
 };
 
 #[derive(Clone, Debug)]
@@ -87,19 +87,23 @@ impl Header {
     }
 
     pub fn read_op(&self) -> Result<fields::Op> {
-        self.find_field(b"op").and_then(fields::Op::parse)
+        self.find_field(b"op").and_then(fields::Op::read)
     }
 
     pub fn read_u64(&self, field: &[u8]) -> Result<u64> {
-        self.find_field(field).and_then(fields::parse_u64)
+        self.find_field(field).and_then(fields::read_u64)
+    }
+
+    pub fn read_time(&self, field: &[u8]) -> Result<Time> {
+        self.read_u64(field).map(Time::from_packed)
     }
 
     pub fn read_u32(&self, field: &[u8]) -> Result<u32> {
-        self.find_field(field).and_then(fields::parse_u32)
+        self.find_field(field).and_then(fields::read_u32)
     }
 
     pub fn read_string(&self, field: &[u8]) -> Result<String> {
-        self.find_field(field).and_then(fields::parse_string)
+        self.find_field(field).and_then(fields::read_string)
     }
 }
 
diff --git a/src/parse/header/fields.rs b/src/parse/header/fields.rs
index 44433cf..6ed9195 100644
--- a/src/parse/header/fields.rs
+++ b/src/parse/header/fields.rs
@@ -5,6 +5,8 @@ use nom::{
 };
 use num_enum::TryFromPrimitive;
 
+use crate::parse::IResult;
+
 use super::{FieldDataError, Input, Result};
 
 #[derive(Clone, Copy, Debug, TryFromPrimitive, PartialEq)]
@@ -19,7 +21,7 @@ pub enum Op {
 }
 
 impl Op {
-    pub fn parse(input: Input) -> Result<Self> {
+    pub fn read(input: Input) -> Result<Self> {
         let (_, op) = all_consuming(le_u8)
             .parse(input)
             .map_err(FieldDataError::from)?;
@@ -27,20 +29,44 @@ impl Op {
     }
 }
 
-pub fn parse_u32(input: Input) -> Result<u32> {
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Time {
+    pub sec: u32,
+    pub nsec: u32,
+}
+
+impl Time {
+    pub fn from_packed(packed: u64) -> Time {
+        Time {
+            sec: packed as u32,
+            nsec: (packed >> 32) as u32,
+        }
+    }
+
+    pub fn parse(input: Input) -> IResult<Self> {
+        le_u64.map(Time::from_packed).parse(input)
+    }
+
+    pub fn read(input: Input) -> Result<Self> {
+        let (_, x) = Self::parse(input).map_err(FieldDataError::from)?;
+        Ok(x)
+    }
+}
+
+pub fn read_u32(input: Input) -> Result<u32> {
     let (_, x) = all_consuming(le_u32)
         .parse(input)
         .map_err(FieldDataError::from)?;
     Ok(x)
 }
 
-pub fn parse_u64(input: Input) -> Result<u64> {
+pub fn read_u64(input: Input) -> Result<u64> {
     let (_, x) = all_consuming(le_u64)
         .parse(input)
         .map_err(FieldDataError::from)?;
     Ok(x)
 }
 
-pub fn parse_string(input: Input) -> Result<String> {
+pub fn read_string(input: Input) -> Result<String> {
     Ok(String::from_utf8(input.to_owned())?)
 }