diff --git a/src/error.rs b/src/error.rs
index 11690f0..a09b982 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -26,4 +26,6 @@ pub enum Error {
     EntryInTrunNotFound(u32, BoxType, u32),
     #[error("{0} version {1} is not supported")]
     UnsupportedBoxVersion(BoxType, u8),
+    #[error("{0}")]
+    GenericError(String),
 }
diff --git a/src/mp4box/avc1.rs b/src/mp4box/avc1.rs
index f386f9a..990bcee 100644
--- a/src/mp4box/avc1.rs
+++ b/src/mp4box/avc1.rs
@@ -67,10 +67,6 @@ impl Mp4Box for Avc1Box {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "data_reference_index={} width={} height={} frame_count={}",
@@ -206,10 +202,6 @@ impl Mp4Box for AvcCBox {
         size
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("avc_profile_indication={}", self.avc_profile_indication);
         Ok(s)
diff --git a/src/mp4box/co64.rs b/src/mp4box/co64.rs
index 978137e..4ab94ff 100644
--- a/src/mp4box/co64.rs
+++ b/src/mp4box/co64.rs
@@ -33,10 +33,6 @@ impl Mp4Box for Co64Box {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("entries_count={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/ctts.rs b/src/mp4box/ctts.rs
index 673e8c9..7bad066 100644
--- a/src/mp4box/ctts.rs
+++ b/src/mp4box/ctts.rs
@@ -39,10 +39,6 @@ impl Mp4Box for CttsBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("entries_count={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/data.rs b/src/mp4box/data.rs
index 19b5c77..79ef769 100644
--- a/src/mp4box/data.rs
+++ b/src/mp4box/data.rs
@@ -36,10 +36,6 @@ impl Mp4Box for DataBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("type={:?} len={}", self.data_type, self.data.len());
         Ok(s)
diff --git a/src/mp4box/dinf.rs b/src/mp4box/dinf.rs
index e365e4a..e4bb153 100644
--- a/src/mp4box/dinf.rs
+++ b/src/mp4box/dinf.rs
@@ -27,10 +27,6 @@ impl Mp4Box for DinfBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
@@ -68,15 +64,9 @@ impl<R: Read + Seek> ReadBox<&mut R> for DinfBox {
             current = reader.stream_position()?;
         }
 
-        if dref.is_none() {
-            return Err(Error::BoxNotFound(BoxType::DrefBox));
-        }
-
+        let dref = dref.ok_or(Error::BoxNotFound(BoxType::DrefBox))?;
         skip_bytes_to(reader, start + size)?;
-
-        Ok(DinfBox {
-            dref: dref.unwrap(),
-        })
+        Ok(DinfBox { dref })
     }
 }
 
@@ -131,10 +121,6 @@ impl Mp4Box for DrefBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
@@ -248,10 +234,6 @@ impl Mp4Box for UrlBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("location={}", self.location);
         Ok(s)
diff --git a/src/mp4box/edts.rs b/src/mp4box/edts.rs
index 9077bb1..22f43ee 100644
--- a/src/mp4box/edts.rs
+++ b/src/mp4box/edts.rs
@@ -36,10 +36,6 @@ impl Mp4Box for EdtsBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
diff --git a/src/mp4box/elst.rs b/src/mp4box/elst.rs
index 297fb63..1182e2a 100644
--- a/src/mp4box/elst.rs
+++ b/src/mp4box/elst.rs
@@ -47,10 +47,6 @@ impl Mp4Box for ElstBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("elst_entries={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/emsg.rs b/src/mp4box/emsg.rs
index f68ba3a..1028ed0 100644
--- a/src/mp4box/emsg.rs
+++ b/src/mp4box/emsg.rs
@@ -48,10 +48,6 @@ impl Mp4Box for EmsgBox {
             + self.message_data.len() as u64
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("id={} value={}", self.id, self.value);
         Ok(s)
@@ -131,13 +127,17 @@ impl<W: Write> WriteBox<&mut W> for EmsgBox {
                 write_null_terminated_str(writer, &self.scheme_id_uri)?;
                 write_null_terminated_str(writer, &self.value)?;
                 writer.write_u32::<BigEndian>(self.timescale)?;
-                writer.write_u32::<BigEndian>(self.presentation_time_delta.unwrap())?;
+                writer.write_u32::<BigEndian>(self.presentation_time_delta.ok_or(
+                    crate::error::Error::InvalidData("presentation_time_delta not found"),
+                )?)?;
                 writer.write_u32::<BigEndian>(self.event_duration)?;
                 writer.write_u32::<BigEndian>(self.id)?;
             }
             1 => {
                 writer.write_u32::<BigEndian>(self.timescale)?;
-                writer.write_u64::<BigEndian>(self.presentation_time.unwrap())?;
+                writer.write_u64::<BigEndian>(self.presentation_time.ok_or(
+                    crate::error::Error::InvalidData("presentation_time not found"),
+                )?)?;
                 writer.write_u32::<BigEndian>(self.event_duration)?;
                 writer.write_u32::<BigEndian>(self.id)?;
                 write_null_terminated_str(writer, &self.scheme_id_uri)?;
diff --git a/src/mp4box/ftyp.rs b/src/mp4box/ftyp.rs
index 789cd4e..dd35bb5 100644
--- a/src/mp4box/ftyp.rs
+++ b/src/mp4box/ftyp.rs
@@ -30,10 +30,6 @@ impl Mp4Box for FtypBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let mut compatible_brands = Vec::new();
         for brand in self.compatible_brands.iter() {
diff --git a/src/mp4box/hdlr.rs b/src/mp4box/hdlr.rs
index b9d86a9..ceb8bee 100644
--- a/src/mp4box/hdlr.rs
+++ b/src/mp4box/hdlr.rs
@@ -31,10 +31,6 @@ impl Mp4Box for HdlrBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("handler_type={} name={}", self.handler_type, self.name);
         Ok(s)
diff --git a/src/mp4box/hev1.rs b/src/mp4box/hev1.rs
index 3070fb8..e662e54 100644
--- a/src/mp4box/hev1.rs
+++ b/src/mp4box/hev1.rs
@@ -67,10 +67,6 @@ impl Mp4Box for Hev1Box {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "data_reference_index={} width={} height={} frame_count={}",
@@ -204,10 +200,6 @@ impl Mp4Box for HvcCBox {
                 .sum::<u64>()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         Ok(format!("configuration_version={} general_profile_space={} general_tier_flag={} general_profile_idc={} general_profile_compatibility_flags={} general_constraint_indicator_flag={} general_level_idc={} min_spatial_segmentation_idc={} parallelism_type={} chroma_format_idc={} bit_depth_luma_minus8={} bit_depth_chroma_minus8={} avg_frame_rate={} constant_frame_rate={} num_temporal_layers={} temporal_id_nested={} length_size_minus_one={}", 
             self.configuration_version,
diff --git a/src/mp4box/ilst.rs b/src/mp4box/ilst.rs
index d0292a3..9be0343 100644
--- a/src/mp4box/ilst.rs
+++ b/src/mp4box/ilst.rs
@@ -36,10 +36,6 @@ impl Mp4Box for IlstBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("item_count={}", self.items.len());
         Ok(s)
@@ -153,15 +149,9 @@ impl<R: Read + Seek> ReadBox<&mut R> for IlstItemBox {
             current = reader.stream_position()?;
         }
 
-        if data.is_none() {
-            return Err(Error::BoxNotFound(BoxType::DataBox));
-        }
-
+        let data = data.ok_or(Error::BoxNotFound(BoxType::DataBox))?;
         skip_bytes_to(reader, start + size)?;
-
-        Ok(IlstItemBox {
-            data: data.unwrap(),
-        })
+        Ok(IlstItemBox { data })
     }
 }
 
diff --git a/src/mp4box/mdhd.rs b/src/mp4box/mdhd.rs
index 31c65a8..bd63a87 100644
--- a/src/mp4box/mdhd.rs
+++ b/src/mp4box/mdhd.rs
@@ -57,10 +57,6 @@ impl Mp4Box for MdhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "creation_time={} timescale={} duration={} language={}",
diff --git a/src/mp4box/mdia.rs b/src/mp4box/mdia.rs
index 423bf72..1900916 100644
--- a/src/mp4box/mdia.rs
+++ b/src/mp4box/mdia.rs
@@ -30,10 +30,6 @@ impl Mp4Box for MdiaBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
@@ -79,23 +75,13 @@ impl<R: Read + Seek> ReadBox<&mut R> for MdiaBox {
             current = reader.stream_position()?;
         }
 
-        if mdhd.is_none() {
-            return Err(Error::BoxNotFound(BoxType::MdhdBox));
-        }
-        if hdlr.is_none() {
-            return Err(Error::BoxNotFound(BoxType::HdlrBox));
-        }
-        if minf.is_none() {
-            return Err(Error::BoxNotFound(BoxType::MinfBox));
-        }
+        let mdhd = mdhd.ok_or(Error::BoxNotFound(BoxType::MdhdBox))?;
+        let hdlr = hdlr.ok_or(Error::BoxNotFound(BoxType::HdlrBox))?;
+        let minf = minf.ok_or(Error::BoxNotFound(BoxType::MinfBox))?;
 
         skip_bytes_to(reader, start + size)?;
 
-        Ok(MdiaBox {
-            mdhd: mdhd.unwrap(),
-            hdlr: hdlr.unwrap(),
-            minf: minf.unwrap(),
-        })
+        Ok(MdiaBox { mdhd, hdlr, minf })
     }
 }
 
diff --git a/src/mp4box/mehd.rs b/src/mp4box/mehd.rs
index 63c0246..72db38a 100644
--- a/src/mp4box/mehd.rs
+++ b/src/mp4box/mehd.rs
@@ -37,10 +37,6 @@ impl Mp4Box for MehdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("fragment_duration={}", self.fragment_duration);
         Ok(s)
diff --git a/src/mp4box/meta.rs b/src/mp4box/meta.rs
index 56ca816..4fb51bc 100644
--- a/src/mp4box/meta.rs
+++ b/src/mp4box/meta.rs
@@ -62,10 +62,6 @@ impl Mp4Box for MetaBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = match self {
             Self::Mdir { .. } => "hdlr=ilst".to_string(),
diff --git a/src/mp4box/mfhd.rs b/src/mp4box/mfhd.rs
index 7bc2f72..f1b0f9f 100644
--- a/src/mp4box/mfhd.rs
+++ b/src/mp4box/mfhd.rs
@@ -40,10 +40,6 @@ impl Mp4Box for MfhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("sequence_number={}", self.sequence_number);
         Ok(s)
diff --git a/src/mp4box/minf.rs b/src/mp4box/minf.rs
index 5ea853b..20d22a0 100644
--- a/src/mp4box/minf.rs
+++ b/src/mp4box/minf.rs
@@ -44,10 +44,6 @@ impl Mp4Box for MinfBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
@@ -97,20 +93,16 @@ impl<R: Read + Seek> ReadBox<&mut R> for MinfBox {
             current = reader.stream_position()?;
         }
 
-        if dinf.is_none() {
-            return Err(Error::BoxNotFound(BoxType::DinfBox));
-        }
-        if stbl.is_none() {
-            return Err(Error::BoxNotFound(BoxType::StblBox));
-        }
+        let dinf = dinf.ok_or(Error::BoxNotFound(BoxType::DinfBox))?;
+        let stbl = stbl.ok_or(Error::BoxNotFound(BoxType::StblBox))?;
 
         skip_bytes_to(reader, start + size)?;
 
         Ok(MinfBox {
             vmhd,
             smhd,
-            dinf: dinf.unwrap(),
-            stbl: stbl.unwrap(),
+            dinf,
+            stbl,
         })
     }
 }
diff --git a/src/mp4box/mod.rs b/src/mp4box/mod.rs
index 4bbdd41..c4f041a 100644
--- a/src/mp4box/mod.rs
+++ b/src/mp4box/mod.rs
@@ -57,6 +57,7 @@
 //!
 
 use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
+use serde::Serialize;
 use std::convert::TryInto;
 use std::io::{Read, Seek, SeekFrom, Write};
 
@@ -244,7 +245,12 @@ boxtype! {
 pub trait Mp4Box: Sized {
     fn box_type(&self) -> BoxType;
     fn box_size(&self) -> u64;
-    fn to_json(&self) -> Result<String>;
+    fn to_json(&self) -> Result<String>
+    where
+        Self: Serialize,
+    {
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
+    }
     fn summary(&self) -> Result<String>;
 }
 
@@ -274,11 +280,15 @@ impl BoxHeader {
         reader.read_exact(&mut buf)?;
 
         // Get size.
-        let s = buf[0..4].try_into().unwrap();
+        let s = buf[0..4]
+            .try_into()
+            .map_err(|_e| crate::error::Error::InvalidData("could not get slice"))?;
         let size = u32::from_be_bytes(s);
 
         // Get box type string.
-        let t = buf[4..8].try_into().unwrap();
+        let t = buf[4..8]
+            .try_into()
+            .map_err(|_e| crate::error::Error::InvalidData("could not get slice"))?;
         let typ = u32::from_be_bytes(t);
 
         // Get largesize if size is 1
diff --git a/src/mp4box/moof.rs b/src/mp4box/moof.rs
index 20c3565..c4839a2 100644
--- a/src/mp4box/moof.rs
+++ b/src/mp4box/moof.rs
@@ -35,10 +35,6 @@ impl Mp4Box for MoofBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("trafs={}", self.trafs.len());
         Ok(s)
@@ -80,16 +76,9 @@ impl<R: Read + Seek> ReadBox<&mut R> for MoofBox {
             current = reader.stream_position()?;
         }
 
-        if mfhd.is_none() {
-            return Err(Error::BoxNotFound(BoxType::MfhdBox));
-        }
-
+        let mfhd = mfhd.ok_or(Error::BoxNotFound(BoxType::MfhdBox))?;
         skip_bytes_to(reader, start + size)?;
-
-        Ok(MoofBox {
-            mfhd: mfhd.unwrap(),
-            trafs,
-        })
+        Ok(MoofBox { mfhd, trafs })
     }
 }
 
diff --git a/src/mp4box/moov.rs b/src/mp4box/moov.rs
index ac19381..00ef2f9 100644
--- a/src/mp4box/moov.rs
+++ b/src/mp4box/moov.rs
@@ -51,10 +51,6 @@ impl Mp4Box for MoovBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("traks={}", self.traks.len());
         Ok(s)
@@ -109,14 +105,10 @@ impl<R: Read + Seek> ReadBox<&mut R> for MoovBox {
             current = reader.stream_position()?;
         }
 
-        if mvhd.is_none() {
-            return Err(Error::BoxNotFound(BoxType::MvhdBox));
-        }
-
+        let mvhd = mvhd.ok_or(Error::BoxNotFound(BoxType::MvhdBox))?;
         skip_bytes_to(reader, start + size)?;
-
         Ok(MoovBox {
-            mvhd: mvhd.unwrap(),
+            mvhd,
             meta,
             udta,
             mvex,
diff --git a/src/mp4box/mp4a.rs b/src/mp4box/mp4a.rs
index a80c6c4..db1dd5c 100644
--- a/src/mp4box/mp4a.rs
+++ b/src/mp4box/mp4a.rs
@@ -60,10 +60,6 @@ impl Mp4Box for Mp4aBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "channel_count={} sample_size={} sample_rate={}",
@@ -188,10 +184,6 @@ impl Mp4Box for EsdsBox {
             + ESDescriptor::desc_size() as u64
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         Ok(String::new())
     }
diff --git a/src/mp4box/mvex.rs b/src/mp4box/mvex.rs
index 8be683b..6e269f7 100644
--- a/src/mp4box/mvex.rs
+++ b/src/mp4box/mvex.rs
@@ -29,10 +29,6 @@ impl Mp4Box for MvexBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
diff --git a/src/mp4box/mvhd.rs b/src/mp4box/mvhd.rs
index 462a29b..9bcd0db 100644
--- a/src/mp4box/mvhd.rs
+++ b/src/mp4box/mvhd.rs
@@ -66,10 +66,6 @@ impl Mp4Box for MvhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "creation_time={} timescale={} duration={} rate={} volume={}, matrix={}, next_track_id={}",
diff --git a/src/mp4box/smhd.rs b/src/mp4box/smhd.rs
index cab7e4b..bc919e5 100644
--- a/src/mp4box/smhd.rs
+++ b/src/mp4box/smhd.rs
@@ -42,10 +42,6 @@ impl Mp4Box for SmhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("balance={}", self.balance.value());
         Ok(s)
diff --git a/src/mp4box/stbl.rs b/src/mp4box/stbl.rs
index ef8433b..03dd819 100644
--- a/src/mp4box/stbl.rs
+++ b/src/mp4box/stbl.rs
@@ -63,10 +63,6 @@ impl Mp4Box for StblBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
diff --git a/src/mp4box/stco.rs b/src/mp4box/stco.rs
index a00da8f..3ce39d9 100644
--- a/src/mp4box/stco.rs
+++ b/src/mp4box/stco.rs
@@ -33,10 +33,6 @@ impl Mp4Box for StcoBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("entries={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/stsc.rs b/src/mp4box/stsc.rs
index a2b034b..4371c39 100644
--- a/src/mp4box/stsc.rs
+++ b/src/mp4box/stsc.rs
@@ -41,10 +41,6 @@ impl Mp4Box for StscBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("entries={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/stsd.rs b/src/mp4box/stsd.rs
index af947c6..9a995bb 100644
--- a/src/mp4box/stsd.rs
+++ b/src/mp4box/stsd.rs
@@ -58,10 +58,6 @@ impl Mp4Box for StsdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
diff --git a/src/mp4box/stss.rs b/src/mp4box/stss.rs
index dd9e552..f6bed51 100644
--- a/src/mp4box/stss.rs
+++ b/src/mp4box/stss.rs
@@ -33,10 +33,6 @@ impl Mp4Box for StssBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("entries={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/stsz.rs b/src/mp4box/stsz.rs
index b07e765..738b98f 100644
--- a/src/mp4box/stsz.rs
+++ b/src/mp4box/stsz.rs
@@ -35,10 +35,6 @@ impl Mp4Box for StszBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "sample_size={} sample_count={} sample_sizes={}",
diff --git a/src/mp4box/stts.rs b/src/mp4box/stts.rs
index 82de6c5..9eab506 100644
--- a/src/mp4box/stts.rs
+++ b/src/mp4box/stts.rs
@@ -39,10 +39,6 @@ impl Mp4Box for SttsBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("entries={}", self.entries.len());
         Ok(s)
diff --git a/src/mp4box/tfdt.rs b/src/mp4box/tfdt.rs
index ef92889..aa2d5ef 100644
--- a/src/mp4box/tfdt.rs
+++ b/src/mp4box/tfdt.rs
@@ -36,10 +36,6 @@ impl Mp4Box for TfdtBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("base_media_decode_time={}", self.base_media_decode_time);
         Ok(s)
diff --git a/src/mp4box/tfhd.rs b/src/mp4box/tfhd.rs
index 5b529e6..19298a4 100644
--- a/src/mp4box/tfhd.rs
+++ b/src/mp4box/tfhd.rs
@@ -59,10 +59,6 @@ impl Mp4Box for TfhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("track_id={}", self.track_id);
         Ok(s)
diff --git a/src/mp4box/tkhd.rs b/src/mp4box/tkhd.rs
index d7bcfbe..56063b2 100644
--- a/src/mp4box/tkhd.rs
+++ b/src/mp4box/tkhd.rs
@@ -125,10 +125,6 @@ impl Mp4Box for TkhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "creation_time={} track_id={} duration={} layer={} volume={} matrix={} width={} height={}",
diff --git a/src/mp4box/traf.rs b/src/mp4box/traf.rs
index d53d713..6afc4d6 100644
--- a/src/mp4box/traf.rs
+++ b/src/mp4box/traf.rs
@@ -38,10 +38,6 @@ impl Mp4Box for TrafBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
diff --git a/src/mp4box/trak.rs b/src/mp4box/trak.rs
index e8ae760..40b06b4 100644
--- a/src/mp4box/trak.rs
+++ b/src/mp4box/trak.rs
@@ -43,10 +43,6 @@ impl Mp4Box for TrakBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = String::new();
         Ok(s)
diff --git a/src/mp4box/trex.rs b/src/mp4box/trex.rs
index 2694fd6..8cbc6e9 100644
--- a/src/mp4box/trex.rs
+++ b/src/mp4box/trex.rs
@@ -34,10 +34,6 @@ impl Mp4Box for TrexBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "track_id={} default_sample_duration={}",
diff --git a/src/mp4box/trun.rs b/src/mp4box/trun.rs
index efbb2b0..444bf9c 100644
--- a/src/mp4box/trun.rs
+++ b/src/mp4box/trun.rs
@@ -68,10 +68,6 @@ impl Mp4Box for TrunBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("sample_size={}", self.sample_count);
         Ok(s)
diff --git a/src/mp4box/tx3g.rs b/src/mp4box/tx3g.rs
index d696315..ef00900 100644
--- a/src/mp4box/tx3g.rs
+++ b/src/mp4box/tx3g.rs
@@ -61,10 +61,6 @@ impl Mp4Box for Tx3gBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!("data_reference_index={} horizontal_justification={} vertical_justification={} rgba={}{}{}{}",
             self.data_reference_index, self.horizontal_justification,
diff --git a/src/mp4box/udta.rs b/src/mp4box/udta.rs
index 9daec17..aedce92 100644
--- a/src/mp4box/udta.rs
+++ b/src/mp4box/udta.rs
@@ -34,10 +34,6 @@ impl Mp4Box for UdtaBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         Ok(String::new())
     }
diff --git a/src/mp4box/vmhd.rs b/src/mp4box/vmhd.rs
index 31f24b2..e13df77 100644
--- a/src/mp4box/vmhd.rs
+++ b/src/mp4box/vmhd.rs
@@ -38,10 +38,6 @@ impl Mp4Box for VmhdBox {
         self.get_size()
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         let s = format!(
             "graphics_mode={} op_color={}{}{}",
diff --git a/src/mp4box/vp09.rs b/src/mp4box/vp09.rs
index 0f88dd1..e3e95bc 100644
--- a/src/mp4box/vp09.rs
+++ b/src/mp4box/vp09.rs
@@ -74,10 +74,6 @@ impl Mp4Box for Vp09Box {
         0x6A
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         Ok(format!("{self:?}"))
     }
diff --git a/src/mp4box/vpcc.rs b/src/mp4box/vpcc.rs
index c9861c6..520ec29 100644
--- a/src/mp4box/vpcc.rs
+++ b/src/mp4box/vpcc.rs
@@ -31,10 +31,6 @@ impl Mp4Box for VpccBox {
         HEADER_SIZE + HEADER_EXT_SIZE + 8
     }
 
-    fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
-    }
-
     fn summary(&self) -> Result<String> {
         Ok(format!("{self:?}"))
     }
diff --git a/src/reader.rs b/src/reader.rs
index e5ac296..3c9f6c4 100644
--- a/src/reader.rs
+++ b/src/reader.rs
@@ -75,33 +75,24 @@ impl<R: Read + Seek> Mp4Reader<R> {
             current = reader.stream_position()?;
         }
 
-        if ftyp.is_none() {
-            return Err(Error::BoxNotFound(BoxType::FtypBox));
-        }
-        if moov.is_none() {
-            return Err(Error::BoxNotFound(BoxType::MoovBox));
-        }
+        let ftyp = ftyp.ok_or(Error::BoxNotFound(BoxType::FtypBox))?;
+        let moov = moov.ok_or(Error::BoxNotFound(BoxType::MoovBox))?;
 
         let size = current - start;
-        let mut tracks = if let Some(ref moov) = moov {
-            if moov.traks.iter().any(|trak| trak.tkhd.track_id == 0) {
-                return Err(Error::InvalidData("illegal track id 0"));
-            }
-            moov.traks
-                .iter()
-                .map(|trak| (trak.tkhd.track_id, Mp4Track::from(trak)))
-                .collect()
-        } else {
-            HashMap::new()
-        };
+        if moov.traks.iter().any(|trak| trak.tkhd.track_id == 0) {
+            return Err(Error::InvalidData("illegal track id 0"));
+        }
+        let mut tracks: HashMap<u32, Mp4Track> = moov
+            .traks
+            .iter()
+            .map(|trak| (trak.tkhd.track_id, Mp4Track::from(trak)))
+            .collect();
 
         // Update tracks if any fragmented (moof) boxes are found.
         if !moofs.is_empty() {
             let mut default_sample_duration = 0;
-            if let Some(ref moov) = moov {
-                if let Some(ref mvex) = &moov.mvex {
-                    default_sample_duration = mvex.trex.default_sample_duration
-                }
+            if let Some(ref mvex) = &moov.mvex {
+                default_sample_duration = mvex.trex.default_sample_duration
             }
 
             for (moof, moof_offset) in moofs.iter().zip(moof_offsets) {
@@ -120,8 +111,8 @@ impl<R: Read + Seek> Mp4Reader<R> {
 
         Ok(Mp4Reader {
             reader,
-            ftyp: ftyp.unwrap(),
-            moov: moov.unwrap(),
+            ftyp,
+            moov,
             moofs,
             emsgs,
             size,
diff --git a/src/track.rs b/src/track.rs
index 7eada83..9221f76 100644
--- a/src/track.rs
+++ b/src/track.rs
@@ -346,7 +346,10 @@ impl Mp4Track {
     }
 
     fn ctts_index(&self, sample_id: u32) -> Result<(usize, u32)> {
-        let ctts = self.trak.mdia.minf.stbl.ctts.as_ref().unwrap();
+        let ctts = self.trak.mdia.minf.stbl.ctts.as_ref().ok_or(
+            // todo: is this the correct error to return here?
+            crate::error::Error::BoxNotFound(BoxType::CttsBox),
+        )?;
         let mut sample_count: u32 = 1;
         for (i, entry) in ctts.entries.iter().enumerate() {
             let next_sample_count =
@@ -369,30 +372,36 @@ impl Mp4Track {
     }
 
     /// return `(traf_idx, sample_idx_in_trun)`
-    fn find_traf_idx_and_sample_idx(&self, sample_id: u32) -> Option<(usize, usize)> {
+    fn find_traf_idx_and_sample_idx(&self, sample_id: u32) -> Result<Option<(usize, usize)>> {
         let global_idx = sample_id - 1;
         let mut offset = 0;
         for traf_idx in 0..self.trafs.len() {
             if let Some(trun) = &self.trafs[traf_idx].trun {
                 let sample_count = trun.sample_count;
                 if sample_count > (global_idx - offset) {
-                    return Some((traf_idx, (global_idx - offset) as _));
+                    return Ok(Some((traf_idx, (global_idx - offset) as _)));
                 }
-                offset = offset
-                    .checked_add(sample_count)
-                    .expect("attempt to sum trun sample_count with overflow");
+                offset =
+                    offset
+                        .checked_add(sample_count)
+                        .ok_or(crate::error::Error::InvalidData(
+                            "attempt to sum trun sample_count with overflow",
+                        ))?;
             }
         }
-        None
+        Ok(None)
     }
 
     fn sample_size(&self, sample_id: u32) -> Result<u32> {
         if !self.trafs.is_empty() {
-            if let Some((traf_idx, sample_idx)) = self.find_traf_idx_and_sample_idx(sample_id) {
+            if let Some((traf_idx, sample_idx)) = self.find_traf_idx_and_sample_idx(sample_id)? {
                 if let Some(size) = self.trafs[traf_idx]
                     .trun
                     .as_ref()
-                    .unwrap()
+                    .ok_or(crate::error::Error::BoxInTrafNotFound(
+                        traf_idx as u32,
+                        BoxType::TrunBox,
+                    ))?
                     .sample_sizes
                     .get(sample_idx)
                 {
@@ -439,7 +448,7 @@ impl Mp4Track {
 
     pub fn sample_offset(&self, sample_id: u32) -> Result<u64> {
         if !self.trafs.is_empty() {
-            if let Some((traf_idx, sample_idx)) = self.find_traf_idx_and_sample_idx(sample_id) {
+            if let Ok(Some((traf_idx, sample_idx))) = self.find_traf_idx_and_sample_idx(sample_id) {
                 let mut sample_offset = self.trafs[traf_idx]
                     .tfhd
                     .base_data_offset
@@ -472,7 +481,13 @@ impl Mp4Track {
             let stsc_index = self.stsc_index(sample_id)?;
 
             let stsc = &self.trak.mdia.minf.stbl.stsc;
-            let stsc_entry = stsc.entries.get(stsc_index).unwrap();
+            let stsc_entry =
+                stsc.entries
+                    .get(stsc_index)
+                    .ok_or(crate::error::Error::GenericError(format!(
+                        "stsc entry not found for sample_id: {}, stsc_idx: {}",
+                        sample_id, stsc_index
+                    )))?;
 
             let first_chunk = stsc_entry.first_chunk;
             let first_sample = stsc_entry.first_sample;
@@ -503,7 +518,7 @@ impl Mp4Track {
         if !self.trafs.is_empty() {
             let mut base_start_time = 0;
             let mut default_sample_duration = self.default_sample_duration;
-            if let Some((traf_idx, sample_idx)) = self.find_traf_idx_and_sample_idx(sample_id) {
+            if let Ok(Some((traf_idx, sample_idx))) = self.find_traf_idx_and_sample_idx(sample_id) {
                 let traf = &self.trafs[traf_idx];
                 if let Some(tfdt) = &traf.tfdt {
                     base_start_time = tfdt.base_media_decode_time;
@@ -557,24 +572,29 @@ impl Mp4Track {
         }
     }
 
-    fn sample_rendering_offset(&self, sample_id: u32) -> i32 {
+    fn sample_rendering_offset(&self, sample_id: u32) -> Result<i32> {
         if !self.trafs.is_empty() {
-            if let Some((traf_idx, sample_idx)) = self.find_traf_idx_and_sample_idx(sample_id) {
+            if let Ok(Some((traf_idx, sample_idx))) = self.find_traf_idx_and_sample_idx(sample_id) {
                 if let Some(cts) = self.trafs[traf_idx]
                     .trun
                     .as_ref()
                     .and_then(|trun| trun.sample_cts.get(sample_idx))
                 {
-                    return *cts as i32;
+                    return Ok(*cts as i32);
                 }
             }
         } else if let Some(ref ctts) = self.trak.mdia.minf.stbl.ctts {
             if let Ok((ctts_index, _)) = self.ctts_index(sample_id) {
-                let ctts_entry = ctts.entries.get(ctts_index).unwrap();
-                return ctts_entry.sample_offset;
+                let ctts_entry =
+                    ctts.entries
+                        .get(ctts_index)
+                        .ok_or(crate::error::Error::InvalidData(
+                            "ctts not found after ctts_index was returned",
+                        ))?;
+                return Ok(ctts_entry.sample_offset);
             }
         }
-        0
+        Ok(0)
     }
 
     fn is_sync_sample(&self, sample_id: u32) -> bool {
@@ -610,8 +630,8 @@ impl Mp4Track {
         reader.seek(SeekFrom::Start(sample_offset))?;
         reader.read_exact(&mut buffer)?;
 
-        let (start_time, duration) = self.sample_time(sample_id).unwrap(); // XXX
-        let rendering_offset = self.sample_rendering_offset(sample_id);
+        let (start_time, duration) = self.sample_time(sample_id)?; // XXX
+        let rendering_offset = self.sample_rendering_offset(sample_id)?;
         let is_sync = self.is_sync_sample(sample_id);
 
         Ok(Some(Mp4Sample {
@@ -840,9 +860,16 @@ impl Mp4TrackWriter {
         Ok(self.trak.tkhd.duration)
     }
 
-    fn chunk_count(&self) -> u32 {
-        let co64 = self.trak.mdia.minf.stbl.co64.as_ref().unwrap();
-        co64.entries.len() as u32
+    fn chunk_count(&self) -> Result<u32> {
+        let co64 = self
+            .trak
+            .mdia
+            .minf
+            .stbl
+            .co64
+            .as_ref()
+            .ok_or(crate::error::Error::BoxNotFound(BoxType::Co64Box))?;
+        Ok(co64.entries.len() as u32)
     }
 
     fn update_sample_to_chunk(&mut self, chunk_id: u32) {
@@ -861,9 +888,17 @@ impl Mp4TrackWriter {
         self.trak.mdia.minf.stbl.stsc.entries.push(entry);
     }
 
-    fn update_chunk_offsets(&mut self, offset: u64) {
-        let co64 = self.trak.mdia.minf.stbl.co64.as_mut().unwrap();
+    fn update_chunk_offsets(&mut self, offset: u64) -> Result<()> {
+        let co64 = self
+            .trak
+            .mdia
+            .minf
+            .stbl
+            .co64
+            .as_mut()
+            .ok_or(crate::error::Error::BoxNotFound(BoxType::Co64Box))?;
         co64.entries.push(offset);
+        Ok(())
     }
 
     fn write_chunk<W: Write + Seek>(&mut self, writer: &mut W) -> Result<()> {
@@ -874,8 +909,8 @@ impl Mp4TrackWriter {
 
         writer.write_all(&self.chunk_buffer)?;
 
-        self.update_sample_to_chunk(self.chunk_count() + 1);
-        self.update_chunk_offsets(chunk_offset);
+        self.update_sample_to_chunk(self.chunk_count()? + 1);
+        self.update_chunk_offsets(chunk_offset)?;
 
         self.chunk_buffer.clear();
         self.chunk_samples = 0;
@@ -908,7 +943,15 @@ impl Mp4TrackWriter {
             // mp4a.esds.es_desc.dec_config.max_bitrate
             // mp4a.esds.es_desc.dec_config.avg_bitrate
         }
-        if let Ok(stco) = StcoBox::try_from(self.trak.mdia.minf.stbl.co64.as_ref().unwrap()) {
+        if let Ok(stco) = StcoBox::try_from(
+            self.trak
+                .mdia
+                .minf
+                .stbl
+                .co64
+                .as_ref()
+                .ok_or(crate::error::Error::BoxNotFound(BoxType::Co64Box))?,
+        ) {
             self.trak.mdia.minf.stbl.stco = Some(stco);
             self.trak.mdia.minf.stbl.co64 = None;
         }