diff --git a/src/mp4box/avc1.rs b/src/mp4box/avc1.rs
index 7174122..7226d5d 100644
--- a/src/mp4box/avc1.rs
+++ b/src/mp4box/avc1.rs
@@ -68,7 +68,7 @@ impl Mp4Box for Avc1Box {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
@@ -200,7 +200,7 @@ impl Mp4Box for AvcCBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/co64.rs b/src/mp4box/co64.rs
index 978137e..c6f77d3 100644
--- a/src/mp4box/co64.rs
+++ b/src/mp4box/co64.rs
@@ -34,7 +34,7 @@ impl Mp4Box for Co64Box {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/ctts.rs b/src/mp4box/ctts.rs
index 673e8c9..7316c9b 100644
--- a/src/mp4box/ctts.rs
+++ b/src/mp4box/ctts.rs
@@ -40,7 +40,7 @@ impl Mp4Box for CttsBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/data.rs b/src/mp4box/data.rs
index 19b5c77..f49631e 100644
--- a/src/mp4box/data.rs
+++ b/src/mp4box/data.rs
@@ -37,7 +37,7 @@ impl Mp4Box for DataBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/dinf.rs b/src/mp4box/dinf.rs
index 46698c9..ad78a0f 100644
--- a/src/mp4box/dinf.rs
+++ b/src/mp4box/dinf.rs
@@ -28,7 +28,7 @@ impl Mp4Box for DinfBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
@@ -132,7 +132,7 @@ impl Mp4Box for DrefBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
@@ -249,7 +249,7 @@ impl Mp4Box for UrlBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/edts.rs b/src/mp4box/edts.rs
index 9077bb1..5ab5962 100644
--- a/src/mp4box/edts.rs
+++ b/src/mp4box/edts.rs
@@ -37,7 +37,7 @@ impl Mp4Box for EdtsBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/elst.rs b/src/mp4box/elst.rs
index 297fb63..79267e5 100644
--- a/src/mp4box/elst.rs
+++ b/src/mp4box/elst.rs
@@ -48,7 +48,7 @@ impl Mp4Box for ElstBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/emsg.rs b/src/mp4box/emsg.rs
index f68ba3a..c03bcae 100644
--- a/src/mp4box/emsg.rs
+++ b/src/mp4box/emsg.rs
@@ -49,7 +49,7 @@ impl Mp4Box for EmsgBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/ftyp.rs b/src/mp4box/ftyp.rs
index 789cd4e..36c8e36 100644
--- a/src/mp4box/ftyp.rs
+++ b/src/mp4box/ftyp.rs
@@ -31,7 +31,7 @@ impl Mp4Box for FtypBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/hdlr.rs b/src/mp4box/hdlr.rs
index 1ff559e..99455ce 100644
--- a/src/mp4box/hdlr.rs
+++ b/src/mp4box/hdlr.rs
@@ -32,7 +32,7 @@ impl Mp4Box for HdlrBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/hev1.rs b/src/mp4box/hev1.rs
index 3a8cfea..c0731c6 100644
--- a/src/mp4box/hev1.rs
+++ b/src/mp4box/hev1.rs
@@ -68,7 +68,7 @@ impl Mp4Box for Hev1Box {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
@@ -181,7 +181,7 @@ impl Mp4Box for HvcCBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/ilst.rs b/src/mp4box/ilst.rs
index d0292a3..5de336a 100644
--- a/src/mp4box/ilst.rs
+++ b/src/mp4box/ilst.rs
@@ -37,7 +37,7 @@ impl Mp4Box for IlstBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mdhd.rs b/src/mp4box/mdhd.rs
index 31c65a8..ee4e753 100644
--- a/src/mp4box/mdhd.rs
+++ b/src/mp4box/mdhd.rs
@@ -58,7 +58,7 @@ impl Mp4Box for MdhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mdia.rs b/src/mp4box/mdia.rs
index 423bf72..3d1e159 100644
--- a/src/mp4box/mdia.rs
+++ b/src/mp4box/mdia.rs
@@ -31,7 +31,7 @@ impl Mp4Box for MdiaBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mehd.rs b/src/mp4box/mehd.rs
index 63c0246..0bab2a5 100644
--- a/src/mp4box/mehd.rs
+++ b/src/mp4box/mehd.rs
@@ -38,7 +38,7 @@ impl Mp4Box for MehdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/meta.rs b/src/mp4box/meta.rs
index df57c77..a3fe74d 100644
--- a/src/mp4box/meta.rs
+++ b/src/mp4box/meta.rs
@@ -57,7 +57,7 @@ impl Mp4Box for MetaBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mfhd.rs b/src/mp4box/mfhd.rs
index 7bc2f72..067aa22 100644
--- a/src/mp4box/mfhd.rs
+++ b/src/mp4box/mfhd.rs
@@ -41,7 +41,7 @@ impl Mp4Box for MfhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/minf.rs b/src/mp4box/minf.rs
index 5ea853b..2ec8878 100644
--- a/src/mp4box/minf.rs
+++ b/src/mp4box/minf.rs
@@ -45,7 +45,7 @@ impl Mp4Box for MinfBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/moof.rs b/src/mp4box/moof.rs
index 20c3565..89bcf51 100644
--- a/src/mp4box/moof.rs
+++ b/src/mp4box/moof.rs
@@ -36,7 +36,7 @@ impl Mp4Box for MoofBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/moov.rs b/src/mp4box/moov.rs
index ac19381..194c9ae 100644
--- a/src/mp4box/moov.rs
+++ b/src/mp4box/moov.rs
@@ -52,7 +52,7 @@ impl Mp4Box for MoovBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mp4a.rs b/src/mp4box/mp4a.rs
index e4d6a45..e6c2a63 100644
--- a/src/mp4box/mp4a.rs
+++ b/src/mp4box/mp4a.rs
@@ -61,7 +61,7 @@ impl Mp4Box for Mp4aBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
@@ -170,7 +170,7 @@ impl Mp4Box for EsdsBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mvex.rs b/src/mp4box/mvex.rs
index 8be683b..31a9eab 100644
--- a/src/mp4box/mvex.rs
+++ b/src/mp4box/mvex.rs
@@ -30,7 +30,7 @@ impl Mp4Box for MvexBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/mvhd.rs b/src/mp4box/mvhd.rs
index 462a29b..d0593b1 100644
--- a/src/mp4box/mvhd.rs
+++ b/src/mp4box/mvhd.rs
@@ -67,7 +67,7 @@ impl Mp4Box for MvhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/smhd.rs b/src/mp4box/smhd.rs
index cab7e4b..f0a34c2 100644
--- a/src/mp4box/smhd.rs
+++ b/src/mp4box/smhd.rs
@@ -43,7 +43,7 @@ impl Mp4Box for SmhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stbl.rs b/src/mp4box/stbl.rs
index ef8433b..46199c1 100644
--- a/src/mp4box/stbl.rs
+++ b/src/mp4box/stbl.rs
@@ -64,7 +64,7 @@ impl Mp4Box for StblBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stco.rs b/src/mp4box/stco.rs
index a00da8f..daa37e0 100644
--- a/src/mp4box/stco.rs
+++ b/src/mp4box/stco.rs
@@ -34,7 +34,7 @@ impl Mp4Box for StcoBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stsc.rs b/src/mp4box/stsc.rs
index e5b444e..25d75bc 100644
--- a/src/mp4box/stsc.rs
+++ b/src/mp4box/stsc.rs
@@ -42,7 +42,7 @@ impl Mp4Box for StscBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stsd.rs b/src/mp4box/stsd.rs
index af947c6..635ac89 100644
--- a/src/mp4box/stsd.rs
+++ b/src/mp4box/stsd.rs
@@ -59,7 +59,7 @@ impl Mp4Box for StsdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stss.rs b/src/mp4box/stss.rs
index dd9e552..11b8d33 100644
--- a/src/mp4box/stss.rs
+++ b/src/mp4box/stss.rs
@@ -34,7 +34,7 @@ impl Mp4Box for StssBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stsz.rs b/src/mp4box/stsz.rs
index b07e765..38855df 100644
--- a/src/mp4box/stsz.rs
+++ b/src/mp4box/stsz.rs
@@ -36,7 +36,7 @@ impl Mp4Box for StszBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/stts.rs b/src/mp4box/stts.rs
index 82de6c5..66e76e5 100644
--- a/src/mp4box/stts.rs
+++ b/src/mp4box/stts.rs
@@ -40,7 +40,7 @@ impl Mp4Box for SttsBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/tfdt.rs b/src/mp4box/tfdt.rs
index ef92889..68e55e9 100644
--- a/src/mp4box/tfdt.rs
+++ b/src/mp4box/tfdt.rs
@@ -37,7 +37,7 @@ impl Mp4Box for TfdtBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/tfhd.rs b/src/mp4box/tfhd.rs
index e67e5cb..bc51684 100644
--- a/src/mp4box/tfhd.rs
+++ b/src/mp4box/tfhd.rs
@@ -58,7 +58,7 @@ impl Mp4Box for TfhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/tkhd.rs b/src/mp4box/tkhd.rs
index d7bcfbe..58b0f6a 100644
--- a/src/mp4box/tkhd.rs
+++ b/src/mp4box/tkhd.rs
@@ -126,7 +126,7 @@ impl Mp4Box for TkhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/traf.rs b/src/mp4box/traf.rs
index 51f812d..bdd5ffe 100644
--- a/src/mp4box/traf.rs
+++ b/src/mp4box/traf.rs
@@ -36,7 +36,7 @@ impl Mp4Box for TrafBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/trak.rs b/src/mp4box/trak.rs
index e8ae760..e0c286a 100644
--- a/src/mp4box/trak.rs
+++ b/src/mp4box/trak.rs
@@ -44,7 +44,7 @@ impl Mp4Box for TrakBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/trex.rs b/src/mp4box/trex.rs
index 2694fd6..2a45861 100644
--- a/src/mp4box/trex.rs
+++ b/src/mp4box/trex.rs
@@ -35,7 +35,7 @@ impl Mp4Box for TrexBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/trun.rs b/src/mp4box/trun.rs
index efbb2b0..793d53d 100644
--- a/src/mp4box/trun.rs
+++ b/src/mp4box/trun.rs
@@ -69,7 +69,7 @@ impl Mp4Box for TrunBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/tx3g.rs b/src/mp4box/tx3g.rs
index d696315..7edcc34 100644
--- a/src/mp4box/tx3g.rs
+++ b/src/mp4box/tx3g.rs
@@ -62,7 +62,7 @@ impl Mp4Box for Tx3gBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/udta.rs b/src/mp4box/udta.rs
index 9daec17..3fb40b4 100644
--- a/src/mp4box/udta.rs
+++ b/src/mp4box/udta.rs
@@ -35,7 +35,7 @@ impl Mp4Box for UdtaBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/vmhd.rs b/src/mp4box/vmhd.rs
index 31f24b2..3eb8c9f 100644
--- a/src/mp4box/vmhd.rs
+++ b/src/mp4box/vmhd.rs
@@ -39,7 +39,7 @@ impl Mp4Box for VmhdBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/vp09.rs b/src/mp4box/vp09.rs
index 0f88dd1..099339f 100644
--- a/src/mp4box/vp09.rs
+++ b/src/mp4box/vp09.rs
@@ -75,7 +75,7 @@ impl Mp4Box for Vp09Box {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {
diff --git a/src/mp4box/vpcc.rs b/src/mp4box/vpcc.rs
index c9861c6..f3beaf2 100644
--- a/src/mp4box/vpcc.rs
+++ b/src/mp4box/vpcc.rs
@@ -32,7 +32,7 @@ impl Mp4Box for VpccBox {
     }
 
     fn to_json(&self) -> Result<String> {
-        Ok(serde_json::to_string(&self).unwrap())
+        serde_json::to_string(&self).map_err(|e| crate::error::Error::IoError(e.into()))
     }
 
     fn summary(&self) -> Result<String> {