MP4: Demote missing mdat atom error

CHANGELOG.md

@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+* **MP4**: A missing `mdat` atom is no longer a hard error when reading properties ([PR](https://github.com/Serial-ATA/lofty-rs/pull/515))
+ * This is now only an error in `Strict` mode. Note that any properties read in a file with no `mdat` atom are essentially useless.
+
 ## [0.22.3] - 2025-04-04
 
 ### Added

lofty/src/mp4/properties.rs

@@ -517,7 +517,18 @@ where
 if duration > 0 {
 // TODO: We should keep track of the `mdat` length when first reading the file.
 // This extra read is unnecessary.
-let mdat_len = mdat_length(reader)?;
+let mdat_len;
+match mdat_length(reader) {
+Ok(len) => mdat_len = len,
+Err(err) => {
+if parse_mode == ParsingMode::Strict {
+return Err(err);
+}
+
+log::warn!("No \"mdat\" atom found, any audio properties will be useless.");
+return Ok(properties);
+},
+}
 
 if let Some(stts) = stts {
 let stts_specifies_duration =
@@ -547,8 +558,7 @@ where
 if properties.audio_bitrate == 0 {
 log::warn!("Estimating audio bitrate from 'mdat' size");
 
-properties.audio_bitrate =
-(u128::from(mdat_length(reader)? * 8) / duration_millis) as u32;
+properties.audio_bitrate = (u128::from(mdat_len * 8) / duration_millis) as u32;
 }
 }