add creation and modification fields to MediaContext

The mvhd creation and modification times are now extracted from the moov if
present.  While these aren't needed to play the MP4, they can be useful for
applications which allow sorting and/or searching by creation or modification
time.

Author: dicej

mp4parse/src/lib.rs

@@ -266,6 +266,8 @@ struct FileTypeBox {
 /// Movie header box 'mvhd'.
 #[derive(Debug)]
 struct MovieHeaderBox {
+    creation: u64,
+    modification: u64,
     pub timescale: u32,
     duration: u64,
 }
@@ -777,9 +779,14 @@ pub enum XmlBox {
     BinaryXmlBox(TryVec<u8>),
 }
 
+#[derive(Debug)]
+pub struct UtcSecondsSince1904(pub u64);
+
 /// Internal data structures.
 #[derive(Debug, Default)]
 pub struct MediaContext {
+    pub creation: Option<UtcSecondsSince1904>,
+    pub modification: Option<UtcSecondsSince1904>,
     pub timescale: Option<MediaTimeScale>,
     /// Tracks found in the file.
     pub tracks: TryVec<Track>,
@@ -2866,16 +2873,12 @@ pub fn read_mp4<T: Read>(f: &mut T) -> Result<MediaContext> {
     context.ok_or(Error::NoMoov)
 }
 
-/// Parse a Movie Header Box
-/// See ISOBMFF (ISO 14496-12:2015) § 8.2.2
-fn parse_mvhd<T: Read>(f: &mut BMFFBox<T>) -> Result<Option<MediaTimeScale>> {
-    let mvhd = read_mvhd(f)?;
-    debug!("{:?}", mvhd);
+fn validate_timescale(mvhd: &MovieHeaderBox) -> Result<Option<MediaTimeScale>> {
     if mvhd.timescale == 0 {
-        return Err(Error::InvalidData("zero timescale in mdhd"));
+        Err(Error::InvalidData("zero timescale in mdhd"))
+    } else {
+        Ok(Some(MediaTimeScale(u64::from(mvhd.timescale))))
     }
-    let timescale = Some(MediaTimeScale(u64::from(mvhd.timescale)));
-    Ok(timescale)
 }
 
 /// Parse a Movie Box
@@ -2885,6 +2888,8 @@ fn parse_mvhd<T: Read>(f: &mut BMFFBox<T>) -> Result<Option<MediaTimeScale>> {
 /// such as with tests/test_case_1185230.mp4.
 fn read_moov<T: Read>(f: &mut BMFFBox<T>, context: Option<MediaContext>) -> Result<MediaContext> {
     let MediaContext {
+        mut creation,
+        mut modification,
         mut timescale,
         mut tracks,
         mut mvex,
@@ -2898,7 +2903,11 @@ fn read_moov<T: Read>(f: &mut BMFFBox<T>, context: Option<MediaContext>) -> Resu
     while let Some(mut b) = iter.next_box()? {
         match b.head.name {
             BoxType::MovieHeaderBox => {
-                timescale = parse_mvhd(&mut b)?;
+                let mvhd = read_mvhd(&mut b)?;
+                debug!("{:?}", mvhd);
+                creation = Some(UtcSecondsSince1904(mvhd.creation));
+                modification = Some(UtcSecondsSince1904(mvhd.modification));
+                timescale = validate_timescale(&mvhd)?;
             }
             BoxType::TrackBox => {
                 let mut track = Track::new(tracks.len());
@@ -2929,6 +2938,8 @@ fn read_moov<T: Read>(f: &mut BMFFBox<T>, context: Option<MediaContext>) -> Resu
     }
 
     Ok(MediaContext {
+        creation,
+        modification,
         timescale,
         tracks,
         mvex,
@@ -3204,33 +3215,39 @@ fn read_ftyp<T: Read>(src: &mut BMFFBox<T>) -> Result<FileTypeBox> {
 /// Parse an mvhd box.
 fn read_mvhd<T: Read>(src: &mut BMFFBox<T>) -> Result<MovieHeaderBox> {
     let (version, _) = read_fullbox_extra(src)?;
+    let to_u64 = |n| {
+        if n == std::u32::MAX {
+            std::u64::MAX
+        } else {
+            u64::from(n)
+        }
+    };
+    let creation;
+    let modification;
     match version {
         // 64 bit creation and modification times.
         1 => {
-            skip(src, 16)?;
+            creation = be_u64(src)?;
+            modification = be_u64(src)?;
         }
         // 32 bit creation and modification times.
         0 => {
-            skip(src, 8)?;
+            creation = to_u64(be_u32(src)?);
+            modification = to_u64(be_u32(src)?);
         }
         _ => return Err(Error::InvalidData("unhandled mvhd version")),
     }
     let timescale = be_u32(src)?;
     let duration = match version {
         1 => be_u64(src)?,
-        0 => {
-            let d = be_u32(src)?;
-            if d == std::u32::MAX {
-                std::u64::MAX
-            } else {
-                u64::from(d)
-            }
-        }
+        0 => to_u64(be_u32(src)?),
         _ => return Err(Error::InvalidData("unhandled mvhd version")),
     };
     // Skip remaining fields.
     skip(src, 80)?;
     Ok(MovieHeaderBox {
+        creation,
+        modification,
         timescale,
         duration,
     })

mp4parse/src/tests.rs

@@ -385,7 +385,7 @@ fn read_mvhd_invalid_timescale() {
     let mut stream = iter.next_box().unwrap().unwrap();
     assert_eq!(stream.head.name, BoxType::MovieHeaderBox);
     assert_eq!(stream.head.size, 120);
-    let r = super::parse_mvhd(&mut stream);
+    let r = super::validate_timescale(&super::read_mvhd(&mut stream).unwrap());
     assert!(r.is_err());
 }