isomp4: fix zero track duration for fragmented mp4

symphonia-format-isomp4/src/atoms/trak.rs

@@ -20,6 +20,8 @@ pub struct TrakAtom {
     pub edts: Option<EdtsAtom>,
     /// Media atom.
     pub mdia: MdiaAtom,
+    /// Duration, equal to mdia.mdhd.duration unless it is zero, in which case it is equal to tkhd.duration.
+    pub duration: u64,
 }
 
 impl Atom for TrakAtom {
@@ -45,14 +47,19 @@ impl Atom for TrakAtom {
             }
         }
 
-        if tkhd.is_none() {
+        let Some(tkhd_atom) = tkhd
+        else {
             return decode_error("isomp4: missing tkhd atom");
-        }
+        };
 
-        if mdia.is_none() {
+        let Some(mdia_atom) = mdia
+        else {
             return decode_error("isomp4: missing mdia atom");
-        }
+        };
+
+        let duration =
+            if mdia_atom.mdhd.duration != 0 { mdia_atom.mdhd.duration } else { tkhd_atom.duration };
 
-        Ok(TrakAtom { tkhd: tkhd.unwrap(), edts, mdia: mdia.unwrap() })
+        Ok(TrakAtom { tkhd: tkhd_atom, edts, mdia: mdia_atom, duration })
     }
 }

symphonia-format-isomp4/src/demuxer.rs

@@ -56,7 +56,7 @@ impl TrackState {
 
         track
             .with_time_base(TimeBase::new(1, trak.mdia.mdhd.timescale))
-            .with_num_frames(trak.mdia.mdhd.duration);
+            .with_num_frames(trak.duration);
 
         track
     }
@@ -523,8 +523,9 @@ impl FormatReader for IsoMp4Reader<'_> {
             }
             else {
                 // No more segments. If the stream is unseekable, it may be the case that there are
-                // more segments coming. Iterate atoms until a new segment is found or the
-                // end-of-stream is reached.
+                // more segments coming. If the stream is seekable it might be fragmented and no segments are found in
+                // the moov atom. Iterate atoms until a new segment is found or the
+                // end-of-stream is reached
                 if !self.try_read_more_segments()? {
                     return Ok(None);
                 }

symphonia-format-isomp4/src/stream.rs

@@ -146,7 +146,7 @@ impl StreamSegment for MoofSegment {
             }
 
             // If a track does NOT end in this segment, then this cannot be the last segment.
-            if seq.first_ts + seq.total_sample_duration < trak.mdia.mdhd.duration {
+            if seq.first_ts + seq.total_sample_duration < trak.duration {
                 return false;
             }
         }
@@ -349,7 +349,7 @@ impl StreamSegment for MoovSegment {
     fn all_tracks_ended(&self) -> bool {
         // If a track does not end in this segment, then this cannot be the last segment.
         for trak in &self.moov.traks {
-            if trak.mdia.minf.stbl.stts.total_duration < trak.mdia.mdhd.duration {
+            if trak.mdia.minf.stbl.stts.total_duration < trak.duration {
                 return false;
             }
         }