fix: correctly detect fragmented files

- Display total fragment duration on the demo

closes #504

Author: DenizUgur

README.md

@@ -156,7 +156,7 @@ The `info` argument is an object with the following structure.
 - **duration**: Number, providing the duration of the movie (unfragmented part) in timescale units,
 - **isProgressive**: boolean, indicating if the file can be played progressively,
 - **isFragmented**: boolean, indicating if the file is already fragmented,
-- **fragment_duration**: Number, giving the duration of the fragmented part of the file, in timescale units,
+- **fragment_duration**: Fraction, giving the duration of the fragmented part of the file along with the timescale (in the form `{ num: Number, den: Number }`)
 - **hasIOD**: boolean, indicating if the file contains an MPEG-4 Initial Object Descriptor
 - **tracks**: Array of track information objects
 

demo/index.js

@@ -551,7 +551,7 @@ function load() {
     Log.info('Application', 'Movie information received');
     movieInfo = info;
     if (info.isFragmented) {
-      ms.duration = info.fragment_duration / info.timescale;
+      ms.duration = info.fragment_duration.num / info.fragment_duration.den;
     } else {
       ms.duration = info.duration / info.timescale;
     }

demo/movieInfoDisplay.js

@@ -294,9 +294,9 @@ function displayMovieInfo(info, div, _displaySourceBuffer) {
   if (info.isFragmented) {
     html +=
       '<tr><th>Fragmented duration</th><td>' +
-      info.fragment_duration +
+      info.fragment_duration.num +
       (info.fragment_duration
-        ? ' - ' + Log.getDurationString(info.fragment_duration, info.timescale)
+        ? ' - ' + Log.getDurationString(info.fragment_duration.num, info.fragment_duration.den)
         : '') +
       '</td></tr>';
   }

entries/types.ts

@@ -196,7 +196,7 @@ export interface Movie {
   brands: Array<string>;
   created: Date;
   duration: number;
-  fragment_duration?: number;
+  fragment_duration?: { num: number; den: number };
   hasIOD: boolean;
   hintTracks: Array<Track>;
   isFragmented: boolean;

src/isofile.ts

@@ -577,6 +577,36 @@ export class ISOFile<TSegmentUser = unknown, TSampleUser = unknown> {
     return nextFileStart;
   }
 
+  getFragmentDuration() {
+    const mvex = this.getBox('mvex');
+    if (!mvex) return;
+
+    // Use mehd if available
+    if (mvex.mehd) {
+      return {
+        num: mvex.mehd.fragment_duration,
+        den: this.moov.mvhd.timescale,
+      };
+    }
+
+    // Find the longest track
+    const traks = this.getBoxes('trak', false);
+    let maximum = { num: 0, den: 1 };
+
+    for (const trak of traks) {
+      const duration = trak.samples_duration;
+      const timescale = trak.mdia.mdhd.timescale;
+      if (duration && timescale) {
+        const ratio = duration / timescale;
+        if (ratio > maximum.num / maximum.den) {
+          maximum = { num: duration, den: timescale };
+        }
+      }
+    }
+
+    return maximum;
+  }
+
   getInfo(): Movie {
     if (!this.moov) {
       return {
@@ -586,14 +616,14 @@ export class ISOFile<TSegmentUser = unknown, TSampleUser = unknown> {
     }
 
     const _1904 = new Date('1904-01-01T00:00:00Z').getTime();
-    const isFragmented = this.moov.mvex?.mehd !== undefined;
+    const isFragmented = this.getBox('mvex') !== undefined;
 
     const movie: Movie = {
       hasMoov: true,
       duration: this.moov.mvhd.duration,
       timescale: this.moov.mvhd.timescale,
       isFragmented,
-      fragment_duration: isFragmented ? this.moov.mvex.mehd.fragment_duration : undefined,
+      fragment_duration: this.getFragmentDuration(),
       isProgressive: this.isProgressive,
       hasIOD: this.moov.iods !== undefined,
       brands: [this.ftyp.major_brand].concat(this.ftyp.compatible_brands),