fix: Fix Mp4Generator (#5566)

Fixes the mvex generation
Removes width and height from tkhd box for audio tracks

lib/util/mp4_generator.js

@@ -55,7 +55,7 @@ shaka.util.Mp4Generator = class {
     return Mp4Generator.box('moov',
         this.mvhd_(firstStreamInfo),
         traks,
-        this.mvex_(firstStreamInfo),
+        this.mvex_(),
         this.pssh_(firstStreamInfo));
   }
 
@@ -130,9 +130,14 @@ shaka.util.Mp4Generator = class {
    */
   tkhd_(streamInfo) {
     const Mp4Generator = shaka.util.Mp4Generator;
+    const ContentType = shaka.util.ManifestParserUtils.ContentType;
     const id = streamInfo.id + 1;
-    const width = streamInfo.stream.width || 0;
-    const height = streamInfo.stream.height || 0;
+    let width = streamInfo.stream.width || 0;
+    let height = streamInfo.stream.height || 0;
+    if (streamInfo.type == ContentType.AUDIO) {
+      width = 0;
+      height = 0;
+    }
     const duration = streamInfo.duration * streamInfo.timescale;
     const upperWordDuration =
         Math.floor(duration / (Mp4Generator.UINT32_MAX_ + 1));
@@ -689,13 +694,16 @@ shaka.util.Mp4Generator = class {
   /**
    * Generate a MVEX box
    *
-   * @param {shaka.util.Mp4Generator.StreamInfo} streamInfo
    * @return {!Uint8Array}
    * @private
    */
-  mvex_(streamInfo) {
+  mvex_() {
     const Mp4Generator = shaka.util.Mp4Generator;
-    return Mp4Generator.box('mvex', this.trex_(streamInfo));
+    let trexs = new Uint8Array([]);
+    for (const streamInfo of this.streamInfos_) {
+      trexs = shaka.util.Uint8ArrayUtils.concat(trexs, this.trex_(streamInfo));
+    }
+    return Mp4Generator.box('mvex', trexs);
   }
 
   /**