fix: mark fileStart mandatory on MP4BoxBuffer

src/DataStream.ts

@@ -36,7 +36,7 @@ export class DataStream {
 
   _buffer?: MP4BoxBuffer;
   _byteOffset?: number;
-  _dataView?: DataView<ArrayBuffer>;
+  _dataView?: DataView<MP4BoxBuffer>;
 
   endianness: boolean;
   position: number;
@@ -50,14 +50,12 @@ export class DataStream {
    * @param endianness DataStream.BIG_ENDIAN or DataStream.LITTLE_ENDIAN (the default).
    */
   constructor(
-    arrayBuffer?: ArrayBuffer | DataView<ArrayBuffer> | number,
+    arrayBuffer?: DataView<MP4BoxBuffer> | number,
     byteOffset?: number,
     endianness?: boolean | null,
   ) {
     this._byteOffset = byteOffset || 0;
-    if (arrayBuffer instanceof ArrayBuffer) {
-      this.buffer = arrayBuffer;
-    } else if (arrayBuffer instanceof DataView) {
+    if (arrayBuffer instanceof DataView) {
       this.dataView = arrayBuffer;
       if (byteOffset) this._byteOffset += byteOffset;
     } else {
@@ -181,7 +179,7 @@ export class DataStream {
   get dataView() {
     return this._dataView;
   }
-  set dataView(value: DataView<ArrayBuffer>) {
+  set dataView(value: DataView<MP4BoxBuffer>) {
     this._byteOffset = value.byteOffset;
     this._buffer = value.buffer;
     this._dataView = new DataView(this._buffer, this._byteOffset);
@@ -346,7 +344,7 @@ export class DataStream {
    * @param e Endianness of the data to read.
    * @return The read Uint8Array.
    */
-  readUint8Array(length: number | null) {
+  readUint8Array(length: number | null): Uint8Array {
     length = length === null ? this.byteLength - this.position : length;
     const arr = new Uint8Array(length);
     DataStream.memcpy(

src/boxes/esds.ts

@@ -2,6 +2,7 @@ import { FullBox } from '#/box';
 import type { MultiBufferStream } from '#/buffer';
 import { DataStream } from '#/DataStream';
 import type { ES_Descriptor } from '#/descriptor';
+import type { MP4BoxBuffer } from '#/mp4boxbuffer';
 import { DescriptorRegistry } from '#/registry';
 
 export class esdsBox extends FullBox {
@@ -16,8 +17,15 @@ export class esdsBox extends FullBox {
     // NOTE:    This used to be `typeof MPEG4DescriptorParser !== 'undefined'`
     if ('MPEG4DescriptorParser' in DescriptorRegistry) {
       const esd_parser = new DescriptorRegistry.MPEG4DescriptorParser();
+      const arrayBuffer = new ArrayBuffer(esd_data.length);
+      const uint8Array = new Uint8Array(arrayBuffer);
+      uint8Array.set(esd_data);
+
+      const mp4Buffer: MP4BoxBuffer = Object.assign(arrayBuffer, { fileStart: 0 });
+      const mp4Dataview = new DataView(mp4Buffer, 0, arrayBuffer.byteLength);
+
       this.esd = esd_parser.parseOneDescriptor(
-        new DataStream(esd_data.buffer, 0, DataStream.BIG_ENDIAN),
+        new DataStream(mp4Dataview, 0, DataStream.BIG_ENDIAN),
       ) as ES_Descriptor;
     }
   }

src/buffer.ts

@@ -8,15 +8,21 @@ import type { MP4BoxBuffer } from './mp4boxbuffer';
  * @param buffer2
  * @return the concatenation of buffer1 and buffer2 in that order
  */
-function concatBuffers(buffer1: ArrayBuffer, buffer2: ArrayBuffer) {
+function concatBuffers(buffer1: MP4BoxBuffer, buffer2: MP4BoxBuffer): MP4BoxBuffer {
   Log.debug(
     'ArrayBuffer',
     'Trying to create a new buffer of size: ' + (buffer1.byteLength + buffer2.byteLength),
   );
   const tmp = new Uint8Array(buffer1.byteLength + buffer2.byteLength);
   tmp.set(new Uint8Array(buffer1), 0);
   tmp.set(new Uint8Array(buffer2), buffer1.byteLength);
-  return tmp.buffer as MP4BoxBuffer;
+
+  const arrayBuffer = tmp.buffer;
+
+  return Object.assign(arrayBuffer, {
+    fileStart: buffer1.fileStart,
+    usedBytes: buffer1.usedBytes + buffer2.usedBytes,
+  });
 }
 
 /**
@@ -31,7 +37,7 @@ export class MultiBufferStream extends DataStream {
   bufferIndex: number;
 
   constructor(buffer?: MP4BoxBuffer) {
-    super(new ArrayBuffer(), 0, DataStream.BIG_ENDIAN);
+    super(undefined, 0, DataStream.BIG_ENDIAN);
     // List of ArrayBuffers, with a fileStart property, sorted in fileStart order and non-overlapping
     this.buffers = [];
     this.bufferIndex = -1;
@@ -73,14 +79,13 @@ export class MultiBufferStream extends DataStream {
    * @param  {ArrayBuffer} buffer
    * @param  {Number}      offset    the start of new buffer
    * @param  {Number}      newLength the length of the new buffer
-   * @return {ArrayBuffer}           the new buffer
+   * @return {MP4BoxBuffer}           the new buffer
    */
-  reduceBuffer(buffer: MP4BoxBuffer, offset: number, newLength: number) {
+  reduceBuffer(buffer: MP4BoxBuffer, offset: number, newLength: number): MP4BoxBuffer {
     const smallB = new Uint8Array(newLength);
     smallB.set(new Uint8Array(buffer, offset, newLength));
-    (smallB.buffer as MP4BoxBuffer).fileStart = buffer.fileStart + offset;
-    (smallB.buffer as MP4BoxBuffer).usedBytes = 0;
-    return smallB.buffer as MP4BoxBuffer;
+
+    return Object.assign(smallB.buffer, { fileStart: buffer.fileStart + offset, usedBytes: 0 });
   }
 
   /**

src/mp4boxbuffer.ts

@@ -1,4 +1,4 @@
 export class MP4BoxBuffer extends ArrayBuffer {
-  fileStart?: number;
+  fileStart: number;
   usedBytes?: number;
 }