fix: Build ESDS box missing data property

[hughfenghen]

closes #341

[DenizUgur]

Any particular reason you need the raw data and not the parsed descriptor?

[hughfenghen]

Any particular reason you need the raw data and not the parsed descriptor?

Missing the 'data' field will result in an incorrect box size, causing file parsing errors.

Some video players will lose audio when playing MP4 files that lack an esds box.

[DenizUgur]

The link you've sent is for writing the boxes. Parsing of the boxes "should" skip the box if parsing of that box was not completed successfully.

mp4box.js/src/box-parse.js

Lines 110 to 118 in 685f491

	box.parse(stream);
	diff = stream.getPosition() - (box.start+box.size);
	if (diff < 0) {
	Log.warn("BoxParser", "Parsing of box '"+box_type+"' did not read the entire indicated box data size (missing "+(-diff)+" bytes), seeking forward");
	stream.seek(box.start+box.size);
	} else if (diff > 0) {
	Log.error("BoxParser", "Parsing of box '"+box_type+"' read "+diff+" more bytes than the indicated box data size, seeking backwards");
	if (box.size !== 0) stream.seek(box.start+box.size);
	}

If you have a sample file, I could check what's wrong.

[hughfenghen]

If the ESDS box is missing the data field, refer to the following code:

this.size = (this.data ? this.data.length : 0);
this.writeHeader(stream);
if (this.data) {
  stream.writeUint8Array(this.data);
}

The box size value will be set to 0, and the raw data will not be written to the output MP4 file. This means the output MP4 file will lack the ESDS box, causing some video players (such as Windows Media Player) to lose audio when playing the file.

Sry, my previous response was ambiguous, mp4box.js does not report an error when parsing MP4 files that lack an ESDS box.

By 'parsing error,' I mean that certain players encounter issues, such as failing to output sound properly, when playing MP4 files generated by mp4box.js that lack an ESDS box.

[DenizUgur]

Okay I understand you now. The reason I'm hesitant to merge this is that, this is probably not limited to esds and the fix should be more general. I have to check it more thoroughly.

[DenizUgur]

I believe the decision not to include the data for esds and other boxes was to avoid holding references to them in memory. When parsing boxes, you rarely need the raw data.

The correct approach is to write a box writer for esds. I've already refactored the code a bit; all that remains is to complete src/writing/esds.js.