Unreasonable memory consumption during muxing stage

[recw]

Describe the bug
The Firefox extension hogs more that 12 GB of RAM while muxing a downloaded video stream of 3.5 GB. This is more than my old system with just 8 GB RAM + swap file can handle and leads to a reboot. All the while the extension displays no warning or error.

I know my MacBook is out of support. Nonetheless, I can use native muxing apps like ffmpeg or MKVToolNix without any memory issues.

To Reproduce
Steps to reproduce the behavior:

1. Go to a website streaming a big video (3.5 GB or larger)
2. Download the stream
3. Wait until all data is downloaded and muxing stage starts
4. Observe RAM consumption

Expected behavior
The extension shouldn't use up that much RAM (more than three times the stream size).

Screenshots

Desktop (please complete the following information):

• OS: Mac OSX 10.13.6 High Sierra
• Browser Firefox 115 ESR (64 bit)
• Version 5.4.4

Additional context
I also tried to download the same stream via Chromium 127 (64 bit) with the MV2 extension 5.4.4.
Here, after the downloading stage finished, I got the following error message:

Would it be possible to mux the downloaded stream chunk-wise and combine it afterwards? That should significantly reduce overall memory allocation.

[puemos]

Taking a look