Save client side large set of data to local file on Chrome Android with streams

Question

I have a code that decompiles a video and generates a new video, all on client side. As the videos are large, the output of the video muxer is directed to a writablestream, so the data is consumed as it is generated to prevent excessive memory usage. On chrome for windows, I get the writable stream with the following code:

        fileHandle = await window.showSaveFilePicker({
          startIn: 'videos',
          suggestedName: 'newSession.webm',
          types: [{
            description: 'Video File',
            accept: { 'video/webm': ['.webm'] },
          }],
        });
        fileWritableStream = await fileHandle.createWritable();

Then, I simply feed the fileWritableStream, which is an instance of FileSystemWritableFileStream to the muxer:

 muxer1 = new WebMMuxer({
          target: fileWritableStream,
          video: {
            codec: 'V_VP9',
            width: outputW,
            height: outputH,
            frameRate: FPS
          },
          audio: {
            codec: 'A_OPUS',
            numberOfChannels: 2,
            sampleRate: 48000
          }
        });

The code above works as following: When fileHandle runs, the user is prompted to save file to local disk. When he is finished, the rest of the code starts to wrtite video chunks to the stream, and this chunks are immediatly output to the file, thus preventing accumulation of the new video chunks in memory.

Now for the problem: In chrome for Android, there is no support for window.showSaveFilePicker() nor window.showDirectoryPicker(), which means I can't prompt the user for a location to save the file and, as a consequence, I can't instantiate a FileSystemFileHandle instance, from which I could then obtain the FileSystemWritableFileStream I need. So, is there a workaround for this situation?

What I am trying to achieve is to get a FileSystemWritableFileStream instance in chrome for android, with an underlying FileSystemDirectoryHandle pointing to a folder that the user have selected.