ffmpeg – How can I increase the size of an mp4 file to a specific value?

this is my first time here. I’m not a programmer. Question: For example, I have a video file size of 1500 mb, I need to increase the video size to 3500 mb, without changing the video quality or lenght. It is important that the final file size should have an accuracy of +- 10 mb. I thought it could be done by adding a second empty audio track using FFMPEG, but I didn’t succeed:( If anyone knows how to do this, please help

I tried to add an empty audio track lasting several hours and with a bitrate of 192 kbps using FFMPEG. However, the file size did not change much, although this audio track appeared in the VLC player, but for some reason it showed that the bitrate was 1 kbps