[FFmpeg-user] How to copy all of 5 audio streams to mp4 file

Ted Park kumowoon1025 at gmail.com
Tue Feb 19 18:14:18 EET 2019

> Yes, I know, and for monochrome images it compresses much better. But
> I'm wondering about the scrambled content and the huge amout of PNG
> files in the ripped data, so it seems to me, that each subtitle pic
> becomes somehow decrypted from many PNG fragments which unfortunately
> fill 10 % of the entire stream.

JPEG isn’t a bitmap format. And those png’s aren’t encrypted, they are regular (more or less) black and white bitmaps. On a commercial pressed dvd it would have been kind a wireframe that the subtitles are built on using color info from the program it’s in. So ~10% isn’t too bad when it’s pulled out as something independently decodable. You can ocr the text, but if you are wanting to archive the original bitmap based subs, not much that can be done. There’s no easy way to weave it back in as subpicture either, not a reversible process.

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