image-compression - 画像とビデオの圧縮

Question

RAR アルゴリズムに類似した圧縮プログラムは何ですか? 動画 (avi など) や画像 (jpg など) の圧縮に興味があります。

Winrar は、avi ビデオ (1 フレーム/秒) を元のサイズの .88% に縮小しました (つまり、49.8MB だったものが 442KB に減少しました)。圧縮は 4 秒以内に完了しました。

だから、私は同様の（オープンな）アルゴリズムを探しています。減圧時間は気にしません。

Answer 1

Compressing "already compressed" formats are meaningless. Because, you can't get anything further. Even some archivers refuse to compress such files and stores as it is. If you really need to compress image and video files you need to "recompress" them. It's not meant to simply convert file format. I mean decode image or video file to some extent (not require to fully decoding), and apply your specific models instead of formats' model with a stronger entropy coder. There are several good attempts for such usages. Here is a few list:

1. PackJPG: Open source and fast performer JPEG recompressor.
2. Dell's Experimental MPEG1 and MPEG2 Compressor: Closed source and proprietry. But, you can at least test that experimental compressor strength.
3. Precomp: Closed source free software (but, it'll be open in near future). It recompress GIF, BZIP2, JPEG (with PackJPG) and Deflate (only generated with ZLIB library) streams.

Note that recompression is usually very time consuming process. Because, you have to ensure bit-identical restoration. Some programs even check every possible parameter to ensure stability (like Precomp). Also, their models have to be more and more complex to gain something negligible.

Answer 2

(jpg) のような圧縮形式は、エントロピーに達しているため、実際には圧縮できません。ただし、bmp、wav、avi などの非圧縮形式は可能です。

LZMAを見てください