How encode to UTF-8 content of buffer?

Question

Windows 10, Emacs 25.1

When I open file that not encoding in UTF-8 I get the next incorrect result:

I try by command set-buffe-file-coding-system but it not help.

And here result:

As you can see this command not help.

To fix this I need to encoding content to UTF-8.

Note: If I open this file by Notepad++ than it show correct:

Here test case when I apply function "find-file-with-coding-system" with KOI8-R of @Tobias, but it not help.

Also I try by emacs-Q, but result same.

Here base64-encode-region part of my file:

MQowMDowMDo0MCwzODMgLS0+IDAwOjAwOjQzLDkyOArR5eLl8Cwg5+Dv4OQsIP7jLCDk7urr4OTi
4Ony5S4KCjIKMDA6MDA6NTAsMzkzIC0tPiAwMDowMDo1Miw1MjcKyuDq4u4g6PHq4Pgg5OAg6uDm
5fg/CgozCjAwOjAwOjUyLDY4NyAtLT4gMDA6MDA6NTYsMTU1Csrg6uLu8u4g6uDn4PUuCgo0CjAw
OjAwOjU2LDMxNSAtLT4gMDA6MDE6MDAsMjg1Cs3g5P/i4Pgg8eUg5OAg7vbl6+XlLgoKNQowMDow
MTowMCw0NDUgLS0+IDAwOjAxOjAzLDE2MgrS7uLgIO3lIOUg5O7x8uDy+vft7i4KCjYKMDA6MDE6
MDMsMzIyIC0tPiAwMDowMTowNSw2MjMKwOruIPLoIOTw5ezl+OUuLi4KLSDK4PDrLg==

How I can do this?

Answer 1

Emacs decodes a text file with an appropriate coding system when you open it with find-file. If you have to tell emacs for some reason what coding system it should use for decoding the file you should do so before you open the file.

You can set the coding system for the next command with Options -> Multilingual Environment -> Set Coding Systems -> For Next Command. That next command can be find-file for your file subtitle.srt.

The file is then read with the coding system of your choice.

If you often need to open files with specified coding system you can also use the following command. Paste the code into your init file and restart emacs. Afterwards you can use the new menu item Find File With Coding System in the File menu.

(defun find-file-with-coding-system (file coding-system)
  "Find FILE with CODING-SYSTEM."
  (interactive (list
                (read-file-name "File Name:")
                (read-coding-system "Coding System:")))
  (let (buf (coding-system-for-read coding-system))
    (if (setq buf
              (catch :exit
                (while (setq buf (find-buffer-visiting file))
                  (if (y-or-n-p (format "Kill buffer \"%s\" visiting file \"%s\"?" buf file))
                      (kill-buffer buf)
                    (throw :exit buf)))))
        (error "Buffer \"%s\" is still visiting \"%s\". In that case `find-file-with-coding-system' does not work as expected." buf file)
      (find-file file))))

(require 'easymenu)
(easy-menu-add-item menu-bar-file-menu nil ["Find File With Coding System" find-file-with-coding-system t] "Filesets")

Note that normally the coding system of the file is automatically detected. For newly created buffers and for buffers where the coding system cannot be uniquely identified the option default-buffer-file-coding-system determines which coding system is preferred.

As far as I know there is no predefined function changing the buffer file coding-system for decoding without re-reading the file.

That is what you actually asked me in one of your comments:

And the last question: Is it possible to correct decode file AFTER open?

Maybe, that function is not provided since the decoding is not necessarily injective and the translation of the coding system can fail.

Nevertheless, the next lisp function tries to change the coding system for decoding without re-reading the file.

(defun translate-buffer-encoding (target-encoding &optional source-encoding)
  "Translate buffer encoding from SOURCE-ENCODING to TARGET-ENCODING."
  (interactive (list (read-non-nil-coding-system "Target encoding:")))
  (unless source-encoding
    (setq source-encoding buffer-file-coding-system))
  (encode-coding-region (point-min)
            (point-max)
            source-encoding)
  (decode-coding-region (point-min)
            (point-max)
            target-encoding)
  (set-buffer-file-coding-system target-encoding))

Answer 2

Your problem has nothing to do with utf-8. Your screenshot of Notepad++ indicates Windows-1251 encoding for that file as you can see at the right end of the status line of Notepad++. Therefore you have to select windows-1251 and not utf-8 as coding system. You can use my other answer for a first try with windows-1251 encoding.

Note, that 8-bit encodings can seldom be differentiated. So emacs has (almost) no chance to detect windows-1251 without further information. (I used the word almost here since there would always be a text analysis as a last resort.)

It seems that Notepad++ is setup for a Russian language environment. If you want to permanently setup your emacs for Windows-1252 you can consult the page on emacs Russification at emacswiki.

I cite here the most important settings for your init file.

(set-language-environment 'Cyrillic-KOI8)
(setq default-buffer-file-coding-system 'koi8-r)
(prefer-coding-system 'koi8-r)

(setq-default coding-system-for-read 'koi8-r)
;; (setq-default coding-system-for-write 'koi8-r) ;; Maybe not!
(codepage-setup 1251)
(define-coding-system-alias 'windows-1251 'cp1251)