Custom paragraph-start and paragraph-separate for editing *.srt files

Question

I'm having some trouble coming up with regular expressions for variables paragraph-start and paragraph-separate to do what I want (to be defined shortly). I'm editing *.srt files (subtitles for school lectures) and trying to set my variables so that M - } and M - { take me up and back one block of text for editing. The file has the following format:

1
00:00:16,040 --> 00:00:23,130
Some text here that marks the beginning       <--
of a block.

2
00:00:23,390 --> 00:00:28,230
(Speaker): And some more                      <--

3
00:00:28,230 --> 00:00:32,350
text here that also marks the                 <--
beginning of another block. There
could be multiple sentences in here.

I want to set variables paragraph-start and paragraph-separate in such a way that M-{ and M-} (paragraph back and forward) take me between the beginning of the lines marked with <--.

I tried to set paragraph-separate to ".*-->.*" (since the arrow never appears in the subtitles text) and paragraph-start to match any after this line, but M-} always seems to place me on the timestamps line (the one including the -->), although I want to go to the line after it.

Any ideas what I'm doing wrong and how I can set the variables paragraph-start and paragraph-separate appropriately?

Answer 1

The following code will probably do what you want.

Note that it will change globally M-{ and M-}.

I would use an hydra for this (assuming that I would use also other functions during file editing).

(defun adl/srt-backward-paragraph ()
  (interactive)
  (backward-paragraph 2)
  (if (= (point) (point-min))
      (next-line 2)    
    (next-line 3)))

(defun adl/srt-forward-paragraph ()
  (interactive)
  (forward-paragraph)
  (while (= (char-after) 10) (next-line))
  (next-line 2))


(global-set-key (kbd "M-{") 'adl/srt-backward-paragraph)
(global-set-key (kbd "M-}") 'adl/srt-forward-paragraph)