sub: sub-filter-regex and jsre: support ass-to-plaintext

Using --sub-filter-regex-plain (default:no)

The ass-to-plaintext functionality already existed at sd_ass.c, but
it's internal and uses a private buffer type, so a trivial utility
wrapper was added with standard char*/bstr interface.

The plaintext can be multi-line, and the multi-line regexp flag is now
always set, but only affects plaintext (the ASS source is one line).

1 files changed, 7 insertions, 1 deletions

diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index c540400c74..c08161f338 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -2804,7 +2804,7 @@ Subtitles
 
     List items are matched in order. If a regular expression matches, the
     process is stopped, and the subtitle line is discarded. The text matched
-    against is, currently, always the ``Text`` field of ASS events (if the
+    against is, by default, the ``Text`` field of ASS events (if the
     subtitle format is different, it is always converted). This may include
     formatting tags. Matching is case-insensitive, but how this is done depends
     on the libc, and most likely works in ASCII only. It does not work on
@@ -2831,6 +2831,12 @@ Subtitles
     Shares/affected-by all ``--sub-filter-regex-*`` control options (see below),
     and also experimental. Requires only JavaScript support.
 
+``--sub-filter-regex-plain=<yes|no>``
+    Whether to first convert the ASS "Text" field to plain-text (default: no).
+    This strips ASS tags and applies ASS directives, like ``\N`` to new-line.
+    If the result is multi-line then the regexp anchors ``^`` and ``$`` match
+    each line, but still any match discards all lines.
+
 ``--sub-filter-regex-warn=<yes|no>``
     Log dropped lines with warning log level, instead of verbose (default: no).
     Helpful for testing.