demux: change the default of metadata-codepage to auto

There's really no reason not to do this especially since sub-codepage
already defaults to auto. Also change logging in charset_conv since
telling us that the data is UTF-8 if the passed codepage value is "auto"
or "utf-8" is really not useful information (that's the expectation).

DOCS/interface-changes.rst

@@ -97,6 +97,7 @@ Interface changes
     - add `--window-affinity` option
     - `--config-dir` no longer forces cache and state files to also reside in there
     - deprecate `--demuxer-cue-codepage` in favor of `--metadata-codepage`
+    - change the default of `metadata-codepage` to `auto`
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

DOCS/man/options.rst

@@ -7315,10 +7315,9 @@ Miscellaneous
     filters.
 
 ``--metadata-codepage=<codepage>``
-    Codepage for various input metadata (default: ``utf-8``). This affects how
-    file tags, chapter titles, etc. are interpreted. You can for example set
-    this to ``auto`` to enable autodetection of the codepage. (This is not the
-    default because non-UTF-8 codepages are an obscure fringe use-case.)
+    Codepage for various input metadata (default: ``auto``). This affects how
+    file tags, chapter titles, etc. are interpreted. In most cases, this merely
+    evaluates to UTF-8 as non-UTF-8 codepages are obscure.
 
     See ``--sub-codepage`` option on how codepages are specified and further
     details regarding autodetection and codepage conversion. (The underlying

demux/demux.c

@@ -142,7 +142,7 @@ const struct m_sub_options demux_conf = {
             [STREAM_VIDEO] = 1,
             [STREAM_AUDIO] = 10,
         },
-        .meta_cp = "utf-8",
+        .meta_cp = "auto",
     },
     .get_sub_options = get_demux_sub_opts,
 };

misc/charset_conv.c

@@ -114,7 +114,8 @@ const char *mp_charset_guess(void *talloc_ctx, struct mp_log *log,  bstr buf,
 
     int r = bstr_validate_utf8(buf);
     if (r >= 0 || (r > -8 && (flags & MP_ICONV_ALLOW_CUTOFF))) {
-        mp_verbose(log, "Data looks like UTF-8, ignoring user-provided charset.\n");
+        if (strcmp(user_cp, "auto") != 0 && !mp_charset_is_utf8(user_cp))
+            mp_verbose(log, "Data looks like UTF-8, ignoring user-provided charset.\n");
         return "utf-8";
     }