stream_lavf: use metadata-codepage option for codepage conversion

a343666ab5 made demux options public, so
we can take advantage of that here as well. This lets users guess the
codepage if the stream doesn't use UTF-8 characters. Fixes #8844.

stream/stream_lavf.c

@@ -26,6 +26,8 @@
 #include "common/msg.h"
 #include "common/tags.h"
 #include "common/av_common.h"
+#include "demux/demux.h"
+#include "misc/charset_conv.h"
 #include "misc/thread_tools.h"
 #include "stream.h"
 #include "options/m_config.h"
@@ -403,7 +405,21 @@ static struct mp_tags *read_icy(stream_t *s)
         packet = bstr_cut(packet, i + head.len);
         int end = bstr_find(packet, bstr0("\';"));
         packet = bstr_splice(packet, 0, end);
+
+        bool allocated = false;
+        struct demux_opts *opts = mp_get_config_group(NULL, s->global, &demux_conf);
+        const char *charset = mp_charset_guess(s, s->log, packet, opts->meta_cp, 0);
+        if (charset && !mp_charset_is_utf8(charset)) {
+            bstr conv = mp_iconv_to_utf8(s->log, packet, charset, 0);
+            if (conv.start && conv.start != packet.start) {
+                allocated = true;
+                packet = conv;
+            }
+        }
         mp_tags_set_bstr(res, bstr0("icy-title"), packet);
+        talloc_free(opts);
+        if (allocated)
+            talloc_free(packet.start);
     }
 
     av_opt_set(avio, "icy_metadata_packet", "-", AV_OPT_SEARCH_CHILDREN);