lavfi/subtitles: support charenc option.

doc/filters.texi

@@ -4678,6 +4678,10 @@ Set the filename of the subtitle file to read. It must be specified.
 Specify the size of the original video, the video for which the ASS file
 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
 necessary to correctly scale the fonts if the aspect ratio has been changed.
+
+@item charenc
+Set subtitles input character encoding. @code{subtitles} filter only. Only
+useful if not UTF-8.
 @end table
 
 If the first key is not specified, it is assumed that the first value

libavfilter/vf_ass.c

@@ -50,6 +50,7 @@ typedef struct {
     ASS_Renderer *renderer;
     ASS_Track    *track;
     char *filename;
+    char *charenc;
     uint8_t rgba_map[4];
     int     pix_step[4];       ///< steps per pixel for each plane of the main output
     int original_w, original_h;
@@ -253,6 +254,7 @@ AVFilter avfilter_vf_ass = {
 
 static const AVOption subtitles_options[] = {
     COMMON_OPTIONS
+    {"charenc", "set input character encoding", OFFSET(charenc), AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN, CHAR_MAX, FLAGS},
     {NULL},
 };
 
@@ -261,6 +263,7 @@ AVFILTER_DEFINE_CLASS(subtitles);
 static av_cold int init_subtitles(AVFilterContext *ctx, const char *args)
 {
     int ret, sid;
+    AVDictionary *codec_opts = NULL;
     AVFormatContext *fmt = NULL;
     AVCodecContext *dec_ctx = NULL;
     AVCodec *dec = NULL;
@@ -306,7 +309,9 @@ static av_cold int init_subtitles(AVFilterContext *ctx, const char *args)
                avcodec_get_name(dec_ctx->codec_id));
         return AVERROR(EINVAL);
     }
-    ret = avcodec_open2(dec_ctx, dec, NULL);
+    if (ass->charenc)
+        av_dict_set(&codec_opts, "sub_charenc", ass->charenc, 0);
+    ret = avcodec_open2(dec_ctx, dec, &codec_opts);
     if (ret < 0)
         goto end;
 
@@ -341,6 +346,7 @@ static av_cold int init_subtitles(AVFilterContext *ctx, const char *args)
     }
 
 end:
+    av_dict_free(&codec_opts);
     if (dec_ctx)
         avcodec_close(dec_ctx);
     if (fmt)