sub: minor refactor how video FPS for MicroDVD is set

So that the video FPs is not required at initialization, and can be set
later.

(As for whether this MicroDVD crap is worth the trouble to handle it
"correctly": MicroDVD files are unfortunately still around, and in at
least one case using the video FPS seemed to help indeed.)

player/sub.c

@@ -152,12 +152,12 @@ static void reinit_subdec(struct MPContext *mpctx, struct track *track)
     if (sub_is_initialized(dec_sub))
         return;
 
+    sub_init(dec_sub, track->demuxer, track->stream);
+
     struct sh_video *sh_video =
         mpctx->d_video ? mpctx->d_video->header->video : NULL;
-    float fps = sh_video ? sh_video->fps : 25;
-
-    sub_set_video_fps(dec_sub, fps);
-    sub_init(dec_sub, track->demuxer, track->stream);
+    double fps = sh_video ? sh_video->fps : 25;
+    sub_control(dec_sub, SD_CTRL_SET_VIDEO_DEF_FPS, &fps);
 
     // Don't do this if the file has video/audio streams. Don't do it even
     // if it has only sub streams, because reading packets will change the

sub/dec_sub.c

@@ -113,13 +113,6 @@ bool sub_is_initialized(struct dec_sub *sub)
     return r;
 }
 
-void sub_set_video_fps(struct dec_sub *sub, double fps)
-{
-    pthread_mutex_lock(&sub->lock);
-    sub->init_sd.video_fps = fps;
-    pthread_mutex_unlock(&sub->lock);
-}
-
 static int sub_init_decoder(struct dec_sub *sub, struct sd *sd)
 {
     sd->driver = NULL;

sub/dec_sub.h

@@ -8,11 +8,8 @@
 
 struct demuxer;
 struct sh_stream;
-struct ass_track;
 struct mpv_global;
 struct demux_packet;
-struct ass_library;
-struct ass_renderer;
 
 struct dec_sub;
 struct sd;
@@ -22,6 +19,7 @@ enum sd_ctrl {
     SD_CTRL_SET_VIDEO_PARAMS,
     SD_CTRL_GET_RESOLUTION,
     SD_CTRL_SET_TOP,
+    SD_CTRL_SET_VIDEO_DEF_FPS,
 };
 
 struct dec_sub *sub_create(struct mpv_global *global);
@@ -29,7 +27,6 @@ void sub_destroy(struct dec_sub *sub);
 void sub_lock(struct dec_sub *sub);
 void sub_unlock(struct dec_sub *sub);
 
-void sub_set_video_fps(struct dec_sub *sub, double fps);
 void sub_init(struct dec_sub *sub, struct demuxer *demuxer, struct sh_stream *sh);
 
 bool sub_is_initialized(struct dec_sub *sub);

sub/sd.h

@@ -19,7 +19,6 @@ struct sd {
 
     struct demuxer *demuxer;
     struct sh_stream *sh;
-    double video_fps;
 };
 
 struct sd_functions {

sub/sd_ass.c

@@ -48,7 +48,7 @@ struct sd_ass_priv {
     char last_text[500];
     struct mp_image_params video_params;
     struct mp_image_params last_params;
-    double sub_speed;
+    double sub_speed, video_fps, frame_fps;
     int64_t *seen_packets;
     int num_seen_packets;
 };
@@ -147,6 +147,24 @@ static void enable_output(struct sd *sd, bool enable)
     }
 }
 
+static void update_subtitle_speed(struct sd *sd)
+{
+    struct MPOpts *opts = sd->opts;
+    struct sd_ass_priv *ctx = sd->priv;
+    ctx->sub_speed = 1.0;
+
+    if (ctx->video_fps > 0 && ctx->frame_fps > 0) {
+        MP_VERBOSE(sd, "Frame based format, dummy FPS: %f, video FPS: %f\n",
+                   ctx->frame_fps, ctx->video_fps);
+        ctx->sub_speed *= ctx->frame_fps / ctx->video_fps;
+    }
+
+    if (opts->sub_fps && ctx->video_fps)
+        ctx->sub_speed *= opts->sub_fps / ctx->video_fps;
+
+    ctx->sub_speed *= opts->sub_speed;
+}
+
 static int init(struct sd *sd)
 {
     struct MPOpts *opts = sd->opts;
@@ -187,18 +205,8 @@ static int init(struct sd *sd)
 
     mp_ass_add_default_styles(ctx->ass_track, opts);
 
-    ctx->sub_speed = 1.0;
-
-    if (sd->video_fps && sd->sh && sd->sh->sub->frame_based > 0) {
-        MP_VERBOSE(sd, "Frame based format, dummy FPS: %f, video FPS: %f\n",
-                   sd->sh->sub->frame_based, sd->video_fps);
-        ctx->sub_speed *= sd->sh->sub->frame_based / sd->video_fps;
-    }
-
-    if (opts->sub_fps && sd->video_fps)
-        ctx->sub_speed *= opts->sub_fps / sd->video_fps;
-
-    ctx->sub_speed *= opts->sub_speed;
+    ctx->frame_fps = sd->sh->sub->frame_based;
+    update_subtitle_speed(sd);
 
     enable_output(sd, true);
 
@@ -613,6 +621,10 @@ static int control(struct sd *sd, enum sd_ctrl cmd, void *arg)
     case SD_CTRL_SET_TOP:
         ctx->on_top = *(bool *)arg;
         return CONTROL_OK;
+    case SD_CTRL_SET_VIDEO_DEF_FPS:
+        ctx->video_fps = *(double *)arg;
+        update_subtitle_speed(sd);
+        return CONTROL_OK;
     default:
         return CONTROL_UNKNOWN;
     }