vo_rpi: redraw subtitles only on change

Since vo_rpi uses MMAL for video output, which is completely
independent from the GLES overlay, we can just not redraw the
GLES screen if subtitles do not change.

(As a furhter optimization, the dispmanx overlay could be removed
if nothing is visible. But I'm not sure if adding and removing the
overlay frequently is a good idea for performance, so this could
just as well go the other way.)

3 files changed, 33 insertions, 4 deletions

diff --git a/video/out/gl_osd.c b/video/out/gl_osd.c
index c346a3e630..0307904c25 100644
--- a/video/out/gl_osd.c
+++ b/video/out/gl_osd.c
@@ -78,6 +78,7 @@ struct mpgl_osd_part {
     int w, h;
     GLuint buffer;
     int num_subparts;
+    int prev_num_subparts;
     struct sub_bitmap *subparts;
     struct vertex *vertices;
     struct bitmap_packer *packer;
@@ -93,6 +94,7 @@ struct mpgl_osd {
     const struct osd_fmt_entry *fmt_table;
     bool formats[SUBBITMAP_COUNT];
     struct gl_vao vao;
+    int64_t change_counter;
     // temporary
     int stereo_mode;
     int display_size[2];
@@ -288,6 +290,7 @@ static void gen_osd_cb(void *pctx, struct sub_bitmaps *imgs)
             osd->packer->count = 0;
 
         osd->change_id = imgs->change_id;
+        ctx->change_counter += 1;
     }
     osd->num_subparts = osd->packer->count;
 
@@ -420,4 +423,18 @@ void mpgl_osd_generate(struct mpgl_osd *ctx, struct mp_osd_res res, double pts,
 
     osd_draw(ctx->osd, s_res, pts, draw_flags, ctx->formats, gen_osd_cb, ctx);
     ctx->stereo_mode = stereo_mode;
+
+    // Parts going away does not necessarily result in gen_osd_cb() being called
+    // (not even with num_parts==0), so check this separately.
+    for (int n = 0; n < MAX_OSD_PARTS; n++) {
+        struct mpgl_osd_part *part = ctx->parts[n];
+        if (part->num_subparts !=  part->prev_num_subparts)
+            ctx->change_counter += 1;
+        part->prev_num_subparts = part->num_subparts;
+    }
+}
+
+int64_t mpgl_get_change_counter(struct mpgl_osd *ctx)
+{
+    return ctx->change_counter;
 }
diff --git a/video/out/gl_osd.h b/video/out/gl_osd.h
index 130008a58d..e00565aad7 100644
--- a/video/out/gl_osd.h
+++ b/video/out/gl_osd.h
@@ -17,5 +17,6 @@ void mpgl_osd_generate(struct mpgl_osd *ctx, struct mp_osd_res res, double pts,
 enum sub_bitmap_format mpgl_osd_get_part_format(struct mpgl_osd *ctx, int index);
 struct gl_vao *mpgl_osd_get_vao(struct mpgl_osd *ctx);
 void mpgl_osd_draw_part(struct mpgl_osd *ctx, int vp_w, int vp_h, int index);
+int64_t mpgl_get_change_counter(struct mpgl_osd *ctx);
 
 #endif
diff --git a/video/out/vo_rpi.c b/video/out/vo_rpi.c
index 95627d4073..f3dfab3af6 100644
--- a/video/out/vo_rpi.c
+++ b/video/out/vo_rpi.c
@@ -56,6 +56,7 @@ struct priv {
     struct mp_egl_rpi egl;
     struct gl_shader_cache *sc;
     struct mpgl_osd *osd;
+    int64_t osd_change_counter;
 
     MMAL_COMPONENT_T *renderer;
     bool renderer_enabled;
@@ -117,6 +118,16 @@ static void update_osd(struct vo *vo)
 
     mpgl_osd_generate(p->osd, p->osd_res, p->osd_pts, 0, 0);
 
+    int64_t osd_change_counter = mpgl_get_change_counter(p->osd);
+    if (p->osd_change_counter == osd_change_counter) {
+        p->skip_osd = true;
+        return;
+    }
+    p->osd_change_counter = osd_change_counter;
+
+    p->egl.gl->ClearColor(0, 0, 0, 0);
+    p->egl.gl->Clear(GL_COLOR_BUFFER_BIT);
+
     for (int n = 0; n < MAX_OSD_PARTS; n++) {
         enum sub_bitmap_format fmt = mpgl_osd_get_part_format(p->osd, n);
         if (!fmt)
@@ -331,11 +342,9 @@ static void draw_frame(struct vo *vo, struct vo_frame *frame)
     // Redraw only if the OSD has meaningfully changed, which we assume it
     // hasn't when a frame is merely repeated for display sync.
     p->skip_osd = !frame->redraw && frame->repeat;
-    if (!p->skip_osd && p->egl.gl) {
-        p->egl.gl->ClearColor(0, 0, 0, 0);
-        p->egl.gl->Clear(GL_COLOR_BUFFER_BIT);
+
+    if (!p->skip_osd && p->egl.gl)
         update_osd(vo);
-    }
 
     p->display_synced = frame->display_synced;
 
@@ -519,8 +528,10 @@ static int control(struct vo *vo, uint32_t request, void *data)
     case VOCTRL_SET_PANSCAN:
         if (p->renderer_enabled)
             resize(vo);
+        vo->want_redraw = true;
         return VO_TRUE;
     case VOCTRL_REDRAW_FRAME:
+        p->osd_change_counter = -1;
         update_osd(vo);
         return VO_TRUE;
     case VOCTRL_SCREENSHOT_WIN: