Attempt to stop subtitles going off screen in some formats, when

width and height are specified in the subtitles stream. This may
result in chunkier text in some instances, but it should get it
back on screen at least. Will look into smoothing it out next.

src/video_output/vout_subpictures.c

@@ -524,6 +524,17 @@ void spu_RenderSubpictures( spu_t *p_spu, video_format_t *p_fmt,
         int pi_subpic_x[ SCALE_SIZE ];
         int k;
 
+        /* If the source video and subtitles stream agree on the size of
+         * the video then disregard all further references to the subtitle
+         * stream.
+         */
+        if( ( i_source_video_height == p_subpic->i_original_picture_height ) &&
+            ( i_source_video_width  == p_subpic->i_original_picture_width ) )
+        {
+            p_subpic->i_original_picture_height = 0;
+            p_subpic->i_original_picture_width = 0;
+        }
+
         for( k = 0; k < SCALE_SIZE ; k++ )
             pi_subpic_x[ k ] = p_subpic->i_x;
 
@@ -599,12 +610,25 @@ void spu_RenderSubpictures( spu_t *p_spu, video_format_t *p_fmt,
             if( p_text_region && 
                 ( ( p_text_region->i_align & SUBPICTURE_RENDERED ) == 0 ) )
             {
-                p_spu->p_text->fmt_out.video.i_width =
-                    p_spu->p_text->fmt_out.video.i_visible_width =
-                    p_fmt->i_width;
-                p_spu->p_text->fmt_out.video.i_height =
-                    p_spu->p_text->fmt_out.video.i_visible_height =
-                    p_fmt->i_height;
+                if( (p_subpic->i_original_picture_height > 0) &&
+                    (p_subpic->i_original_picture_width  > 0) )
+                {
+                    p_spu->p_text->fmt_out.video.i_width =
+                        p_spu->p_text->fmt_out.video.i_visible_width =
+                        p_subpic->i_original_picture_width;
+                    p_spu->p_text->fmt_out.video.i_height =
+                        p_spu->p_text->fmt_out.video.i_visible_height =
+                        p_subpic->i_original_picture_height;
+                }
+                else
+                {
+                    p_spu->p_text->fmt_out.video.i_width =
+                        p_spu->p_text->fmt_out.video.i_visible_width =
+                        p_fmt->i_width;
+                    p_spu->p_text->fmt_out.video.i_height =
+                        p_spu->p_text->fmt_out.video.i_visible_height =
+                        p_fmt->i_height;
+                }
             }
         }
 
@@ -618,18 +642,24 @@ void spu_RenderSubpictures( spu_t *p_spu, video_format_t *p_fmt,
             pi_scale_height[ SCALE_TEXT ]    = ( p_fmt->i_height * 1000 ) /
                                           p_spu->p_text->fmt_out.video.i_height;
         }
+        /* If we have an explicit size plane to render to, then turn off
+         * the fontsize rescaling.
+         */
+        if( (p_subpic->i_original_picture_height > 0) &&
+            (p_subpic->i_original_picture_width  > 0) )
+        {
+            i_scale_width_orig  = 1000;
+            i_scale_height_orig = 1000;
+        }
 
         for( k = 0; k < SCALE_SIZE ; k++ )
         {
+            /* Case of both width and height being specified has been dealt with
+             * above by instead rendering to an output pane of the explicit
+             * dimensions specified - we don't need to scale it.
+             */
             if( (p_subpic->i_original_picture_height > 0) &&
-                (p_subpic->i_original_picture_width  > 0) )
-            {
-                pi_scale_width[ k ]  = pi_scale_width[ k ]  * i_source_video_width /
-                                 p_subpic->i_original_picture_width;
-                pi_scale_height[ k ] = pi_scale_height[ k ] * i_source_video_height /
-                                 p_subpic->i_original_picture_height;
-            }
-            else if( p_subpic->i_original_picture_height > 0 )
+                (p_subpic->i_original_picture_width  <= 0) )
             {
                 pi_scale_height[ k ] = pi_scale_height[ k ] * i_source_video_height /
                                  p_subpic->i_original_picture_height;
@@ -638,6 +668,7 @@ void spu_RenderSubpictures( spu_t *p_spu, video_format_t *p_fmt,
             }
         }
 
+
         /* Set default subpicture aspect ratio */
         if( p_region && p_region->fmt.i_aspect &&
             ( !p_region->fmt.i_sar_num || !p_region->fmt.i_sar_den ) )