Untested RGBA blending in I420, RV24 and RV32.
authorAntoine Cellerier <dionoea@videolan.org>
Fri, 30 Mar 2007 17:29:41 +0000 (17:29 +0000)
committerAntoine Cellerier <dionoea@videolan.org>
Fri, 30 Mar 2007 17:29:41 +0000 (17:29 +0000)
modules/video_filter/blend.c

index f372247..86f91dd 100644 (file)
@@ -1,10 +1,11 @@
 /*****************************************************************************
  * blend.c: alpha blend 2 pictures together
  *****************************************************************************
- * Copyright (C) 2003 the VideoLAN team
+ * Copyright (C) 2003-2007 the VideoLAN team
  * $Id$
  *
- * Author: Gildas Bazin <gbazin@videolan.org>
+ * Authors: Gildas Bazin <gbazin@videolan.org>
+ *          Antoine Cellerier <dionoea @t videolan dot org>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -43,6 +44,7 @@ static int  OpenFilter ( vlc_object_t * );
 static void CloseFilter( vlc_object_t * );
 
 /* TODO i_alpha support for BlendR16 */
+/* YUVA */
 static void Blend( filter_t *, picture_t *, picture_t *, picture_t *,
                    int, int, int );
 static void BlendI420( filter_t *, picture_t *, picture_t *, picture_t *,
@@ -53,6 +55,8 @@ static void BlendR24( filter_t *, picture_t *, picture_t *, picture_t *,
                       int, int, int, int, int );
 static void BlendYUVPacked( filter_t *, picture_t *, picture_t *, picture_t *,
                             int, int, int, int, int );
+
+/* YUVP */
 static void BlendPalI420( filter_t *, picture_t *, picture_t *, picture_t *,
                           int, int, int, int, int );
 static void BlendPalYUVPacked( filter_t *, picture_t *, picture_t *, picture_t *,
@@ -60,6 +64,12 @@ static void BlendPalYUVPacked( filter_t *, picture_t *, picture_t *, picture_t *
 static void BlendPalRV( filter_t *, picture_t *, picture_t *, picture_t *,
                         int, int, int, int, int );
 
+/* RGBA */
+static void BlendRGBAI420( filter_t *, picture_t *, picture_t *, picture_t *,
+                           int, int, int, int, int );
+static void BlendRGBAR24( filter_t *, picture_t *, picture_t *, picture_t *,
+                          int, int, int, int, int );
+
 /*****************************************************************************
  * Module descriptor
  *****************************************************************************/
@@ -79,16 +89,26 @@ static int OpenFilter( vlc_object_t *p_this )
 
     /* Check if we can handle that format.
      * We could try to use a chroma filter if we can't. */
-    if( ( p_filter->fmt_in.video.i_chroma != VLC_FOURCC('Y','U','V','A') &&
-          p_filter->fmt_in.video.i_chroma != VLC_FOURCC('Y','U','V','P') ) ||
-        ( p_filter->fmt_out.video.i_chroma != VLC_FOURCC('I','4','2','0') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('Y','U','Y','2') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('Y','V','1','2') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('U','Y','V','Y') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('Y','V','Y','U') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('R','V','1','6') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('R','V','2','4') &&
-          p_filter->fmt_out.video.i_chroma != VLC_FOURCC('R','V','3','2') ) )
+    int in_chroma = p_filter->fmt_in.video.i_chroma;
+    int out_chroma = p_filter->fmt_out.video.i_chroma;
+    if(
+      ( ( in_chroma  != VLC_FOURCC('Y','U','V','A') &&
+          in_chroma  != VLC_FOURCC('Y','U','V','P') ) ||
+        ( out_chroma != VLC_FOURCC('I','4','2','0') &&
+          out_chroma != VLC_FOURCC('Y','U','Y','2') &&
+          out_chroma != VLC_FOURCC('Y','V','1','2') &&
+          out_chroma != VLC_FOURCC('U','Y','V','Y') &&
+          out_chroma != VLC_FOURCC('Y','V','Y','U') &&
+          out_chroma != VLC_FOURCC('R','V','1','6') &&
+          out_chroma != VLC_FOURCC('R','V','2','4') &&
+          out_chroma != VLC_FOURCC('R','V','3','2') ) )
+      &&
+      ( ( in_chroma  != VLC_FOURCC('R','G','B','A') ) ||
+        ( out_chroma != VLC_FOURCC('I','4','2','0') &&
+          out_chroma != VLC_FOURCC('Y','V','1','2') &&
+          out_chroma != VLC_FOURCC('R','V','2','4') &&
+          out_chroma != VLC_FOURCC('R','V','3','2' ) ) )
+      )
     {
         return VLC_EGENERIC;
     }
@@ -112,6 +132,17 @@ static int OpenFilter( vlc_object_t *p_this )
     return VLC_SUCCESS;
 }
 
+/*****************************************************************************
+ * CloseFilter: clean up the filter
+ *****************************************************************************/
+static void CloseFilter( vlc_object_t *p_this )
+{
+    filter_t *p_filter = (filter_t*)p_this;
+    filter_sys_t *p_sys = p_filter->p_sys;
+
+    free( p_sys );
+}
+
 /****************************************************************************
  * Blend: the whole thing
  ****************************************************************************
@@ -131,68 +162,118 @@ static void Blend( filter_t *p_filter, picture_t *p_dst,
 
     if( i_width <= 0 || i_height <= 0 ) return;
 
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','A') &&
-        ( p_filter->fmt_out.video.i_chroma == VLC_FOURCC('I','4','2','0') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('Y','V','1','2') ) )
+    switch( p_filter->fmt_in.video.i_chroma )
     {
-        BlendI420( p_filter, p_dst, p_dst_orig, p_src,
-                   i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
-    }
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','A') &&
-        ( p_filter->fmt_out.video.i_chroma == VLC_FOURCC('Y','U','Y','2') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('U','Y','V','Y') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('Y','V','Y','U') ) )
-    {
-        BlendYUVPacked( p_filter, p_dst, p_dst_orig, p_src,
-                   i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
-    }
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','A') &&
-        p_filter->fmt_out.video.i_chroma == VLC_FOURCC('R','V','1','6') )
-    {
-        BlendR16( p_filter, p_dst, p_dst_orig, p_src,
-                  i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
-    }
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','A') &&
-        ( p_filter->fmt_out.video.i_chroma == VLC_FOURCC('R','V','2','4') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('R','V','3','2') ) )
-    {
-        BlendR24( p_filter, p_dst, p_dst_orig, p_src,
-                  i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
-    }
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','P') &&
-        ( p_filter->fmt_out.video.i_chroma == VLC_FOURCC('I','4','2','0') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('Y','V','1','2') ) )
-    {
-        BlendPalI420( p_filter, p_dst, p_dst_orig, p_src,
-                      i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
-    }
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','P') &&
-        ( p_filter->fmt_out.video.i_chroma == VLC_FOURCC('Y','U','Y','2') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('U','Y','V','Y') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('Y','V','Y','U') ) )
-    {
-        BlendPalYUVPacked( p_filter, p_dst, p_dst_orig, p_src,
-                      i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
-    }
-    if( p_filter->fmt_in.video.i_chroma == VLC_FOURCC('Y','U','V','P') &&
-        ( p_filter->fmt_out.video.i_chroma == VLC_FOURCC('R','V','1','6') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('R','V','2','4') ||
-          p_filter->fmt_out.video.i_chroma == VLC_FOURCC('R','V','3','2') ) )
-    {
-        BlendPalRV( p_filter, p_dst, p_dst_orig, p_src,
-                    i_x_offset, i_y_offset, i_width, i_height, i_alpha );
-        return;
+        case VLC_FOURCC('Y','U','V','A'):
+            switch( p_filter->fmt_out.video.i_chroma )
+            {
+                case VLC_FOURCC('I','4','2','0'):
+                case VLC_FOURCC('Y','V','1','2'):
+                    BlendI420( p_filter, p_dst, p_dst_orig, p_src,
+                               i_x_offset, i_y_offset,
+                               i_width, i_height, i_alpha );
+                    return;
+                case VLC_FOURCC('Y','U','Y','2'):
+                case VLC_FOURCC('U','Y','V','Y'):
+                case VLC_FOURCC('Y','V','Y','U'):
+                    BlendYUVPacked( p_filter, p_dst, p_dst_orig, p_src,
+                                    i_x_offset, i_y_offset,
+                                    i_width, i_height, i_alpha );
+                    return;
+                case VLC_FOURCC('R','V','1','6'):
+                    BlendR16( p_filter, p_dst, p_dst_orig, p_src,
+                              i_x_offset, i_y_offset,
+                              i_width, i_height, i_alpha );
+                    return;
+                case VLC_FOURCC('R','V','2','4'):
+                case VLC_FOURCC('R','V','3','2'):
+                    BlendR24( p_filter, p_dst, p_dst_orig, p_src,
+                              i_x_offset, i_y_offset,
+                              i_width, i_height, i_alpha );
+                    return;
+            }
+        case VLC_FOURCC('Y','U','V','P'):
+            switch( p_filter->fmt_out.video.i_chroma )
+            {
+                case VLC_FOURCC('I','4','2','0'):
+                case VLC_FOURCC('Y','V','1','2'):
+                    BlendPalI420( p_filter, p_dst, p_dst_orig, p_src,
+                                  i_x_offset, i_y_offset,
+                                  i_width, i_height, i_alpha );
+                    return;
+                case VLC_FOURCC('Y','U','Y','2'):
+                case VLC_FOURCC('U','Y','V','Y'):
+                case VLC_FOURCC('Y','V','Y','U'):
+                    BlendPalYUVPacked( p_filter, p_dst, p_dst_orig, p_src,
+                                       i_x_offset, i_y_offset,
+                                       i_width, i_height, i_alpha );
+                    return;
+                case VLC_FOURCC('R','V','1','6'):
+                case VLC_FOURCC('R','V','2','4'):
+                case VLC_FOURCC('R','V','3','2'):
+                    BlendPalRV( p_filter, p_dst, p_dst_orig, p_src,
+                                i_x_offset, i_y_offset,
+                                i_width, i_height, i_alpha );
+                    return;
+            }
+        case VLC_FOURCC('R','G','B','A'):
+            switch( p_filter->fmt_out.video.i_chroma )
+            {
+                case VLC_FOURCC('I','4','2','0'):
+                case VLC_FOURCC('Y','V','1','2'):
+                    BlendRGBAI420( p_filter, p_dst, p_dst_orig, p_src,
+                                   i_x_offset, i_y_offset,
+                                   i_width, i_height, i_alpha );
+                    return;
+                case VLC_FOURCC('R','V','2','4'):
+                case VLC_FOURCC('R','V','3','2'):
+                    BlendRGBAR24( p_filter, p_dst, p_dst_orig, p_src,
+                                  i_x_offset, i_y_offset,
+                                  i_width, i_height, i_alpha );
+                    return;
+            }
     }
 
     msg_Dbg( p_filter, "no matching alpha blending routine" );
 }
 
+/***********************************************************************
+ * Utils
+ ***********************************************************************/
+static inline void yuv_to_rgb( int *r, int *g, int *b,
+                               uint8_t y1, uint8_t u1, uint8_t v1 )
+{
+    /* macros used for YUV pixel conversions */
+#   define SCALEBITS 10
+#   define ONE_HALF  (1 << (SCALEBITS - 1))
+#   define FIX(x)    ((int) ((x) * (1<<SCALEBITS) + 0.5))
+#   define CLAMP( x ) (((x) > 255) ? 255 : ((x) < 0) ? 0 : (x));
+
+    int y, cb, cr, r_add, g_add, b_add;
+
+    cb = u1 - 128;
+    cr = v1 - 128;
+    r_add = FIX(1.40200*255.0/224.0) * cr + ONE_HALF;
+    g_add = - FIX(0.34414*255.0/224.0) * cb
+            - FIX(0.71414*255.0/224.0) * cr + ONE_HALF;
+    b_add = FIX(1.77200*255.0/224.0) * cb + ONE_HALF;
+    y = (y1 - 16) * FIX(255.0/219.0);
+    *r = CLAMP((y + r_add) >> SCALEBITS);
+    *g = CLAMP((y + g_add) >> SCALEBITS);
+    *b = CLAMP((y + b_add) >> SCALEBITS);
+}
+
+static inline void rgb_to_yuv( uint8_t *y, uint8_t *u, uint8_t *v,
+                               int r, int g, int b )
+{
+    *y = ( ( (  66 * r + 129 * g +  25 * b + 128 ) >> 8 ) + 16 );
+    *u =   ( ( -38 * r -  74 * g + 112 * b + 128 ) >> 8 ) + 128 ;
+    *v =   ( ( 112 * r -  94 * g -  18 * b + 128 ) >> 8 ) + 128 ;
+}
+
+/***********************************************************************
+ * YUVA
+ ***********************************************************************/
 static void BlendI420( filter_t *p_filter, picture_t *p_dst,
                        picture_t *p_dst_orig, picture_t *p_src,
                        int i_x_offset, int i_y_offset,
@@ -310,29 +391,6 @@ static void BlendI420( filter_t *p_filter, picture_t *p_dst,
     return;
 }
 
-static inline void yuv_to_rgb( int *r, int *g, int *b,
-                               uint8_t y1, uint8_t u1, uint8_t v1 )
-{
-    /* macros used for YUV pixel conversions */
-#   define SCALEBITS 10
-#   define ONE_HALF  (1 << (SCALEBITS - 1))
-#   define FIX(x)    ((int) ((x) * (1<<SCALEBITS) + 0.5))
-#   define CLAMP( x ) (((x) > 255) ? 255 : ((x) < 0) ? 0 : (x));
-
-    int y, cb, cr, r_add, g_add, b_add;
-
-    cb = u1 - 128;
-    cr = v1 - 128;
-    r_add = FIX(1.40200*255.0/224.0) * cr + ONE_HALF;
-    g_add = - FIX(0.34414*255.0/224.0) * cb
-            - FIX(0.71414*255.0/224.0) * cr + ONE_HALF;
-    b_add = FIX(1.77200*255.0/224.0) * cb + ONE_HALF;
-    y = (y1 - 16) * FIX(255.0/219.0);
-    *r = CLAMP((y + r_add) >> SCALEBITS);
-    *g = CLAMP((y + g_add) >> SCALEBITS);
-    *b = CLAMP((y + b_add) >> SCALEBITS);
-}
-
 static void BlendR16( filter_t *p_filter, picture_t *p_dst_pic,
                       picture_t *p_dst_orig, picture_t *p_src,
                       int i_x_offset, int i_y_offset,
@@ -620,7 +678,7 @@ static void BlendYUVPacked( filter_t *p_filter, picture_t *p_dst_pic,
                         i_u = (p_src2_u[i_x]+p_src2_u[i_x+1])>>1;
                         i_v = (p_src2_v[i_x]+p_src2_v[i_x+1])>>1;
                     }
-                    else 
+                    else
                     {
                         i_u = p_src2_u[i_x];
                         i_v = p_src2_v[i_x];
@@ -642,6 +700,9 @@ static void BlendYUVPacked( filter_t *p_filter, picture_t *p_dst_pic,
     return;
 }
 
+/***********************************************************************
+ * YUVP
+ ***********************************************************************/
 static void BlendPalI420( filter_t *p_filter, picture_t *p_dst,
                           picture_t *p_dst_orig, picture_t *p_src,
                           int i_x_offset, int i_y_offset,
@@ -848,7 +909,7 @@ static void BlendPalYUVPacked( filter_t *p_filter, picture_t *p_dst_pic,
                         i_u = (p_pal[p_src2[i_x]][1] + p_pal[p_src2[i_x+1]][1]) >> 1;
                         i_v = (p_pal[p_src2[i_x]][2] + p_pal[p_src2[i_x+1]][2]) >> 1;
                     }
-                    else 
+                    else
                     {
                         i_u = p_pal[p_src2[i_x]][1];
                         i_v = p_pal[p_src2[i_x]][2];
@@ -970,13 +1031,200 @@ static void BlendPalRV( filter_t *p_filter, picture_t *p_dst_pic,
     return;
 }
 
-/*****************************************************************************
- * CloseFilter: clean up the filter
- *****************************************************************************/
-static void CloseFilter( vlc_object_t *p_this )
+/***********************************************************************
+ * RGBA
+ ***********************************************************************/
+static void BlendRGBAI420( filter_t *p_filter, picture_t *p_dst,
+                           picture_t *p_dst_orig, picture_t *p_src,
+                           int i_x_offset, int i_y_offset,
+                           int i_width, int i_height, int i_alpha )
 {
-    filter_t *p_filter = (filter_t*)p_this;
-    filter_sys_t *p_sys = p_filter->p_sys;
+    int i_src1_pitch, i_src2_pitch, i_dst_pitch, i_src_pix_pitch;
+    uint8_t *p_src1_y, *p_dst_y;
+    uint8_t *p_src1_u, *p_dst_u;
+    uint8_t *p_src1_v, *p_dst_v;
+    uint8_t *p_src2;
+    int i_x, i_y, i_trans;
+    uint8_t y, u, v;
 
-    free( p_sys );
+    vlc_bool_t b_even_scanline = i_y_offset % 2;
+
+    i_dst_pitch = p_dst->p[Y_PLANE].i_pitch;
+    p_dst_y = p_dst->p[Y_PLANE].p_pixels + i_x_offset +
+              p_filter->fmt_out.video.i_x_offset +
+              p_dst->p[Y_PLANE].i_pitch *
+              ( i_y_offset + p_filter->fmt_out.video.i_y_offset );
+    p_dst_u = p_dst->p[U_PLANE].p_pixels + i_x_offset/2 +
+              p_filter->fmt_out.video.i_x_offset/2 +
+              ( i_y_offset + p_filter->fmt_out.video.i_y_offset ) / 2 *
+              p_dst->p[U_PLANE].i_pitch;
+    p_dst_v = p_dst->p[V_PLANE].p_pixels + i_x_offset/2 +
+              p_filter->fmt_out.video.i_x_offset/2 +
+              ( i_y_offset + p_filter->fmt_out.video.i_y_offset ) / 2 *
+              p_dst->p[V_PLANE].i_pitch;
+
+    i_src1_pitch = p_dst_orig->p[Y_PLANE].i_pitch;
+    p_src1_y = p_dst_orig->p[Y_PLANE].p_pixels + i_x_offset +
+               p_filter->fmt_out.video.i_x_offset +
+               p_dst_orig->p[Y_PLANE].i_pitch *
+               ( i_y_offset + p_filter->fmt_out.video.i_y_offset );
+    p_src1_u = p_dst_orig->p[U_PLANE].p_pixels + i_x_offset/2 +
+               p_filter->fmt_out.video.i_x_offset/2 +
+               ( i_y_offset + p_filter->fmt_out.video.i_y_offset ) / 2 *
+               p_dst_orig->p[U_PLANE].i_pitch;
+    p_src1_v = p_dst_orig->p[V_PLANE].p_pixels + i_x_offset/2 +
+               p_filter->fmt_out.video.i_x_offset/2 +
+               ( i_y_offset + p_filter->fmt_out.video.i_y_offset ) / 2 *
+               p_dst_orig->p[V_PLANE].i_pitch;
+
+    i_src_pix_pitch = p_src->p->i_pixel_pitch;
+    i_src2_pitch = p_src->p->i_pitch;
+    p_src2 = p_src->p->p_pixels +
+             p_filter->fmt_in.video.i_x_offset * i_src2_pitch +
+             p_src->p->i_pitch * p_filter->fmt_in.video.i_y_offset;
+
+
+#define MAX_TRANS 255
+#define TRANS_BITS  8
+
+    /* Draw until we reach the bottom of the subtitle */
+    for( i_y = 0; i_y < i_height; i_y++,
+         p_dst_y += i_dst_pitch, p_src1_y += i_src1_pitch,
+         p_dst_u += b_even_scanline ? i_dst_pitch/2 : 0,
+         p_src1_u += b_even_scanline ? i_src1_pitch/2 : 0,
+         p_dst_v += b_even_scanline ? i_dst_pitch/2 : 0,
+         p_src1_v += b_even_scanline ? i_src1_pitch/2 : 0,
+         p_src2 += i_src2_pitch )
+    {
+        b_even_scanline = !b_even_scanline;
+
+        /* Draw until we reach the end of the line */
+        for( i_x = 0; i_x < i_width; i_x++ )
+        {
+#define     R         ( p_src2[i_x * i_src_pix_pitch + 0] )
+#define     G         ( p_src2[i_x * i_src_pix_pitch + 1] )
+#define     B         ( p_src2[i_x * i_src_pix_pitch + 2] )
+            i_trans = ( p_src2[i_x * i_src_pix_pitch + 3] * i_alpha ) / 255;
+            if( !i_trans )
+            {
+                /* Completely transparent. Don't change pixel */
+                continue;
+            }
+            else if( i_trans == MAX_TRANS )
+            {
+                /* Completely opaque. Completely overwrite underlying pixel */
+                rgb_to_yuv( &y, &u, &v, R, G, B );
+                p_dst_y[i_x] = y;
+
+                if( b_even_scanline && i_x % 2 == 0 )
+                {
+                    p_dst_u[i_x/2] = u;
+                    p_dst_v[i_x/2] = v;
+                }
+                continue;
+            }
+
+            /* Blending */
+            rgb_to_yuv( &y, &u, &v, R, G, B );
+            p_dst_y[i_x] = ( (uint16_t)y * i_trans +
+                (uint16_t)p_src1_y[i_x] * (MAX_TRANS - i_trans) )
+                >> TRANS_BITS;
+
+            if( b_even_scanline && i_x % 2 == 0 )
+            {
+                p_dst_u[i_x/2] = ( (uint16_t)u * i_trans +
+                (uint16_t)p_src1_u[i_x/2] * (MAX_TRANS - i_trans) )
+                >> TRANS_BITS;
+                p_dst_v[i_x/2] = ( (uint16_t)v * i_trans +
+                (uint16_t)p_src1_v[i_x/2] * (MAX_TRANS - i_trans) )
+                >> TRANS_BITS;
+            }
+#undef      R
+#undef      G
+#undef      B
+        }
+    }
+
+#undef MAX_TRANS
+#undef TRANS_BITS
+
+    return;
+}
+
+static void BlendRGBAR24( filter_t *p_filter, picture_t *p_dst_pic,
+                          picture_t *p_dst_orig, picture_t *p_src,
+                          int i_x_offset, int i_y_offset,
+                          int i_width, int i_height, int i_alpha )
+{
+    int i_src1_pitch, i_src2_pitch, i_dst_pitch;
+    uint8_t *p_dst, *p_src1, *p_src2;
+    int i_x, i_y, i_pix_pitch, i_trans, i_src_pix_pitch;
+
+    i_pix_pitch = p_dst_pic->p->i_pixel_pitch;
+    i_dst_pitch = p_dst_pic->p->i_pitch;
+    p_dst = p_dst_pic->p->p_pixels + i_x_offset * i_pix_pitch +
+            p_filter->fmt_out.video.i_x_offset * i_pix_pitch +
+            p_dst_pic->p->i_pitch *
+            ( i_y_offset + p_filter->fmt_out.video.i_y_offset );
+
+    i_src1_pitch = p_dst_orig->p->i_pitch;
+    p_src1 = p_dst_orig->p->p_pixels + i_x_offset * i_pix_pitch +
+             p_filter->fmt_out.video.i_x_offset * i_pix_pitch +
+             p_dst_orig->p->i_pitch *
+             ( i_y_offset + p_filter->fmt_out.video.i_y_offset );
+
+    i_src_pix_pitch = p_src->p->i_pixel_pitch;
+    i_src2_pitch = p_src->p->i_pitch;
+    p_src2 = p_src->p->p_pixels +
+             p_filter->fmt_in.video.i_x_offset * i_pix_pitch +
+             p_src->p->i_pitch * p_filter->fmt_in.video.i_y_offset;
+
+#define MAX_TRANS 255
+#define TRANS_BITS  8
+
+    /* Draw until we reach the bottom of the subtitle */
+    for( i_y = 0; i_y < i_height; i_y++,
+         p_dst += i_dst_pitch, p_src1 += i_src1_pitch, p_src2 += i_src2_pitch )
+    {
+        /* Draw until we reach the end of the line */
+        for( i_x = 0; i_x < i_width; i_x++ )
+        {
+#define     R         ( p_src2[i_x * i_src_pix_pitch + 0] )
+#define     G         ( p_src2[i_x * i_src_pix_pitch + 1] )
+#define     B         ( p_src2[i_x * i_src_pix_pitch + 2] )
+            i_trans = ( p_src2[i_x * i_src_pix_pitch + 3] * i_alpha ) / 255;
+            if( !i_trans )
+            {
+                /* Completely transparent. Don't change pixel */
+                continue;
+            }
+            else if( i_trans == MAX_TRANS )
+            {
+                /* Completely opaque. Completely overwrite underlying pixel */
+                p_dst[i_x * i_pix_pitch + 0] = R;
+                p_dst[i_x * i_pix_pitch + 1] = G;
+                p_dst[i_x * i_pix_pitch + 2] = B;
+                continue;
+            }
+
+            /* Blending */
+            p_dst[i_x * i_pix_pitch + 0] = ( R * i_trans +
+                (uint16_t)p_src1[i_x * i_pix_pitch + 0] *
+                (MAX_TRANS - i_trans) ) >> TRANS_BITS;
+            p_dst[i_x * i_pix_pitch + 1] = ( G * i_trans +
+                (uint16_t)p_src1[i_x * i_pix_pitch + 1] *
+                (MAX_TRANS - i_trans) ) >> TRANS_BITS;
+            p_dst[i_x * i_pix_pitch + 2] = ( B * i_trans +
+                (uint16_t)p_src1[i_x * i_pix_pitch + 2] *
+                (MAX_TRANS - i_trans) ) >> TRANS_BITS;
+#undef      R
+#undef      G
+#undef      B
+        }
+    }
+
+#undef MAX_TRANS
+#undef TRANS_BITS
+
+    return;
 }