Fix bug in ScaleX routine which affected ratios that could span 3 pixels.

(4:3 is one of the few *not* in this category).

Allow user to override subtitle scaling via sub-aspect-ratio, 0=auto
or what we do now. 1=do nothing.

modules/codec/ogt/common.c

@@ -2,7 +2,7 @@
  * Common SVCD and VCD subtitle routines.
  *****************************************************************************
  * Copyright (C) 2003, 2004 VideoLAN
- * $Id: common.c,v 1.4 2004/01/10 13:59:25 rocky Exp $
+ * $Id: common.c,v 1.5 2004/01/11 01:54:20 rocky Exp $
  *
  * Author: Rocky Bernstein
  *   based on code from:
@@ -173,10 +173,11 @@ vout_thread_t *VCDSubFindVout( decoder_t *p_dec )
 
 
 
-/* Remove color palette by expanding pixel entries to contain the
+/**
+   Remove color palette by expanding pixel entries to contain the
    palette values. We work from the free space at the end to the
    beginning so we can expand inline.
-    */
+*/
 void
 VCDInlinePalette ( /*inout*/ uint8_t *p_dest, decoder_sys_t *p_sys,
 		   unsigned int i_height, unsigned int i_width ) 
@@ -190,12 +191,50 @@ VCDInlinePalette ( /*inout*/ uint8_t *p_dest, decoder_sys_t *p_sys,
   }
 }
 
+/**
+   Check to see if user has overridden subtitle aspect ratio. 
+   0 is returned for no override which means just counteract any
+   scaling effects.
+*/
+unsigned int 
+VCDSubGetAROverride(vlc_object_t * p_input, vout_thread_t *p_vout)
+{
+  char *psz_string = config_GetPsz( p_input, "sub-aspect-ratio" );
+
+  /* Check whether the user tried to override aspect ratio */
+  if( !psz_string ) return 0;
+
+  {
+    unsigned int i_new_aspect = 0;
+    char *psz_parser = strchr( psz_string, ':' );
+    
+    if( psz_parser )
+      {
+	*psz_parser++ = '\0';
+	i_new_aspect = atoi( psz_string ) * VOUT_ASPECT_FACTOR
+	  / atoi( psz_parser );
+      }
+    else
+      {
+	i_new_aspect = p_vout->output.i_width * VOUT_ASPECT_FACTOR
+	  * atof( psz_string )
+	  / p_vout->output.i_height;
+      }
+    
+    return i_new_aspect;
+  }
+}
+
 
-/* Scales down (reduces size) of p_dest in the x direction as 
+/**
+   Scales down (reduces size) of p_dest in the x direction as 
    determined through aspect ratio x_scale by y_scale. Scaling
    is done in place. p_spu->i_width, is updated to new width
 
    The aspect ratio is assumed to be between 1/2 and 1.
+
+   Note: the scaling truncates the new width rather than rounds it.
+   Perhaps something one might want to address.
 */
 void
 VCDSubScaleX( decoder_t *p_dec, subpicture_t *p_spu, 
@@ -208,38 +247,65 @@ VCDSubScaleX( decoder_t *p_dec, subpicture_t *p_spu,
   uint8_t *p_src2 = p_src1 + PIXEL_SIZE;
   uint8_t *p_dst  = p_src1;
   unsigned int i_new_width = (p_spu->i_width * i_scale_x) / i_scale_y ;
-  unsigned int used=0;  /* Number of bytes used up in p_src1. */
+  unsigned int i_used=0;  /* Number of bytes used up in p_src1. */
 
   dbg_print( (DECODE_DBG_CALL|DECODE_DBG_TRANSFORM) , 
 	     "aspect ratio %i:%i, Old width: %d, new width: %d", 
 	     i_scale_x, i_scale_y, p_spu->i_width, i_new_width);
+
+  if (! (i_scale_x < i_scale_y && i_scale_y < i_scale_x+i_scale_x) )
+    {
+      msg_Warn( p_dec, "Need x < y < 2x. x: %i, y: %i", i_scale_x, i_scale_y );
+      return;
+    }
   
   for ( i_row=0; i_row <= p_spu->i_height - 1; i_row++ ) {
 
-    if (used != 0) {
+    if (i_used != 0) {
       /* Discard the remaining piece of the column of the previous line*/
-      used=0;
+      i_used=0;
       p_src1 = p_src2;
       p_src2 += PIXEL_SIZE;
     }
     
     for ( i_col=0; i_col <= p_spu->i_width - 2; i_col++ ) {
       unsigned int i;
-      unsigned int w1= i_scale_x - used;
-      unsigned int w2= i_scale_y - w1;
-
-      used = w2;
-      for (i = 0; i < PIXEL_SIZE; i++ ) {
-	*p_dst = ( (*p_src1 * w1) + (*p_src2 * w2) ) / i_scale_y;
-	p_src1++; p_src2++; p_dst++;
+      unsigned int w1= i_scale_x - i_used;
+      unsigned int w2;
+      
+      if ( i_scale_y - w1 <= i_scale_x ) {
+	/* Average spans 2 pixels. */
+	w2 = i_scale_y - w1;
+
+	for (i = 0; i < PIXEL_SIZE; i++ ) {
+	  *p_dst = ( (*p_src1 * w1) + (*p_src2 * w2) ) / i_scale_y;
+	  p_src1++; p_src2++; p_dst++;
+	}
+      } else {
+	/* Average spans 3 pixels. */
+	unsigned int w0 = w1;
+	unsigned int w1 = i_scale_x;
+	uint8_t *p_src0 = p_src1;
+	w2 = i_scale_y - w0 - w1;
+	p_src1 = p_src2;
+	p_src2 += PIXEL_SIZE;
+	
+	for (i = 0; i < PIXEL_SIZE; i++ ) {
+	  *p_dst = ( (*p_src0 * w0) + (*p_src1 * w1) + (*p_src2 * w2) ) 
+		     / i_scale_y;
+	  p_src0++; p_src1++; p_src2++; p_dst++;
+	}
+	i_col++;
       }
 
-      if (i_scale_x == used) {
+      i_used = w2;
+
+      if (i_scale_x == i_used) {
 	/* End of last pixel was end of p_src2. */
 	p_src1 = p_src2;
 	p_src2 += PIXEL_SIZE;
 	i_col++;
-	used = 0;
+	i_used = 0;
       }
     }
   }
@@ -248,8 +314,8 @@ VCDSubScaleX( decoder_t *p_dec, subpicture_t *p_spu,
   if ( p_sys && p_sys->i_debug & DECODE_DBG_TRANSFORM )
   { 
     ogt_yuvt_t *p_source = (ogt_yuvt_t *) p_spu->p_sys->p_data;
-    for ( i_row=0; i_row < p_spu->i_height - 1; i_row++ ) {
-      for ( i_col=0; i_col < p_spu->i_width - 1; i_col++ ) {
+    for ( i_row=0; i_row < p_spu->i_height; i_row++ ) {
+      for ( i_col=0; i_col < p_spu->i_width; i_col++ ) {
 	printf("%1x", p_source->s.t);
 	p_source++;
       }
@@ -259,9 +325,9 @@ VCDSubScaleX( decoder_t *p_dec, subpicture_t *p_spu,
 
 }
 
-/*****************************************************************************
+/**
  * DestroySPU: subpicture destructor
- *****************************************************************************/
+ */
 void VCDSubDestroySPU( subpicture_t *p_spu )
 {
     if( p_spu->p_sys->p_input )
@@ -302,14 +368,14 @@ void VCDSubUpdateSPU( subpicture_t *p_spu, vlc_object_t *p_object )
         return;
     }
 
-    var_Get( p_object, "x-start", &val );
-    p_spu->p_sys->i_x_start = val.i_int;
-    var_Get( p_object, "y-start", &val );
-    p_spu->p_sys->i_y_start = val.i_int;
-    var_Get( p_object, "x-end", &val );
-    p_spu->p_sys->i_x_end = val.i_int;
-    var_Get( p_object, "y-end", &val );
-    p_spu->p_sys->i_y_end = val.i_int;
+    if ( VLC_SUCCESS == var_Get( p_object, "x-start", &val ) )
+      p_spu->p_sys->i_x_start = val.i_int;
+    if ( VLC_SUCCESS == var_Get( p_object, "y-start", &val ) )
+      p_spu->p_sys->i_y_start = val.i_int;
+    if ( VLC_SUCCESS == var_Get( p_object, "x-end", &val ) )
+      p_spu->p_sys->i_x_end = val.i_int;
+    if ( VLC_SUCCESS == var_Get( p_object, "y-end", &val ) )
+      p_spu->p_sys->i_y_end = val.i_int;
 
 }
 
@@ -441,3 +507,12 @@ VCDSubDumpPNG( uint8_t *p_image, decoder_t *p_dec,
   free(image_data);
 }
 #endif /*HAVE_LIBPNG*/
+
+
+/* 
+ * Local variables:
+ *  c-file-style: "gnu"
+ *  tab-width: 8
+ *  indent-tabs-mode: nil
+ * End:
+ */

modules/codec/ogt/common.h

@@ -2,7 +2,7 @@
  * Header for Common SVCD and VCD subtitle routines.
  *****************************************************************************
  * Copyright (C) 2003, 2004 VideoLAN
- * $Id: common.h,v 1.3 2004/01/03 12:54:56 rocky Exp $
+ * $Id: common.h,v 1.4 2004/01/11 01:54:20 rocky Exp $
  *
  * Author: Rocky Bernstein
  *
@@ -49,6 +49,9 @@ void           VCDInlinePalette ( /*inout*/ uint8_t *p_dest,
 void           VCDSubDumpImage( uint8_t *p_image, uint32_t i_height, 
 				uint32_t i_width );
 
+unsigned int   VCDSubGetAROverride(vlc_object_t * p_input, 
+				   vout_thread_t *p_vout);
+
 #ifdef HAVE_LIBPNG
 #include <png.h>
 void           VCDSubDumpPNG( uint8_t *p_image, decoder_t *p_dec,

modules/codec/ogt/cvd.c

@@ -2,7 +2,7 @@
  * cvd.c : CVD Subtitle decoder thread
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: cvd.c,v 1.8 2004/01/04 16:51:59 rocky Exp $
+ * $Id: cvd.c,v 1.9 2004/01/11 01:54:20 rocky Exp $
  *
  * Authors: Rocky Bernstein
  *   based on code from:
@@ -51,6 +51,10 @@ vlc_module_begin();
                   N_("set debug mask for additional debugging."),
                   N_(DEBUG_LONGTEXT), VLC_TRUE );
 
+    add_string( "sub-aspect-ratio", "", NULL,
+                SUB_ASPECT_RATIO_TEXT, SUB_ASPECT_RATIO_LONGTEXT, 
+		VLC_TRUE );
+
     add_submodule();
     set_description( _("Chaoji VCD subtitle packetizer") );
     set_capability( "packetizer", 50 );

modules/codec/ogt/cvd_parse.c

@@ -2,7 +2,7 @@
  * parse.c: Philips OGT (SVCD subtitle) packet parser
  *****************************************************************************
  * Copyright (C) 2003, 2004 VideoLAN
- * $Id: cvd_parse.c,v 1.9 2004/01/10 13:59:25 rocky Exp $
+ * $Id: cvd_parse.c,v 1.10 2004/01/11 01:54:20 rocky Exp $
  *
  * Authors: Rocky Bernstein 
  *   based on code from: 
@@ -95,11 +95,11 @@ void E_(ParseHeader)( decoder_t *p_dec, uint8_t *p_buffer, block_t *p_block )
   p_sys->metadata_offset = GETINT16(p);
   p_sys->metadata_length = p_sys->i_spu_size - p_sys->metadata_offset;
 
-  p_sys->comp_image_offset = 4;
-  p_sys->comp_image_length = p_sys->metadata_offset - p_sys->comp_image_offset;
+  p_sys->i_image_offset = 4;
+  p_sys->i_image_length = p_sys->metadata_offset - p_sys->i_image_offset;
   
   dbg_print(DECODE_DBG_PACKET, "total size: %d  image size: %d\n",
-	    p_sys->i_spu_size, p_sys->comp_image_length);
+	    p_sys->i_spu_size, p_sys->i_image_length);
 
 }
 
@@ -241,18 +241,18 @@ void E_(ParseMetaInfo)( decoder_t *p_dec  )
       
     case 0x47:
       /* offset to start of even rows of interlaced image, we correct
-	 to make it relative to comp_image_offset (usually 4) */
+	 to make it relative to i_image_offset (usually 4) */
       p_sys->first_field_offset =
-	(p[2] << 8) + p[3] - p_sys->comp_image_offset;
+	(p[2] << 8) + p[3] - p_sys->i_image_offset;
       dbg_print( DECODE_DBG_PACKET, 
 		 "first_field_offset %d", p_sys->first_field_offset);
       break;
       
     case 0x4f:
       /* offset to start of odd rows of interlaced image, we correct
-	 to make it relative to comp_image_offset (usually 4) */
+	 to make it relative to i_image_offset (usually 4) */
       p_sys->second_field_offset =
-	(p[2] << 8) + p[3] - p_sys->comp_image_offset;
+	(p[2] << 8) + p[3] - p_sys->i_image_offset;
       dbg_print( DECODE_DBG_PACKET, 
 		 "second_field_offset %d", p_sys->second_field_offset);
       break;
@@ -413,8 +413,8 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
     uint8_t i_pending = 0;     /* number of pixels to fill with 
 				  color zero 0..3 */
     ogt_color_t i_color=0;     /* current pixel color: 0..3 */
-    uint8_t *p = p_sys->subtitle_data  + p_sys->comp_image_offset;
-    uint8_t *maxp = p + p_sys->comp_image_length;
+    uint8_t *p = p_sys->subtitle_data  + p_sys->i_image_offset;
+    uint8_t *maxp = p + p_sys->i_image_length;
 
     dbg_print( (DECODE_DBG_CALL) , "width x height: %dx%d",
 	       i_width, i_height);
@@ -524,9 +524,10 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
 
     VCDInlinePalette( p_dest, p_sys, i_height, i_width );
 
-    /* The video is automatically scaled. However subtitle bitmaps
-       assume a 1:1 aspect ratio. So we need to scale to compensate for
-       or undo the effects of video output scaling. 
+    /* The video may be scaled. However subtitle bitmaps assume an 1:1
+       aspect ratio. So unless the user has specified otherwise, we
+       need to scale to compensate for or undo the effects of video
+       output scaling.
 
        Perhaps this should go in the Render routine? The advantage would
        be that it will deal with a dynamically changing aspect ratio.
@@ -534,17 +535,35 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
     */
     
     {
-      vout_thread_t *p_vout = vlc_object_find( p_spu->p_sys->p_input,
-					       VLC_OBJECT_VOUT, 
+      vlc_object_t * p_input = p_spu->p_sys->p_input;
+      vout_thread_t *p_vout = vlc_object_find( p_input, VLC_OBJECT_VOUT, 
 					       FIND_CHILD );
       unsigned int i_aspect_x, i_aspect_y;
       if (p_vout) {
-	vout_AspectRatio( p_vout->render.i_aspect, &i_aspect_x, &i_aspect_y );
-	VCDSubScaleX( p_dec, p_spu, i_aspect_y, i_aspect_x );
+        /* Check for user-configuration override. */
+        unsigned int i_new_aspect = VCDSubGetAROverride( p_input, p_vout );
+        if (i_new_aspect == VOUT_ASPECT_FACTOR) {
+          /* For scaling 1:1, nothing needs to be done. Note this means
+             subtitles will get scaled the same way the video does.
+           */
+          ;
+        } else {
+          if (0 == i_new_aspect) {
+            /* Counteract the effects of background video
+               scaling. That's why x and y are reversed from the 
+	       else branch in the call below.
+             */
+            vout_AspectRatio( p_vout->render.i_aspect, &i_aspect_y, 
+                              &i_aspect_x );
+          } else {
+            /* User knows best? */
+            vout_AspectRatio( i_new_aspect, &i_aspect_y, &i_aspect_x );
+          }
+          VCDSubScaleX( p_dec, p_spu, i_aspect_x, i_aspect_y );
+        }
       }
     }
 
-    /* To be finished...*/
     return VLC_SUCCESS;
 
 }

modules/codec/ogt/ogt.c

@@ -2,7 +2,7 @@
  * ogt.c : Overlay Graphics Text (SVCD subtitles) decoder thread
  *****************************************************************************
  * Copyright (C) 2003, 2004 VideoLAN
- * $Id: ogt.c,v 1.8 2004/01/03 12:54:56 rocky Exp $
+ * $Id: ogt.c,v 1.9 2004/01/11 01:54:20 rocky Exp $
  *
  * Author: Rocky Bernstein
  *   based on code from:
@@ -51,6 +51,10 @@ vlc_module_begin();
                   N_("set debug mask for additional debugging."),
                   N_(DEBUG_LONGTEXT), VLC_TRUE );
 
+    add_string( "sub-aspect-ratio", "", NULL,
+                SUB_ASPECT_RATIO_TEXT, SUB_ASPECT_RATIO_LONGTEXT, 
+		VLC_TRUE );
+
     add_submodule();
     set_description( _("Philips OGT (SVCD subtitle) packetizer") );
     set_capability( "packetizer", 50 );
@@ -294,3 +298,12 @@ Reassemble( decoder_t *p_dec, block_t **pp_block )
     }
     return NULL;
 }
+
+
+/* 
+ * Local variables:
+ *  c-file-style: "gnu"
+ *  tab-width: 8
+ *  indent-tabs-mode: nil
+ * End:
+ */

modules/codec/ogt/ogt_parse.c

@@ -2,7 +2,7 @@
  * Philips OGT (SVCD subtitle) packet parser
  *****************************************************************************
  * Copyright (C) 2003, 2004 VideoLAN
- * $Id: ogt_parse.c,v 1.7 2004/01/10 13:59:25 rocky Exp $
+ * $Id: ogt_parse.c,v 1.8 2004/01/11 01:54:20 rocky Exp $
  *
  * Author: Rocky Bernstein 
  *   based on code from: 
@@ -126,9 +126,9 @@ void E_(ParseHeader)( decoder_t *p_dec, uint8_t *p_buffer, block_t *p_block )
   /* Actually, this is measured against a different origin, so we have to
      adjust it */
   p_sys->second_field_offset = GETINT16(p);
-  p_sys->comp_image_offset = p - p_buffer;
-  p_sys->comp_image_length = p_sys->i_spu_size - p_sys->comp_image_offset;
-  p_sys->metadata_length   = p_sys->comp_image_offset;
+  p_sys->i_image_offset  = p - p_buffer;
+  p_sys->i_image_length  = p_sys->i_spu_size - p_sys->i_image_offset;
+  p_sys->metadata_length = p_sys->i_image_offset;
 
   if (p_sys && p_sys->i_debug & DECODE_DBG_PACKET) {
     msg_Dbg( p_dec, "x-start: %d, y-start: %d, width: %d, height %d, "
@@ -136,7 +136,7 @@ void E_(ParseHeader)( decoder_t *p_dec, uint8_t *p_buffer, block_t *p_block )
 	     p_sys->i_x_start, p_sys->i_y_start, 
 	     p_sys->i_width, p_sys->i_height, 
 	     p_sys->i_spu_size, p_sys->i_duration,
-	     p_sys->comp_image_length, p_sys->comp_image_offset);
+	     p_sys->i_image_length, p_sys->i_image_offset);
     
     for (i=0; i<4; i++) {
       msg_Dbg( p_dec, "palette[%d]= T: %2x, Y: %2x, u: %2x, v: %2x", i,
@@ -292,8 +292,8 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
     uint8_t i_pending_zero = 0;    /* number of pixels to fill with 
 				      color zero 0..3 */
     ogt_color_t i_color;           /* current pixel color: 0..3 */
-    uint8_t *p = p_sys->subtitle_data  + p_sys->comp_image_offset;
-    uint8_t *maxp = p + p_sys->comp_image_length;
+    uint8_t *p = p_sys->subtitle_data  + p_sys->i_image_offset;
+    uint8_t *maxp = p + p_sys->i_image_length;
 
     dbg_print( (DECODE_DBG_CALL) , "width x height: %dx%d ",
 	       i_width, i_height);
@@ -337,7 +337,7 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
 	  advance_color_pointer_byte;
 	}
       }
-      p = p_sys->subtitle_data + p_sys->comp_image_offset 
+      p = p_sys->subtitle_data + p_sys->i_image_offset 
 	+ p_sys->second_field_offset;
     }
 
@@ -368,10 +368,10 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
     
     VCDInlinePalette( p_dest, p_sys, i_height, i_width );
     
-
-    /* The video is automatically scaled. However subtitle bitmaps
-       assume a 1:1 aspect ratio. So we need to scale to compensate for
-       or undo the effects of video output scaling. 
+    /* The video may be scaled. However subtitle bitmaps assume an 1:1
+       aspect ratio. So unless the user has specified otherwise, we
+       need to scale to compensate for or undo the effects of video
+       output scaling.
 
        Perhaps this should go in the Render routine? The advantage would
        be that it will deal with a dynamically changing aspect ratio.
@@ -379,17 +379,43 @@ ParseImage( decoder_t *p_dec, subpicture_t * p_spu )
     */
     
     {
-      vout_thread_t *p_vout = vlc_object_find( p_spu->p_sys->p_input,
-					       VLC_OBJECT_VOUT, 
+      vlc_object_t * p_input = p_spu->p_sys->p_input;
+      vout_thread_t *p_vout = vlc_object_find( p_input, VLC_OBJECT_VOUT, 
 					       FIND_CHILD );
       unsigned int i_aspect_x, i_aspect_y;
       if (p_vout) {
-	vout_AspectRatio( p_vout->render.i_aspect, &i_aspect_x, &i_aspect_y );
-	VCDSubScaleX( p_dec, p_spu, 3, 4 );
+        /* Check for user-configuration override. */
+        unsigned int i_new_aspect = VCDSubGetAROverride( p_input, p_vout );
+        if (i_new_aspect == VOUT_ASPECT_FACTOR) {
+          /* For scaling 1:1, nothing needs to be done. Note this means
+             subtitles will get scaled the same way the video does.
+           */
+          ;
+        } else {
+          if (0 == i_new_aspect) {
+            /* Counteract the effects of background video
+               scaling. That's why x and y are reversed from the 
+	       else branch in the call below.
+             */
+            vout_AspectRatio( p_vout->render.i_aspect, &i_aspect_y, 
+                              &i_aspect_x );
+          } else {
+            /* User knows best? */
+            vout_AspectRatio( i_new_aspect, &i_aspect_x, &i_aspect_y );
+          }
+          VCDSubScaleX( p_dec, p_spu, i_aspect_x, i_aspect_y );
+        }
       }
     }
 
-
     return VLC_SUCCESS;
 }
 
+
+/* 
+ * Local variables:
+ *  c-file-style: "gnu"
+ *  tab-width: 8
+ *  indent-tabs-mode: nil
+ * End:
+ */

modules/codec/ogt/subtitle.h

@@ -2,7 +2,7 @@
  * subtitle.h : Common SVCD and CVD subtitles header
  *****************************************************************************
  * Copyright (C) 2003,2004 VideoLAN
- * $Id: subtitle.h,v 1.5 2004/01/04 22:22:10 gbazin Exp $
+ * $Id: subtitle.h,v 1.6 2004/01/11 01:54:20 rocky Exp $
  *
  * Author: Rocky Bernstein
  *   based on code from:
@@ -44,6 +44,21 @@
     "extract subtitles     64\n" \
     "misc info            128\n" )
 
+#define SUB_ASPECT_RATIO_TEXT N_("Subtitle aspect-ratio correction")
+#define SUB_ASPECT_RATIO_LONGTEXT N_(					\
+    "Use this to force the subtitle aspect ratio. If you give a null string " \
+    "the right value will be determined automatically. Usually this is what " \
+    "you want. For OGT and CVD subtitles this undoes the effect " \
+    "of the underlying video scaling. And using a value of 1 will cause " \
+    "no correction; subtitles will be scaled with the same aspect " \
+    "ratio as as the underlying video (which not correct for OGT or " \
+    "CVD subtitles). You can also force another ratio by giving a pair of " \
+    "integers x:y where y should between x and twice x. For example 4:3, or " \
+    "16:9. Alternatively, you can give a float value expressing pixel " \
+    "squareness. For example 1.25 or 1.3333 which mean the same thing as " \
+    "4:3 and 16:9 respectively." \
+    )
+
 #define DECODE_DEBUG 1
 #if DECODE_DEBUG
 #define dbg_print(mask, s, args...) \
@@ -117,9 +132,9 @@ struct decoder_sys_t
   int subtitle_data_size;	/* size of the allocated subtitle_data */
 
   /* Move into subpicture_sys_t? */
-  uint16_t comp_image_offset;	/* offset from subtitle_data to compressed
+  uint16_t i_image_offset;	/* offset from subtitle_data to compressed
 				   image data */
-  int comp_image_length;	/* size of the compressed image data */
+  int i_image_length;	        /* size of the compressed image data */
   int first_field_offset;       /* offset of even raster lines. Used
 				   only for CVD.
 				 */