mplayer 1.0rc4 fails to build on MacOSX Lion. Lion ships with libpng 1.5. This fix allows mplayer 1.0rc4 to work with libpng 1.5. The diff was taken from r32840 on mplayer svn

vd_mpng.c.diff

diff --git a/libmpcodecs/vd_mpng.c b/libmpcodecs/vd_mpng.c
index 13dcfdb..c430566 100644
--- a/libmpcodecs/vd_mpng.c
+++ b/libmpcodecs/vd_mpng.c
@@ -74,7 +74,7 @@ static int    pngLength;
 
 static void pngReadFN( png_structp pngstr,png_bytep buffer,png_size_t size )
 {
- char * p = pngstr->io_ptr;
+ char * p = png_get_io_ptr(pngstr);
  if(size>pngLength-pngPointer && pngLength>=pngPointer) size=pngLength-pngPointer;
  fast_memcpy( buffer,(char *)&p[pngPointer],size );
  pngPointer+=size;
@@ -90,6 +90,7 @@ static mp_image_t* decode(sh_video_t *sh,void* data,int len,int flags){
     png_uint_32     png_width=0,png_height=0;
     int             depth,color;
     png_uint_32     i;
+    png_byte        color_type;
     mp_image_t* mpi;
 
     int cols;
@@ -111,7 +112,9 @@ static mp_image_t* decode(sh_video_t *sh,void* data,int len,int flags){
  png_get_IHDR( png,info,&png_width,&png_height,&depth,&color,NULL,NULL,NULL );
  png_set_bgr( png );
 
- switch( info->color_type ) {
+ color_type=png_get_color_type(png, info);
+
+ switch( color_type ) {
    case PNG_COLOR_TYPE_GRAY_ALPHA:
       mp_msg( MSGT_DECVIDEO,MSGL_INFO,"Sorry gray scaled png with alpha channel not supported at moment.\n" );
       break;
@@ -128,7 +131,7 @@ static mp_image_t* decode(sh_video_t *sh,void* data,int len,int flags){
       out_fmt=IMGFMT_BGR24;
       break;
    default:
-      mp_msg( MSGT_DECVIDEO,MSGL_INFO,"Sorry, unsupported PNG colorspace: %d.\n" ,info->color_type);
+      mp_msg( MSGT_DECVIDEO,MSGL_INFO,"Sorry, unsupported PNG colorspace: %d.\n" ,color_type);
  }
 
  // (re)init libvo if image parameters changed (width/height/colorspace)

Very helpful, thanks!