increased precission of s_xinc s_xinc2 (needed for the mmx2 bugfix)

moved mmx variables to top to avoid alignment issues
mmx2 code should work fine now if and only if the input width is %16=0 and the output width is %32=0
reordered some code (5% faster with a simply -benchmark)
first line bug fixed (i hope i didnt introduce any new bugs with that ...)
changed a lot of the vertical scale setup code, i hope i fixed something and didnt mess it up :)
a few known bugs left (rightmost line is wrong)
MMX2 code will only be used for upscaling & acceptable width´s
16bit dithering can be disabled


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@2265 b3059339-0415-0410-9bf9-f77b7e298cf2

2 files changed, 542 insertions, 412 deletions

diff --git a/postproc/swscale.c b/postproc/swscale.c
index b02fe41152..049099abcb 100644
--- a/postproc/swscale.c
+++ b/postproc/swscale.c
@@ -1,28 +1,29 @@
 
 // Software scaling and colorspace conversion routines for MPlayer
 
+// Orginal C implementation by ?
+// current version mostly by Michael Niedermayer (michaelni@gmx.at)
+
 #include <inttypes.h>
 #include "../config.h"
 
-#undef HAVE_MMX2 //code is buggy
+//#undef HAVE_MMX2
 //#undef HAVE_MMX
+//#undef ARCH_X86
+#define DITHER16BPP
+#define ALT_ERROR
 
 #define RET 0xC3 //near return opcode
+/*
+NOTES
 
-// temporary storage for 4 yuv lines:
-// 16bit for now (mmx likes it more compact)
-static uint16_t pix_buf_y[4][2048];
-static uint16_t pix_buf_uv[2][2048*2];
+known BUGS with known cause (no bugreports please!)
+line at the right (c,asm and mmx2)
+code reads 1 sample too much (might cause a sig11)
 
-// clipping helper table for C implementations:
-static unsigned char clip_table[768];
-
-// yuv->rgb conversion tables:
-static    int yuvtab_2568[256];
-static    int yuvtab_3343[256];
-static    int yuvtab_0c92[256];
-static    int yuvtab_1a1e[256];
-static    int yuvtab_40cf[256];
+TODO
+check alignment off everything
+*/
 
 static uint64_t yCoeff=    0x2568256825682568LL;
 static uint64_t ubCoeff=   0x3343334333433343LL;
@@ -46,11 +47,27 @@ static uint64_t g16Mask=   0x07E007E007E007E0LL;
 static uint64_t r16Mask=   0xF800F800F800F800LL;
 static uint64_t temp0;
 
+
+// temporary storage for 4 yuv lines:
+// 16bit for now (mmx likes it more compact)
+static uint16_t pix_buf_y[4][2048];
+static uint16_t pix_buf_uv[2][2048*2];
+
+// clipping helper table for C implementations:
+static unsigned char clip_table[768];
+
+// yuv->rgb conversion tables:
+static    int yuvtab_2568[256];
+static    int yuvtab_3343[256];
+static    int yuvtab_0c92[256];
+static    int yuvtab_1a1e[256];
+static    int yuvtab_40cf[256];
+
+
 static uint8_t funnyYCode[10000];
 static uint8_t funnyUVCode[10000];
 
 
-
 // *** bilinear scaling and yuv->rgb conversion of yv12 slices:
 // *** Note: it's called multiple times while decoding a frame, first time y==0
 // *** Designed to upscale, but may work for downscale too.
@@ -64,27 +81,43 @@ void SwScale_YV12slice_brg24(unsigned char* srcptr[],int stride[], int y, int h,
 //static int s_yinc=(vo_dga_src_height<<16)/vo_dga_vp_height;
 //static int s_xinc=(vo_dga_src_width<<8)/vo_dga_vp_width;
 
-unsigned int s_xinc2=s_xinc>>1;
+unsigned int s_xinc2;
 
-static int s_srcypos;
+static int s_srcypos; // points to the dst Pixels center in the source (0 is the center of pixel 0,0 in src)
 static int s_ypos;
+
+// last horzontally interpolated lines, used to avoid unnecessary calculations
 static int s_last_ypos;
+static int s_last_y1pos;
+
 static int static_dstw;
 
 #ifdef HAVE_MMX2
+// used to detect a horizontal size change
 static int old_dstw= -1;
 static int old_s_xinc= -1;
+
+// difference between the requested xinc and the required one for the mmx2 routine
+static int s_xinc_diff=0;
+static int s_xinc2_diff=0;
 #endif
+int canMMX2BeUsed;
 
-s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each other
+// we need that precission at least for the mmx2 code
+s_xinc*= 256;
+s_xinc2=s_xinc>>1;
+canMMX2BeUsed= (s_xinc <= 0x10000 && (dstw&31)==0) ? 1 : 0;
 
   if(y==0){
-      s_srcypos=-2*s_yinc;
-      s_ypos=-2;
-      s_last_ypos=-2;
+      s_srcypos= s_yinc/2 - 0x8000;
+      s_ypos=0;
+
+      // force calculation of the horizontal interpolation of the first line
+      s_last_ypos=-99;
+      s_last_y1pos=-99;
 #ifdef HAVE_MMX2
 // cant downscale !!!
-	if(old_s_xinc != s_xinc || old_dstw!=dstw)
+	if((old_s_xinc != s_xinc || old_dstw!=dstw) && canMMX2BeUsed)
 	{
 		uint8_t *fragment;
 		int imm8OfPShufW1;
@@ -102,32 +135,30 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 
 		//code fragment
 
-//		fragmentLength=0;
-//		printf("%d, %d\n", fragmentLength,imm8OfPShufW1);
-
 		asm volatile(
 			"jmp 9f				\n\t"
 		// Begin
 			"0:				\n\t"
-			"movq (%%esi, %%ebx), %%mm0	\n\t" //FIXME Alignment
+			"movq (%%esi), %%mm0		\n\t" //FIXME Alignment
 			"movq %%mm0, %%mm1		\n\t"
 			"psrlq $8, %%mm0		\n\t"
 			"punpcklbw %%mm7, %%mm1	\n\t"
+			"movq %%mm2, %%mm3		\n\t"
 			"punpcklbw %%mm7, %%mm0	\n\t"
+			"addw %%bx, %%cx		\n\t" //2*xalpha += (4*s_xinc)&0xFFFF
 			"pshufw $0xFF, %%mm1, %%mm1	\n\t"
 			"1:				\n\t"
+			"adcl %%edx, %%esi		\n\t" //xx+= (4*s_xinc)>>16 + carry
 			"pshufw $0xFF, %%mm0, %%mm0	\n\t"
 			"2:				\n\t"
+			"psrlw $9, %%mm3		\n\t"
 			"psubw %%mm1, %%mm0		\n\t"
-			"psraw $1, %%mm0		\n\t"
-			"pmullw %%mm2, %%mm0		\n\t"
+			"pmullw %%mm3, %%mm0		\n\t"
+			"paddw %%mm6, %%mm2		\n\t" // 2*alpha += xpos&0xFFFF
 			"psllw $7, %%mm1		\n\t"
 			"paddw %%mm1, %%mm0		\n\t"
-			"movq %%mm0, (%%edi, %%eax)	\n\t"
-			"paddb %%mm6, %%mm2		\n\t" // 2*alpha += xpos&0xFF
 
-			"addb %%ch, %%cl		\n\t" //2*xalpha += (4*s_xinc)&0xFF
-			"adcl %%edx, %%ebx		\n\t" //xx+= (4*s_xinc)>>8 + carry
+			"movq %%mm0, (%%edi, %%eax)	\n\t"
 
 			"addl $8, %%eax			\n\t"
 		// End
@@ -147,17 +178,28 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		);
 
 		xpos= xx=xalpha= 0;
-		//FIXME choose size and or xinc so that they fit exactly
+
+		/* choose xinc so that all 8 parts fit exactly
+		   Note: we cannot use just 1 part because it would not fit in the code cache */
+		s_xinc2_diff= -((((s_xinc2*(dstw/8))&0xFFFF))/(dstw/8))+10;
+//		s_xinc_diff= -((((s_xinc*(dstw/8))&0xFFFF))/(dstw/8));
+#ifdef ALT_ERROR
+		s_xinc2_diff+= ((0x10000/(dstw/8)));
+#endif
+		s_xinc_diff= s_xinc2_diff*2;
+
+		s_xinc2+= s_xinc2_diff;
+		s_xinc+= s_xinc_diff;
 		for(i=0; i<dstw/8; i++)
 		{
-			int xx=xpos>>8;
+			int xx=xpos>>16;
 
 			if((i&3) == 0)
 			{
 				int a=0;
-				int b=((xpos+s_xinc)>>8) - xx;
-				int c=((xpos+s_xinc*2)>>8) - xx;
-				int d=((xpos+s_xinc*3)>>8) - xx;
+				int b=((xpos+s_xinc)>>16) - xx;
+				int c=((xpos+s_xinc*2)>>16) - xx;
+				int d=((xpos+s_xinc*3)>>16) - xx;
 
 				memcpy(funnyYCode + fragmentLength*i/4, fragment, fragmentLength);
 
@@ -174,14 +216,14 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		//FIXME choose size and or xinc so that they fit exactly
 		for(i=0; i<dstw/8; i++)
 		{
-			int xx=xpos>>8;
+			int xx=xpos>>16;
 
 			if((i&3) == 0)
 			{
 				int a=0;
-				int b=((xpos+s_xinc2)>>8) - xx;
-				int c=((xpos+s_xinc2*2)>>8) - xx;
-				int d=((xpos+s_xinc2*3)>>8) - xx;
+				int b=((xpos+s_xinc2)>>16) - xx;
+				int c=((xpos+s_xinc2*2)>>16) - xx;
+				int d=((xpos+s_xinc2*3)>>16) - xx;
 
 				memcpy(funnyUVCode + fragmentLength*i/4, fragment, fragmentLength);
 
@@ -197,86 +239,117 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 
 
 	}
-#endif
+
+	if(canMMX2BeUsed)
+	{
+		s_xinc+= s_xinc_diff;
+		s_xinc2+= s_xinc2_diff;
+	}
+#endif // HAVE_MMX2
   } // reset counters
 
   while(1){
     unsigned char *dest=dstptr+dststride*s_ypos;
-    int y0=2+(s_srcypos>>16);
-    int y1=1+(s_srcypos>>17);
+    int y0=(s_srcypos + 0xFFFF)>>16;  // first luminance source line number below the dst line
+	// points to the dst Pixels center in the source (0 is the center of pixel 0,0 in src)
+    int srcuvpos= s_srcypos + s_yinc/2 - 0x8000;
+    int y1=(srcuvpos + 0x1FFFF)>>17; // first chrominance source line number below the dst line
     int yalpha=(s_srcypos&0xFFFF)>>7;
     int yalpha1=yalpha^511;
-    int uvalpha=((s_srcypos>>1)&0xFFFF)>>7;
+    int uvalpha=(srcuvpos&0x1FFFF)>>8;
     int uvalpha1=uvalpha^511;
-    uint16_t *buf0=pix_buf_y[y0&3];
-    uint16_t *buf1=pix_buf_y[((y0+1)&3)];
-    uint16_t *uvbuf0=pix_buf_uv[y1&1];
-    uint16_t *uvbuf1=pix_buf_uv[(y1&1)^1];
+    uint16_t *buf0=pix_buf_y[y0&1];		// top line of the interpolated slice
+    uint16_t *buf1=pix_buf_y[((y0+1)&1)];	// bottom line of the interpolated slice
+    uint16_t *uvbuf0=pix_buf_uv[y1&1];		// top line of the interpolated slice
+    uint16_t *uvbuf1=pix_buf_uv[(y1+1)&1];	// bottom line of the interpolated slice
     int i;
 
-    if(y0>=y+h) break;
+    // if this is before the first line than use only the first src line
+    if(y0==0) buf0= buf1;
+    if(y1==0) uvbuf0= uvbuf1; // yes we do have to check this, its not the same as y0==0
+
+    if(y0>=y+h) break; // FIXME wrong, skips last lines, but they are dupliactes anyway
+
+    // if this is after the last line than use only the last src line
+    if(y0>=y+h)
+    {
+	buf1= buf0;
+	s_last_ypos=y0;
+    }
+    if(y1>=(y+h)/2)
+    {
+	uvbuf1= uvbuf0;
+	s_last_y1pos=y1;
+    }
+
 
     s_ypos++; s_srcypos+=s_yinc;
 
+    //only interpolate the src line horizontally if we didnt do it allready
     if(s_last_ypos!=y0){
       unsigned char *src=srcptr[0]+(y0-y)*stride[0];
       unsigned int xpos=0;
       s_last_ypos=y0;
       // *** horizontal scale Y line to temp buffer
-      // this loop should be rewritten in MMX assembly!!!!
-#ifdef HAVE_MMX2
-	asm volatile(
-		"pxor %%mm7, %%mm7		\n\t"
-		"pxor %%mm2, %%mm2		\n\t" // 2*xalpha
-		"movd %5, %%mm6			\n\t" // s_xinc&0xFF
-		"punpcklwd %%mm6, %%mm6		\n\t"
-		"punpcklwd %%mm6, %%mm6		\n\t"
-		"movq %%mm6, %%mm2		\n\t"
-		"psllq $16, %%mm2		\n\t"
-		"paddb %%mm6, %%mm2		\n\t"
-		"psllq $16, %%mm2		\n\t"
-		"paddb %%mm6, %%mm2		\n\t"
-		"psllq $16, %%mm2		\n\t" //0,t,2t,3t		t=s_xinc&0xFF
-		"movq %%mm2, temp0		\n\t"
-		"movd %4, %%mm6			\n\t" //(s_xinc*4)&0xFF
-		"punpcklwd %%mm6, %%mm6		\n\t"
-		"punpcklwd %%mm6, %%mm6		\n\t"
-		"xorl %%eax, %%eax		\n\t" // i
-		"xorl %%ebx, %%ebx		\n\t" // xx
-		"movl %0, %%esi			\n\t" // src
-		"movl %1, %%edi			\n\t" // buf1
-		"movl %3, %%edx			\n\t" // (s_xinc*4)>>8
-		"xorl %%ecx, %%ecx		\n\t"
-		"movb %4, %%ch			\n\t" // (s_xinc*4)&0xFF
-//	"int $3\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyYCode			\n\t"
-		:: "m" (src), "m" (buf1), "m" (dstw), "m" ((s_xinc*4)>>8),
-		  "m" ((s_xinc*4)&0xFF), "m" (s_xinc&0xFF)
-		: "%eax", "%ebx", "%ecx", "%edx", "%esi", "%edi"
-	);
+#ifdef ARCH_X86
 
-#elif defined (ARCH_X86)
+#ifdef HAVE_MMX2
+	if(canMMX2BeUsed)
+	{
+		asm volatile(
+			"pxor %%mm7, %%mm7		\n\t"
+			"pxor %%mm2, %%mm2		\n\t" // 2*xalpha
+			"movd %5, %%mm6			\n\t" // s_xinc&0xFFFF
+			"punpcklwd %%mm6, %%mm6		\n\t"
+			"punpcklwd %%mm6, %%mm6		\n\t"
+			"movq %%mm6, %%mm2		\n\t"
+			"psllq $16, %%mm2		\n\t"
+			"paddw %%mm6, %%mm2		\n\t"
+			"psllq $16, %%mm2		\n\t"
+			"paddw %%mm6, %%mm2		\n\t"
+			"psllq $16, %%mm2		\n\t" //0,t,2t,3t		t=s_xinc&0xFF
+			"movq %%mm2, temp0		\n\t"
+			"movd %4, %%mm6			\n\t" //(s_xinc*4)&0xFFFF
+			"punpcklwd %%mm6, %%mm6		\n\t"
+			"punpcklwd %%mm6, %%mm6		\n\t"
+			"xorl %%eax, %%eax		\n\t" // i
+			"movl %0, %%esi			\n\t" // src
+			"movl %1, %%edi			\n\t" // buf1
+			"movl %3, %%edx			\n\t" // (s_xinc*4)>>16
+			"xorl %%ecx, %%ecx		\n\t"
+			"xorl %%ebx, %%ebx		\n\t"
+			"movw %4, %%bx			\n\t" // (s_xinc*4)&0xFFFF
+	//	"int $3\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			"movq temp0, %%mm2		\n\t"
+			"xorl %%ecx, %%ecx		\n\t"
+			"call funnyYCode			\n\t"
+			:: "m" (src), "m" (buf1), "m" (dstw), "m" ((s_xinc*4)>>16),
+			"m" ((s_xinc*4)&0xFFFF), "m" (s_xinc&0xFFFF)
+			: "%eax", "%ebx", "%ecx", "%edx", "%esi", "%edi"
+		);
+	}
+	else
+	{
+#endif
 	//NO MMX just normal asm ... FIXME try/write funny MMX2 variant
 	//FIXME add prefetch
 	asm volatile(
@@ -288,24 +361,24 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		"movzbl 1(%0, %%ebx), %%esi	\n\t" //src[xx+1]
 		"subl %%edi, %%esi		\n\t" //src[xx+1] - src[xx]
 		"imull %%ecx, %%esi		\n\t" //(src[xx+1] - src[xx])*2*xalpha
-		"shll $8, %%edi			\n\t"
+		"shll $16, %%edi		\n\t"
 		"addl %%edi, %%esi		\n\t" //src[xx+1]*2*xalpha + src[xx]*(1-2*xalpha)
 		"movl %1, %%edi			\n\t"
-		"shrl $1, %%esi			\n\t"
+		"shrl $9, %%esi			\n\t"
 		"movw %%si, (%%edi, %%eax, 2)	\n\t"
-		"addb %4, %%cl			\n\t" //2*xalpha += s_xinc&0xFF
+		"addw %4, %%cx			\n\t" //2*xalpha += s_xinc&0xFF
 		"adcl %3, %%ebx			\n\t" //xx+= s_xinc>>8 + carry
 
 		"movzbl (%0, %%ebx), %%edi	\n\t" //src[xx]
 		"movzbl 1(%0, %%ebx), %%esi	\n\t" //src[xx+1]
 		"subl %%edi, %%esi		\n\t" //src[xx+1] - src[xx]
 		"imull %%ecx, %%esi		\n\t" //(src[xx+1] - src[xx])*2*xalpha
-		"shll $8, %%edi			\n\t"
+		"shll $16, %%edi		\n\t"
 		"addl %%edi, %%esi		\n\t" //src[xx+1]*2*xalpha + src[xx]*(1-2*xalpha)
 		"movl %1, %%edi			\n\t"
-		"shrl $1, %%esi			\n\t"
+		"shrl $9, %%esi			\n\t"
 		"movw %%si, 2(%%edi, %%eax, 2)	\n\t"
-		"addb %4, %%cl			\n\t" //2*xalpha += s_xinc&0xFF
+		"addw %4, %%cx			\n\t" //2*xalpha += s_xinc&0xFF
 		"adcl %3, %%ebx			\n\t" //xx+= s_xinc>>8 + carry
 
 
@@ -314,106 +387,96 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		" jb 1b				\n\t"
 
 
-		:: "r" (src), "m" (buf1), "m" (dstw), "m" (s_xinc>>8), "m" (s_xinc&0xFF)
+		:: "r" (src), "m" (buf1), "m" (dstw), "m" (s_xinc>>16), "m" (s_xinc&0xFFFF)
 		: "%eax", "%ebx", "%ecx", "%edi", "%esi"
 		);
+#ifdef HAVE_MMX2
+	} //if MMX2 cant be used
+#endif
 #else
       for(i=0;i<dstw;i++){
-	register unsigned int xx=xpos>>8;
-        register unsigned int xalpha=(xpos&0xFF)>>1;
+	register unsigned int xx=xpos>>16;
+        register unsigned int xalpha=(xpos&0xFFFF)>>9;
 	buf1[i]=(src[xx]*(xalpha^127)+src[xx+1]*xalpha);
 	xpos+=s_xinc;
       }
 #endif
+    }
       // *** horizontal scale U and V lines to temp buffer
-      if(!(y0&1)){
+    if(s_last_y1pos!=y1){
         unsigned char *src1=srcptr[1]+(y1-y/2)*stride[1];
         unsigned char *src2=srcptr[2]+(y1-y/2)*stride[2];
-        xpos=0;
-        // this loop should be rewritten in MMX assembly!!!!
+        int xpos=0;
+	s_last_y1pos= y1;
+#ifdef ARCH_X86
 #ifdef HAVE_MMX2
-	asm volatile(
+	if(canMMX2BeUsed)
+	{
+		asm volatile(
 		"pxor %%mm7, %%mm7		\n\t"
 		"pxor %%mm2, %%mm2		\n\t" // 2*xalpha
-		"movd %5, %%mm6			\n\t" // s_xinc&0xFF
+		"movd %5, %%mm6			\n\t" // s_xinc&0xFFFF
 		"punpcklwd %%mm6, %%mm6		\n\t"
 		"punpcklwd %%mm6, %%mm6		\n\t"
 		"movq %%mm6, %%mm2		\n\t"
 		"psllq $16, %%mm2		\n\t"
-		"paddb %%mm6, %%mm2		\n\t"
+		"paddw %%mm6, %%mm2		\n\t"
 		"psllq $16, %%mm2		\n\t"
-		"paddb %%mm6, %%mm2		\n\t"
-		"psllq $16, %%mm2		\n\t" //0,t,2t,3t		t=s_xinc&0xFF
+		"paddw %%mm6, %%mm2		\n\t"
+		"psllq $16, %%mm2		\n\t" //0,t,2t,3t		t=s_xinc&0xFFFF
 		"movq %%mm2, temp0		\n\t"
-		"movd %4, %%mm6			\n\t" //(s_xinc*4)&0xFF
+		"movd %4, %%mm6			\n\t" //(s_xinc*4)&0xFFFF
 		"punpcklwd %%mm6, %%mm6		\n\t"
 		"punpcklwd %%mm6, %%mm6		\n\t"
 		"xorl %%eax, %%eax		\n\t" // i
-		"xorl %%ebx, %%ebx		\n\t" // xx
 		"movl %0, %%esi			\n\t" // src
 		"movl %1, %%edi			\n\t" // buf1
-		"movl %3, %%edx			\n\t" // (s_xinc*4)>>8
+		"movl %3, %%edx			\n\t" // (s_xinc*4)>>16
 		"xorl %%ecx, %%ecx		\n\t"
-		"movb %4, %%ch			\n\t" // (s_xinc*4)&0xFF
+		"xorl %%ebx, %%ebx		\n\t"
+		"movw %4, %%bx			\n\t" // (s_xinc*4)&0xFFFF
+
 //	"int $3\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
+#define FUNNYUVCODE \
+		"call funnyUVCode		\n\t"\
+		"movq temp0, %%mm2		\n\t"\
+		"xorl %%ecx, %%ecx		\n\t"
+
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+
+
 
 		"xorl %%eax, %%eax		\n\t" // i
-		"xorl %%ebx, %%ebx		\n\t" // xx
 		"movl %6, %%esi			\n\t" // src
 		"movl %1, %%edi			\n\t" // buf1
 		"addl $4096, %%edi		\n\t"
 
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-		"movq temp0, %%mm2		\n\t"
-		"xorb %%cl, %%cl		\n\t"
-		"call funnyUVCode			\n\t"
-
-		:: "m" (src1), "m" (uvbuf1), "m" (dstw), "m" ((s_xinc2*4)>>8),
-		  "m" ((s_xinc2*4)&0xFF), "m" (s_xinc2&0xFF), "m" (src2)
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+FUNNYUVCODE
+
+		:: "m" (src1), "m" (uvbuf1), "m" (dstw), "m" ((s_xinc2*4)>>16),
+		  "m" ((s_xinc2*4)&0xFFFF), "m" (s_xinc2&0xFFFF), "m" (src2)
 		: "%eax", "%ebx", "%ecx", "%edx", "%esi", "%edi"
 	);
-
-#elif defined (ARCH_X86)
+	}
+	else
+	{
+#endif
 	asm volatile(
 		"xorl %%eax, %%eax		\n\t" // i
 		"xorl %%ebx, %%ebx		\n\t" // xx
@@ -424,46 +487,48 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		"movzbl 1(%%esi, %%ebx), %%esi	\n\t" //src[xx+1]
 		"subl %%edi, %%esi		\n\t" //src[xx+1] - src[xx]
 		"imull %%ecx, %%esi		\n\t" //(src[xx+1] - src[xx])*2*xalpha
-		"shll $8, %%edi			\n\t"
+		"shll $16, %%edi		\n\t"
 		"addl %%edi, %%esi		\n\t" //src[xx+1]*2*xalpha + src[xx]*(1-2*xalpha)
 		"movl %1, %%edi			\n\t"
-		"shrl $1, %%esi			\n\t"
+		"shrl $9, %%esi			\n\t"
 		"movw %%si, (%%edi, %%eax, 2)	\n\t"
 
 		"movzbl  (%5, %%ebx), %%edi	\n\t" //src[xx]
 		"movzbl 1(%5, %%ebx), %%esi	\n\t" //src[xx+1]
 		"subl %%edi, %%esi		\n\t" //src[xx+1] - src[xx]
 		"imull %%ecx, %%esi		\n\t" //(src[xx+1] - src[xx])*2*xalpha
-		"shll $8, %%edi			\n\t"
+		"shll $16, %%edi		\n\t"
 		"addl %%edi, %%esi		\n\t" //src[xx+1]*2*xalpha + src[xx]*(1-2*xalpha)
 		"movl %1, %%edi			\n\t"
-		"shrl $1, %%esi			\n\t"
+		"shrl $9, %%esi			\n\t"
 		"movw %%si, 4096(%%edi, %%eax, 2)\n\t"
 
-		"addb %4, %%cl			\n\t" //2*xalpha += s_xinc&0xFF
+		"addw %4, %%cx			\n\t" //2*xalpha += s_xinc&0xFF
 		"adcl %3, %%ebx			\n\t" //xx+= s_xinc>>8 + carry
 		"addl $1, %%eax			\n\t"
 		"cmpl %2, %%eax			\n\t"
 		" jb 1b				\n\t"
 
 
-		:: "m" (src1), "m" (uvbuf1), "m" (dstw), "m" (s_xinc2>>8), "m" (s_xinc2&0xFF),
+		:: "m" (src1), "m" (uvbuf1), "m" (dstw), "m" (s_xinc2>>16), "m" (s_xinc2&0xFFFF),
 		"r" (src2)
 		: "%eax", "%ebx", "%ecx", "%edi", "%esi"
 		);
+#ifdef HAVE_MMX2
+	} //if MMX2 cant be used
+#endif
 #else
-        for(i=0;i<dstw;i++){
-	  register unsigned int xx=xpos>>8;
-          register unsigned int xalpha=(xpos&0xFF)>>1;
+      for(i=0;i<dstw;i++){
+	  register unsigned int xx=xpos>>16;
+          register unsigned int xalpha=(xpos&0xFFFF)>>9;
 	  uvbuf1[i]=(src1[xx]*(xalpha^127)+src1[xx+1]*xalpha);
 	  uvbuf1[i+2048]=(src2[xx]*(xalpha^127)+src2[xx+1]*xalpha);
 	  xpos+=s_xinc2;
-        }
-#endif
       }
-      if(!y0) continue;
+#endif
     }
 
+
     // Note1: this code can be resticted to n*8 (or n*16) width lines to simplify optimization...
     // Re: Note1: ok n*4 for now
     // Note2: instead of using lookup tabs, mmx version could do the multiply...
@@ -489,47 +554,47 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		"1:				\n\t"\
 		"movq (%0, %%eax, 2), %%mm0	\n\t" /*buf0[eax]*/\
 		"movq (%1, %%eax, 2), %%mm1	\n\t" /*buf1[eax]*/\
-		"psubw %%mm1, %%mm0		\n\t" /* buf0[eax] - buf1[eax]*/\
-		"pmulhw %%mm6, %%mm0		\n\t" /* (buf0[eax] - buf1[eax])yalpha1>>16*/\
-		"psraw $7, %%mm1		\n\t" /* buf0[eax] - buf1[eax] >>7*/\
-		"paddw %%mm0, %%mm1		\n\t" /* buf0[eax]yalpha1 + buf1[eax](1-yalpha1) >>16*/\
-		"psubw w10, %%mm1		\n\t" /* Y-16*/\
-		"psllw $3, %%mm1		\n\t" /* (y-16)*8*/\
-		"pmulhw yCoeff, %%mm1		\n\t"\
-\
 		"movq (%2, %%eax,2), %%mm2	\n\t" /* uvbuf0[eax]*/\
 		"movq (%3, %%eax,2), %%mm3	\n\t" /* uvbuf1[eax]*/\
+		"psubw %%mm1, %%mm0		\n\t" /* buf0[eax] - buf1[eax]*/\
 		"psubw %%mm3, %%mm2		\n\t" /* uvbuf0[eax] - uvbuf1[eax]*/\
+		"pmulhw %%mm6, %%mm0		\n\t" /* (buf0[eax] - buf1[eax])yalpha1>>16*/\
 		"pmulhw %%mm5, %%mm2		\n\t" /* (uvbuf0[eax] - uvbuf1[eax])uvalpha1>>16*/\
+		"psraw $7, %%mm1		\n\t" /* buf0[eax] - buf1[eax] >>7*/\
+		"movq 4096(%2, %%eax,2), %%mm4	\n\t" /* uvbuf0[eax+2048]*/\
 		"psraw $7, %%mm3		\n\t" /* uvbuf0[eax] - uvbuf1[eax] >>7*/\
+		"paddw %%mm0, %%mm1		\n\t" /* buf0[eax]yalpha1 + buf1[eax](1-yalpha1) >>16*/\
+		"movq 4096(%3, %%eax,2), %%mm0	\n\t" /* uvbuf1[eax+2048]*/\
 		"paddw %%mm2, %%mm3		\n\t" /* uvbuf0[eax]uvalpha1 - uvbuf1[eax](1-uvalpha1)*/\
+		"psubw %%mm0, %%mm4		\n\t" /* uvbuf0[eax+2048] - uvbuf1[eax+2048]*/\
+		"psubw w10, %%mm1		\n\t" /* Y-16*/\
 		"psubw w80, %%mm3		\n\t" /* (U-128)*/\
+		"psllw $3, %%mm1		\n\t" /* (y-16)*8*/\
 		"psllw $3, %%mm3		\n\t" /*(U-128)8*/\
+		"pmulhw yCoeff, %%mm1		\n\t"\
+\
 \
-		"movq 4096(%2, %%eax,2), %%mm4	\n\t" /* uvbuf0[eax+2048]*/\
-		"movq 4096(%3, %%eax,2), %%mm0	\n\t" /* uvbuf1[eax+2048]*/\
-		"psubw %%mm0, %%mm4		\n\t" /* uvbuf0[eax+2048] - uvbuf1[eax+2048]*/\
 		"pmulhw %%mm5, %%mm4		\n\t" /* (uvbuf0[eax+2048] - uvbuf1[eax+2048])uvalpha1>>16*/\
+		"movq %%mm3, %%mm2		\n\t" /* (U-128)8*/\
+		"pmulhw ubCoeff, %%mm3		\n\t"\
 		"psraw $7, %%mm0		\n\t" /* uvbuf0[eax+2048] - uvbuf1[eax+2048] >>7*/\
+		"pmulhw ugCoeff, %%mm2		\n\t"\
 		"paddw %%mm4, %%mm0		\n\t" /* uvbuf0[eax+2048]uvalpha1 - uvbuf1[eax+2048](1-uvalpha1)*/\
 		"psubw w80, %%mm0		\n\t" /* (V-128)*/\
 		"psllw $3, %%mm0		\n\t" /* (V-128)8*/\
 \
-		"movq %%mm3, %%mm2		\n\t" /* (U-128)8*/\
-		"pmulhw ubCoeff, %%mm3		\n\t"\
-		"paddw %%mm1, %%mm3		\n\t" /* B*/\
 \
 		"movq %%mm0, %%mm4		\n\t" /* (V-128)8*/\
 		"pmulhw vrCoeff, %%mm0		\n\t"\
+		"pmulhw vgCoeff, %%mm4		\n\t"\
+		"paddw %%mm1, %%mm3		\n\t" /* B*/\
 		"paddw %%mm1, %%mm0		\n\t" /* R*/\
+		"packuswb %%mm3, %%mm3		\n\t"\
 \
-		"pmulhw ugCoeff, %%mm2		\n\t"\
-		"pmulhw vgCoeff, %%mm4		\n\t"\
+		"packuswb %%mm0, %%mm0		\n\t"\
 		"paddw %%mm4, %%mm2		\n\t"\
 		"paddw %%mm2, %%mm1		\n\t" /* G*/\
 \
-		"packuswb %%mm3, %%mm3		\n\t"\
-		"packuswb %%mm0, %%mm0		\n\t"\
 		"packuswb %%mm1, %%mm1		\n\t"
 
 YSCALEYUV2RGB
@@ -610,9 +675,11 @@ YSCALEYUV2RGB
 		asm volatile(
 
 YSCALEYUV2RGB
+#ifdef DITHER16BPP
 		"paddusb g16Dither, %%mm1	\n\t"
 		"paddusb b16Dither, %%mm0	\n\t"
 		"paddusb b16Dither, %%mm3	\n\t"
+#endif
 		"punpcklbw %%mm7, %%mm1		\n\t" // 0G0G0G0G
 		"punpcklbw %%mm7, %%mm3		\n\t" // 0B0B0B0B
 		"punpcklbw %%mm7, %%mm0		\n\t" // 0R0R0R0R
@@ -699,8 +766,6 @@ YSCALEYUV2RGB
 #elif defined (HAVE_MMX)
 	asm volatile("emms");
 #endif
-
-
 }
 
 
diff --git a/postproc/swscale_template.c b/postproc/swscale_template.c
index b02fe41152..049099abcb 100644
--- a/postproc/swscale_template.c
+++ b/postproc/swscale_template.c
@@ -1,28 +1,29 @@
 
 // Software scaling and colorspace conversion routines for MPlayer
 
+// Orginal C implementation by ?
+// current version mostly by Michael Niedermayer (michaelni@gmx.at)
+
 #include <inttypes.h>
 #include "../config.h"
 
-#undef HAVE_MMX2 //code is buggy
+//#undef HAVE_MMX2
 //#undef HAVE_MMX
+//#undef ARCH_X86
+#define DITHER16BPP
+#define ALT_ERROR
 
 #define RET 0xC3 //near return opcode
+/*
+NOTES
 
-// temporary storage for 4 yuv lines:
-// 16bit for now (mmx likes it more compact)
-static uint16_t pix_buf_y[4][2048];
-static uint16_t pix_buf_uv[2][2048*2];
+known BUGS with known cause (no bugreports please!)
+line at the right (c,asm and mmx2)
+code reads 1 sample too much (might cause a sig11)
 
-// clipping helper table for C implementations:
-static unsigned char clip_table[768];
-
-// yuv->rgb conversion tables:
-static    int yuvtab_2568[256];
-static    int yuvtab_3343[256];
-static    int yuvtab_0c92[256];
-static    int yuvtab_1a1e[256];
-static    int yuvtab_40cf[256];
+TODO
+check alignment off everything
+*/
 
 static uint64_t yCoeff=    0x2568256825682568LL;
 static uint64_t ubCoeff=   0x3343334333433343LL;
@@ -46,11 +47,27 @@ static uint64_t g16Mask=   0x07E007E007E007E0LL;
 static uint64_t r16Mask=   0xF800F800F800F800LL;
 static uint64_t temp0;
 
+
+// temporary storage for 4 yuv lines:
+// 16bit for now (mmx likes it more compact)
+static uint16_t pix_buf_y[4][2048];
+static uint16_t pix_buf_uv[2][2048*2];
+
+// clipping helper table for C implementations:
+static unsigned char clip_table[768];
+
+// yuv->rgb conversion tables:
+static    int yuvtab_2568[256];
+static    int yuvtab_3343[256];
+static    int yuvtab_0c92[256];
+static    int yuvtab_1a1e[256];
+static    int yuvtab_40cf[256];
+
+
 static uint8_t funnyYCode[10000];
 static uint8_t funnyUVCode[10000];
 
 
-
 // *** bilinear scaling and yuv->rgb conversion of yv12 slices:
 // *** Note: it's called multiple times while decoding a frame, first time y==0
 // *** Designed to upscale, but may work for downscale too.
@@ -64,27 +81,43 @@ void SwScale_YV12slice_brg24(unsigned char* srcptr[],int stride[], int y, int h,
 //static int s_yinc=(vo_dga_src_height<<16)/vo_dga_vp_height;
 //static int s_xinc=(vo_dga_src_width<<8)/vo_dga_vp_width;
 
-unsigned int s_xinc2=s_xinc>>1;
+unsigned int s_xinc2;
 
-static int s_srcypos;
+static int s_srcypos; // points to the dst Pixels center in the source (0 is the center of pixel 0,0 in src)
 static int s_ypos;
+
+// last horzontally interpolated lines, used to avoid unnecessary calculations
 static int s_last_ypos;
+static int s_last_y1pos;
+
 static int static_dstw;
 
 #ifdef HAVE_MMX2
+// used to detect a horizontal size change
 static int old_dstw= -1;
 static int old_s_xinc= -1;
+
+// difference between the requested xinc and the required one for the mmx2 routine
+static int s_xinc_diff=0;
+static int s_xinc2_diff=0;
 #endif
+int canMMX2BeUsed;
 
-s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each other
+// we need that precission at least for the mmx2 code
+s_xinc*= 256;
+s_xinc2=s_xinc>>1;
+canMMX2BeUsed= (s_xinc <= 0x10000 && (dstw&31)==0) ? 1 : 0;
 
   if(y==0){
-      s_srcypos=-2*s_yinc;
-      s_ypos=-2;
-      s_last_ypos=-2;
+      s_srcypos= s_yinc/2 - 0x8000;
+      s_ypos=0;
+
+      // force calculation of the horizontal interpolation of the first line
+      s_last_ypos=-99;
+      s_last_y1pos=-99;
 #ifdef HAVE_MMX2
 // cant downscale !!!
-	if(old_s_xinc != s_xinc || old_dstw!=dstw)
+	if((old_s_xinc != s_xinc || old_dstw!=dstw) && canMMX2BeUsed)
 	{
 		uint8_t *fragment;
 		int imm8OfPShufW1;
@@ -102,32 +135,30 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 
 		//code fragment
 
-//		fragmentLength=0;
-//		printf("%d, %d\n", fragmentLength,imm8OfPShufW1);
-
 		asm volatile(
 			"jmp 9f				\n\t"
 		// Begin
 			"0:				\n\t"
-			"movq (%%esi, %%ebx), %%mm0	\n\t" //FIXME Alignment
+			"movq (%%esi), %%mm0		\n\t" //FIXME Alignment
 			"movq %%mm0, %%mm1		\n\t"
 			"psrlq $8, %%mm0		\n\t"
 			"punpcklbw %%mm7, %%mm1	\n\t"
+			"movq %%mm2, %%mm3		\n\t"
 			"punpcklbw %%mm7, %%mm0	\n\t"
+			"addw %%bx, %%cx		\n\t" //2*xalpha += (4*s_xinc)&0xFFFF
 			"pshufw $0xFF, %%mm1, %%mm1	\n\t"
 			"1:				\n\t"
+			"adcl %%edx, %%esi		\n\t" //xx+= (4*s_xinc)>>16 + carry
 			"pshufw $0xFF, %%mm0, %%mm0	\n\t"
 			"2:				\n\t"
+			"psrlw $9, %%mm3		\n\t"
 			"psubw %%mm1, %%mm0		\n\t"
-			"psraw $1, %%mm0		\n\t"
-			"pmullw %%mm2, %%mm0		\n\t"
+			"pmullw %%mm3, %%mm0		\n\t"
+			"paddw %%mm6, %%mm2		\n\t" // 2*alpha += xpos&0xFFFF
 			"psllw $7, %%mm1		\n\t"
 			"paddw %%mm1, %%mm0		\n\t"
-			"movq %%mm0, (%%edi, %%eax)	\n\t"
-			"paddb %%mm6, %%mm2		\n\t" // 2*alpha += xpos&0xFF
 
-			"addb %%ch, %%cl		\n\t" //2*xalpha += (4*s_xinc)&0xFF
-			"adcl %%edx, %%ebx		\n\t" //xx+= (4*s_xinc)>>8 + carry
+			"movq %%mm0, (%%edi, %%eax)	\n\t"
 
 			"addl $8, %%eax			\n\t"
 		// End
@@ -147,17 +178,28 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		);
 
 		xpos= xx=xalpha= 0;
-		//FIXME choose size and or xinc so that they fit exactly
+
+		/* choose xinc so that all 8 parts fit exactly
+		   Note: we cannot use just 1 part because it would not fit in the code cache */
+		s_xinc2_diff= -((((s_xinc2*(dstw/8))&0xFFFF))/(dstw/8))+10;
+//		s_xinc_diff= -((((s_xinc*(dstw/8))&0xFFFF))/(dstw/8));
+#ifdef ALT_ERROR
+		s_xinc2_diff+= ((0x10000/(dstw/8)));
+#endif
+		s_xinc_diff= s_xinc2_diff*2;
+
+		s_xinc2+= s_xinc2_diff;
+		s_xinc+= s_xinc_diff;
 		for(i=0; i<dstw/8; i++)
 		{
-			int xx=xpos>>8;
+			int xx=xpos>>16;
 
 			if((i&3) == 0)
 			{
 				int a=0;
-				int b=((xpos+s_xinc)>>8) - xx;
-				int c=((xpos+s_xinc*2)>>8) - xx;
-				int d=((xpos+s_xinc*3)>>8) - xx;
+				int b=((xpos+s_xinc)>>16) - xx;
+				int c=((xpos+s_xinc*2)>>16) - xx;
+				int d=((xpos+s_xinc*3)>>16) - xx;
 
 				memcpy(funnyYCode + fragmentLength*i/4, fragment, fragmentLength);
 
@@ -174,14 +216,14 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 		//FIXME choose size and or xinc so that they fit exactly
 		for(i=0; i<dstw/8; i++)
 		{
-			int xx=xpos>>8;
+			int xx=xpos>>16;
 
 			if((i&3) == 0)
 			{
 				int a=0;
-				int b=((xpos+s_xinc2)>>8) - xx;
-				int c=((xpos+s_xinc2*2)>>8) - xx;
-				int d=((xpos+s_xinc2*3)>>8) - xx;
+				int b=((xpos+s_xinc2)>>16) - xx;
+				int c=((xpos+s_xinc2*2)>>16) - xx;
+				int d=((xpos+s_xinc2*3)>>16) - xx;
 
 				memcpy(funnyUVCode + fragmentLength*i/4, fragment, fragmentLength);
 
@@ -197,86 +239,117 @@ s_xinc&= -2; //clear last bit or uv and y might be shifted relative to each othe
 
 
 	}
-#endif
+
+	if(canMMX2BeUsed)
+	{
+		s_xinc+= s_xinc_diff;
+		s_xinc2+= s_xinc2_diff;
+	}
+#endif // HAVE_MMX2
   } // reset counters
 
   while(1){
     unsigned char *dest=dstptr+dststride*s_ypos;
-    int y0=2+(s_srcypos>>16);
-    int y1=1+(s_srcypos>>17);
+    int y0=(s_srcypos + 0xFFFF)>>16;  // first luminance source line number below the dst line
+	// points to the dst Pixels center in the source (0 is the center of pixel 0,0 in src)
+    int srcuvpos= s_srcypos + s_yinc/2 - 0x8000;
+    int y1=(srcuvpos + 0x1FFFF)>>17; // first chrominance source line number below the dst line
     int yalpha=(s_srcypos&0xFFFF)>>7;
     int yalpha1=yalpha^511;
-    int uvalpha=((s_srcypos>>1)&0xFFFF)>>7;
+    int uvalpha=(srcuvpos&0x1FFFF)>>8;
     int uvalpha1=uvalpha^511;
-    uint16_t *buf0=pix_buf_y[y0&3];
-    uint16_t *buf1=pix_buf_y[((y0+1)&3)];
-    uint16_t *uvbuf0=pix_buf_uv[y1&1];
-    uint16_t *uvbuf1=pix_buf_uv[(y1&1)^1];
+    uint16_t *buf0=pix_buf_y[y0&1];		// top line of the interpolated slice
+    uint16_t *buf1=pix_buf_y[((y0+1)&1)];	// bottom line of the interpolated slice
+    uint16_t *uvbuf0=pix_buf_uv[y1&1];		// top line of the interpolated slice
+    uint16_t *uvbuf1=pix_buf_uv[(y1+1)&1];	// bottom line of the interpolated slice
     int i;
 
-    if(y0>=y+h) break;
+    // if this is before the first line than use only the first src line
+    if(y0==0) buf0= buf1;
+    if(y1==0) uvbuf0= uvbuf1; // yes we do have to check this, its not the same as y0==0
+
+    if(y0>=y+h) break; // FIXME wrong, skips last lines, but they are dupliactes anyway
+
+    // if this is after the last line than use only the last src line
+    if(y0>=y+h)
+    {
+	buf1= buf0;
+	s_last_ypos=y0;
+    }
+    if(y1>=(y+h)/2)
+    {
+	uvbuf1= uvbuf0;
+	s_last_y1pos=y1;
+    }
+