Use TV range algorithm for bit-depth conversions

[x264] / filters / video / depth.c

diff --git a/filters/video/depth.c b/filters/video/depth.c
index 43b84db91ce378f143a76c3687c3032e079ab891..e01aaae4f46cdebbaedf2cb2cc92aec95764af41 100644 (file)
--- a/filters/video/depth.c
+++ b/filters/video/depth.c
@@ -65,12 +65,12 @@ static int csp_num_interleaved( int csp, int plane )
  * depth again is lossless. */
 #define DITHER_PLANE( pitch ) \
 static void dither_plane_##pitch( pixel *dst, int dst_stride, uint16_t *src, int src_stride, \
-                                        int width, int height, int16_t *errors ) \
+                                  int width, int height, int16_t *errors ) \
 { \
     const int lshift = 16-BIT_DEPTH; \
-    const int rshift = 2*BIT_DEPTH-16; \
+    const int rshift = 16-BIT_DEPTH+2; \
+    const int half = 1 << (16-BIT_DEPTH+1); \
     const int pixel_max = (1 << BIT_DEPTH)-1; \
-    const int half = 1 << (16-BIT_DEPTH); \
     memset( errors, 0, (width+1) * sizeof(int16_t) ); \
     for( int y = 0; y < height; y++, src += src_stride, dst += dst_stride ) \
     { \
@@ -78,8 +78,8 @@ static void dither_plane_##pitch( pixel *dst, int dst_stride, uint16_t *src, int
         for( int x = 0; x < width; x++ ) \
         { \
             err = err*2 + errors[x] + errors[x+1]; \
-            dst[x*pitch] = x264_clip3( (((src[x*pitch]+half)<<2)+err)*pixel_max >> 18, 0, pixel_max ); \
-            errors[x] = err = src[x*pitch] - (dst[x*pitch] << lshift) - (dst[x*pitch] >> rshift); \
+            dst[x*pitch] = x264_clip3( ((src[x*pitch]<<2)+err+half) >> rshift, 0, pixel_max ); \
+            errors[x] = err = src[x*pitch] - (dst[x*pitch] << lshift); \
         } \
     } \
 }
@@ -114,13 +114,8 @@ static void dither_image( cli_image_t *out, cli_image_t *img, int16_t *error_buf
 
 static void scale_image( cli_image_t *output, cli_image_t *img )
 {
-    /* this function mimics how swscale does upconversion. 8-bit is converted
-     * to 16-bit through left shifting the orginal value with 8 and then adding
-     * the original value to that. This effectively keeps the full color range
-     * while also being fast. for n-bit we basically do the same thing, but we
-     * discard the lower 16-n bits. */
     int csp_mask = img->csp & X264_CSP_MASK;
-    const int shift = 16-BIT_DEPTH;
+    const int shift = BIT_DEPTH - 8;
     for( int i = 0; i < img->planes; i++ )
     {
         uint8_t *src = img->plane[i];
@@ -131,7 +126,7 @@ static void scale_image( cli_image_t *output, cli_image_t *img )
         for( int j = 0; j < height; j++ )
         {
             for( int k = 0; k < width; k++ )
-                dst[k] = ((src[k] << 8) + src[k]) >> shift;
+                dst[k] = src[k] << shift;
 
             src += img->stride[i];
             dst += output->stride[i]/2;