Ticket #5259: yuyv_yuv420p_interlaced.patch

libs/libmythtv/NuppelVideoRecorder.cpp

@@ -1559 +1559 @@
 
                 uint8_t *src = buffers[frame];
 
-                // Round height to multiple of two.
-                unsigned height = (h / 2) * 2;
+                // Interlaced chroma subsampling: samples reside between
+                // scan lines and are linearly interpolated using the
+                // nearest lines from the same field.
 
-                // Treat lines in batches of two, first use color information, then don't
+                // Round height to multiple of four.
+                unsigned height = (h / 4) * 4;
+
                 unsigned line_size = w * 2;
 
-                for (unsigned line = 0; line < height; line += 2)
+                // Treat lines in batches of four
+                for (unsigned line = 0; line < height; line += 4)
                 {
                     uint8_t *src_endline = src + line_size;
+                    uint8_t *src2 = src + line_size * 2;
 
-                    // convert first line, use color information
+                    // luma from line 1 and chroma from lines 1 and 3
                     while (src < src_endline)
                     {
                         *y_plane++ = *src++;
-                        *cb_plane++ = *src++;
+                        src2++;
+                        *cb_plane++ = (*src++ * 3 + *src2++) / 4;
                         *y_plane++ = *src++;
-                        *cr_plane++ = *src++;
+                        src2++;
+                        *cr_plane++ = (*src++ * 3 + *src2++) / 4;
                     }
 
                     src_endline = src + line_size;
 
-                    // convert second line, don't use color information
+                    // luma from line 2 and chroma from lines 2 and 4
                     while (src < src_endline)
                     {
                         *y_plane++ = *src++;
+                        src2++;
+                        *cb_plane++ = (*src++ + *src2++ * 3) / 4;
+                        *y_plane++ = *src++;
+                        src2++;
+                        *cr_plane++ = (*src++ + *src2++ * 3) / 4;
+                    }
+
+                    src_endline = src + line_size * 2;
+
+                    // luma from line 3 and from line 4
+                    while (src < src_endline)
+                    {
+                        *y_plane++ = *src++;
                         src++;
                         *y_plane++ = *src++;
                         src++;