works

1 files changed, 16 insertions, 7 deletions

diff --git a/test2/src/encode.rs b/test2/src/encode.rs
index 8db88b0..7eb82e0 100644
--- a/test2/src/encode.rs
+++ b/test2/src/encode.rs
@@ -25,8 +25,8 @@ impl BitstreamFilter for Enc {
         };
 
         let mut out = Vec::new();
-        let mut oldblock = Vec::new();
-        let mut newblock = Vec::new();
+        let mut savblock = Vec::new();
+        let mut refblock = Vec::new();
 
         for by in 0..frame.res.y / BLOCK_SIZE {
             for bx in 0..frame.res.x / BLOCK_SIZE {
@@ -61,20 +61,29 @@ impl BitstreamFilter for Enc {
                     }
                 }
 
-                oldblock.clear();
-                frame.export_block(boff, &mut oldblock);
+                savblock.clear();
+                frame.export_block(boff, &mut savblock);
 
                 Frame::copy_block(&self.last, &mut frame, best_off, boff);
 
-                newblock.clear();
-                frame.export_block(boff, &mut newblock);
+                refblock.clear();
+                frame.export_block(boff, &mut refblock);
 
                 let reloff = best_off - boff;
                 out.push((reloff.x + 127) as u8);
                 out.push((reloff.y + 127) as u8);
 
                 for i in 0..(BLOCK_SIZE * BLOCK_SIZE + BLOCK_SIZE * BLOCK_SIZE / 2) {
-                    out.push(oldblock[i as usize] - newblock[i as usize])
+                    let mut d = savblock[i as usize] - refblock[i as usize];
+                    let neg = d > 127;
+                    if neg {
+                        d = (-(d as i8)) as u8;
+                    }
+                    d &= 0xff << (6 - d.leading_zeros()); // only keep 3 msb
+                    if neg {
+                        d = (-(d as i8)) as u8;
+                    }
+                    out.push(d)
                 }
 
                 frame.import_block_diff(