vp6enc: split out future common parts to share them with VP7 encoder

[nihav.git] / nihav-duck / src / codecs / vpenc / models.rs

diff --git a/nihav-duck/src/codecs/vpenc/models.rs b/nihav-duck/src/codecs/vpenc/models.rs
new file mode 100644 (file)
index 0000000..0495c89
--- /dev/null
+++ b/nihav-duck/src/codecs/vpenc/models.rs
@@ -0,0 +1,75 @@
+#[derive(Clone,Copy,Default)]
+pub struct ProbCounter {
+    zeroes: u32,
+    total:  u32,
+}
+
+// bits to code zero probability multiplied by eight
+pub const PROB_BITS: [u8; 256] = [
+     0, 64, 56, 51, 48, 45, 43, 42,
+    40, 39, 37, 36, 35, 34, 34, 33,
+    32, 31, 31, 30, 29, 29, 28, 28,
+    27, 27, 26, 26, 26, 25, 25, 24,
+    24, 24, 23, 23, 23, 22, 22, 22,
+    21, 21, 21, 21, 20, 20, 20, 20,
+    19, 19, 19, 19, 18, 18, 18, 18,
+    18, 17, 17, 17, 17, 17, 16, 16,
+    16, 16, 16, 15, 15, 15, 15, 15,
+    15, 14, 14, 14, 14, 14, 14, 14,
+    13, 13, 13, 13, 13, 13, 13, 12,
+    12, 12, 12, 12, 12, 12, 12, 11,
+    11, 11, 11, 11, 11, 11, 11, 11,
+    10, 10, 10, 10, 10, 10, 10, 10,
+    10,  9,  9,  9,  9,  9,  9,  9,
+     9,  9,  9,  8,  8,  8,  8,  8,
+     8,  8,  8,  8,  8,  8,  7,  7,
+     7,  7,  7,  7,  7,  7,  7,  7,
+     7,  7,  6,  6,  6,  6,  6,  6,
+     6,  6,  6,  6,  6,  6,  6,  5,
+     5,  5,  5,  5,  5,  5,  5,  5,
+     5,  5,  5,  5,  5,  5,  4,  4,
+     4,  4,  4,  4,  4,  4,  4,  4,
+     4,  4,  4,  4,  4,  4,  3,  3,
+     3,  3,  3,  3,  3,  3,  3,  3,
+     3,  3,  3,  3,  3,  3,  3,  2,
+     2,  2,  2,  2,  2,  2,  2,  2,
+     2,  2,  2,  2,  2,  2,  2,  2,
+     2,  1,  1,  1,  1,  1,  1,  1,
+     1,  1,  1,  1,  1,  1,  1,  1,
+     1,  1,  1,  1,  1,  1,  0,  0,
+     0,  0,  0,  0,  0,  0,  0,  0
+];
+
+impl ProbCounter {
+    pub fn add(&mut self, b: bool) {
+        if !b {
+            self.zeroes += 1;
+        }
+        self.total += 1;
+    }
+    pub fn to_prob(self) -> u8 {
+        if self.total > 0 {
+            (((self.zeroes << 8) / self.total).min(254) & !1).max(1) as u8
+        } else {
+            128
+        }
+    }
+    pub fn to_prob_worthy(&self, old_prob: u8) -> u8 {
+        if self.total > 0 {
+            let new_prob = self.to_prob();
+            let new_bits = Self::est_bits(new_prob, self.zeroes, self.total);
+            let old_bits = Self::est_bits(old_prob, self.zeroes, self.total);
+
+            if new_bits + 7 < old_bits {
+                new_prob
+            } else {
+                old_prob
+            }
+        } else {
+            old_prob
+        }
+    }
+    fn est_bits(prob: u8, zeroes: u32, total: u32) -> u32 {
+        (u32::from(PROB_BITS[prob as usize]) * zeroes + u32::from(PROB_BITS[256 - (prob as usize)]) * (total - zeroes) + 7) >> 3
+    }
+}