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BE bitstream, flip bit encoding

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This commit is contained in:
Dennis Ranke
2022-09-10 11:31:09 +02:00
parent 629c5fce7d
commit 36cb6d77b5
2 changed files with 13 additions and 13 deletions
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4
src/context_state.rs
View File

@@ -1,4 +1,4 @@
use crate::rans::{PROB_BITS, ONE_PROB}; use crate::rans::{ONE_PROB, PROB_BITS};
const INIT_PROB: u16 = 1 << (PROB_BITS - 1); const INIT_PROB: u16 = 1 << (PROB_BITS - 1);
const UPDATE_RATE: u32 = 4; const UPDATE_RATE: u32 = 4;
@@ -33,7 +33,7 @@ impl<'a> Context<'a> {
pub fn update(&mut self, bit: bool) { pub fn update(&mut self, bit: bool) {
let old = self.state.contexts[self.index]; let old = self.state.contexts[self.index];
self.state.contexts[self.index] = if bit { self.state.contexts[self.index] = if !bit {
old + ((ONE_PROB - old as u32 + UPDATE_ADD) >> UPDATE_RATE) as u8 old + ((ONE_PROB - old as u32 + UPDATE_ADD) >> UPDATE_RATE) as u8
} else { } else {
old - ((old as u32 + UPDATE_ADD) >> UPDATE_RATE) as u8 old - ((old as u32 + UPDATE_ADD) >> UPDATE_RATE) as u8

22
src/rans.rs
View File

@@ -38,15 +38,15 @@ impl RansCoder {
let mut state = 1 << l_bits; let mut state = 1 << l_bits;
let mut byte = 0u8; let mut byte = 0u8;
let mut bit = 8; let mut bit = 0;
let mut flush_state: Box<dyn FnMut(&mut u32)> = if self.use_bitstream { let mut flush_state: Box<dyn FnMut(&mut u32)> = if self.use_bitstream {
Box::new(|state: &mut u32| { Box::new(|state: &mut u32| {
bit -= 1;
byte |= ((*state & 1) as u8) << bit; byte |= ((*state & 1) as u8) << bit;
if bit == 0 { bit += 1;
if bit == 8 {
buffer.push(byte); buffer.push(byte);
byte = 0; byte = 0;
bit = 8; bit = 0;
} }
*state >>= 1; *state >>= 1;
}) })
@@ -61,7 +61,7 @@ impl RansCoder {
let max_state_factor: u32 = 1 << (l_bits + num_flush_bits - PROB_BITS); let max_state_factor: u32 = 1 << (l_bits + num_flush_bits - PROB_BITS);
for step in self.bits.into_iter().rev() { for step in self.bits.into_iter().rev() {
let prob = step as u32 & 32767; let prob = step as u32 & 32767;
let (start, prob) = if step & 32768 != 0 { let (start, prob) = if step & 32768 == 0 {
(0, prob) (0, prob)
} else { } else {
(prob, ONE_PROB - prob) (prob, ONE_PROB - prob)
@@ -118,7 +118,7 @@ impl CostCounter {
impl EntropyCoder for CostCounter { impl EntropyCoder for CostCounter {
fn encode_bit(&mut self, bit: bool, prob: u16) { fn encode_bit(&mut self, bit: bool, prob: u16) {
let prob = if bit { let prob = if !bit {
prob as u32 prob as u32
} else { } else {
ONE_PROB - prob as u32 ONE_PROB - prob as u32
@@ -163,8 +163,8 @@ impl<'a> RansDecoder<'a> {
self.data = &self.data[1..]; self.data = &self.data[1..];
self.bits_left = 8; self.bits_left = 8;
} }
self.state = (self.state << 1) | (self.byte & 1) as u32; self.state = (self.state << 1) | (self.byte >> 7) as u32;
self.byte >>= 1; self.byte <<= 1;
self.bits_left -= 1; self.bits_left -= 1;
} }
} else { } else {
@@ -174,12 +174,12 @@ impl<'a> RansDecoder<'a> {
} }
} }
let bit = (self.state & PROB_MASK) < prob; let bit = (self.state & PROB_MASK) >= prob;
let (start, prob) = if bit { let (start, prob) = if bit {
(0, prob)
} else {
(prob, ONE_PROB - prob) (prob, ONE_PROB - prob)
} else {
(0, prob)
}; };
self.state = prob * (self.state >> PROB_BITS) + (self.state & PROB_MASK) - start; self.state = prob * (self.state >> PROB_BITS) + (self.state & PROB_MASK) - start;