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#[derive(Default)]
pub struct RateControl {
bitrate: u32,
br_pool: u32,
f_pos: u32,
fracs: u32,
key_int: u32,
tb_num: u32,
tb_den: u32,
quality: Option<u8>,
}
impl RateControl {
pub fn new() -> Self { Self{ key_int: 10, ..Default::default() } }
pub fn set_quality(&mut self, quality: u8) {
if quality > 0 {
self.quality = Some((quality - 1).min(15));
} else {
self.quality = None;
}
}
pub fn set_bitrate(&mut self, br: u32, tb_num: u32, tb_den: u32) {
if tb_num > 0 && tb_den > 0 {
self.bitrate = br / 8;
self.tb_num = tb_num;
self.tb_den = tb_den;
} else {
self.bitrate = 0;
self.tb_num = 0;
self.tb_den = 0;
}
self.quality = Some(0);
self.reset();
}
pub fn set_key_int(&mut self, key_int: u32) {
self.key_int = key_int;
self.reset();
}
pub fn reset(&mut self) {
self.br_pool = self.bitrate;
self.f_pos = 0;
self.fracs = self.tb_den;
}
pub fn get_key_int(&self) -> u32 { self.key_int }
pub fn get_quant(&self, frameno: u32) -> (bool, Option<u8>) {
let is_intra = self.key_int == 0 || (frameno % self.key_int) == 0;
(is_intra, self.quality)
}
pub fn advance(&mut self, size: u32) {
if self.bitrate != 0 {
let expected = self.get_expected_size();
let cur_quant = self.quality.unwrap_or(0);
if (size > expected + expected / 10) && (cur_quant < 7) {
self.quality = Some(cur_quant + 1);
} else if (size < expected - expected / 10) && (cur_quant > 0) {
self.quality = Some(cur_quant - 1);
}
self.f_pos += self.tb_num;
while self.f_pos >= self.tb_den {
self.f_pos -= self.tb_den;
self.br_pool += self.bitrate;
self.fracs += self.tb_den;
}
self.fracs -= self.tb_num;
self.br_pool = self.br_pool.saturating_sub(size).min(self.bitrate * 3);
}
}
pub fn get_expected_size(&self) -> u32 {
if self.bitrate != 0 {
self.br_pool * self.tb_num / self.fracs
} else {
0
}
}
}
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