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Merge pull request #8 from tomaka/optimize-channels-converter

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Optimize the channels counter converter
This commit is contained in:
tomaka 2015-09-11 12:50:59 +02:00
commit b088c15740
1 changed files with 24 additions and 26 deletions
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50
src/decoder/conversions.rs
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@ -153,7 +153,8 @@ pub struct ChannelsCountConverter<I> where I: Iterator {
input: I,
from: cpal::ChannelsCount,
to: cpal::ChannelsCount,
output_buffer: Vec<I::Item>,
sample_repeat: Option<I::Item>,
next_output_sample_pos: cpal::ChannelsCount,
}
impl<I> ChannelsCountConverter<I> where I: Iterator {
@ -174,7 +175,8 @@ impl<I> ChannelsCountConverter<I> where I: Iterator {
input: input,
from: from,
to: to,
output_buffer: Vec::with_capacity(to as usize),
sample_repeat: None,
next_output_sample_pos: 0,
}
}
}
@ -183,41 +185,37 @@ impl<I> Iterator for ChannelsCountConverter<I> where I: Iterator, I::Item: Clone
type Item = I::Item;
fn next(&mut self) -> Option<I::Item> {
if self.output_buffer.len() == 0 {
// copying common channels from input to output
for _ in (0 .. cmp::min(self.from, self.to)) {
self.output_buffer.push(match self.input.next() {
Some(i) => i,
None => return None
});
}
let result = if self.next_output_sample_pos == self.from - 1 {
let value = self.input.next();
self.sample_repeat = value.clone();
value
} else if self.next_output_sample_pos < self.from {
self.input.next()
} else {
self.sample_repeat.clone()
};
// adding extra output channels
// TODO: could be done better
if self.to > self.from {
for i in (0 .. self.to - self.from) {
let val = self.output_buffer[(i % self.from) as usize].clone();
self.output_buffer.push(val);
}
}
self.next_output_sample_pos += 1;
if self.next_output_sample_pos == self.to {
self.next_output_sample_pos -= self.to;
// discarding extra channels
if self.from > self.to {
for _ in (0 .. self.from - self.to) {
let _ = self.input.next();
for _ in (self.to .. self.from) {
self.input.next(); // discarding extra input
}
}
}
Some(self.output_buffer.remove(0))
result
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (min, max) = self.input.size_hint();
let min = (min / self.from as usize) * self.to as usize + self.output_buffer.len();
let max = max.map(|max| (max / self.from as usize) * self.to as usize + self.output_buffer.len());
let min = (min / self.from as usize) * self.to as usize + self.next_output_sample_pos as usize;
let max = max.map(|max| (max / self.from as usize) * self.to as usize + self.next_output_sample_pos as usize);
(min, max)
}
@ -367,11 +365,11 @@ mod test {
fn add_channels() {
let input = vec![1u16, 2, 1, 2];
let output = ChannelsCountConverter::new(input.into_iter(), 2, 3).collect::<Vec<_>>();
assert_eq!(output, [1, 2, 1, 1, 2, 1]);
assert_eq!(output, [1, 2, 2, 1, 2, 2]);
let input = vec![1u16, 2, 1, 2];
let output = ChannelsCountConverter::new(input.into_iter(), 2, 4).collect::<Vec<_>>();
assert_eq!(output, [1, 2, 1, 2, 1, 2, 1, 2]);
assert_eq!(output, [1, 2, 2, 2, 1, 2, 2, 2]);
}
/*