///! Maximum step value for IMA ADPCM.
pub const IMA_MAX_STEP: u8 = 88;
+#[derive(Clone,Copy,Debug)]
///! Decoder for IMA ADPCM.
pub struct IMAState {
///! Current sample value.
self.step = istep.max(0).min(IMA_MAX_STEP as isize) as usize;
self.predictor as i16
}
+ ///! Computes an encoded nibble from an input sample.
+ pub fn compress_sample(&self, sample: i16) -> u8 {
+ let diff = i32::from(sample) - self.predictor;
+ let sign = if diff >= 0 { 0 } else { 8 };
+ let nib = (diff.abs() * 4 / IMA_STEP_TABLE[self.step]).min(7) as u8;
+ nib | sign
+ }
}
impl Default for IMAState {