Update model plumbing for Rust example

The v6.2 models broke the Rust example. Update the logic for driving
them to reflect what the reference Python code does.

Fixes: #745
Co-Authored-By: Claude <noreply@anthropic.com>

examples/rust-example/src/silero.rs

@@ -1,5 +1,5 @@
 use crate::utils;
-use ndarray::{s, Array, Array2, ArrayBase, ArrayD, Dim, IxDynImpl, OwnedRepr};
+use ndarray::{Array, Array1, Array2, ArrayBase, ArrayD, Dim, IxDynImpl, OwnedRepr};
 use std::path::Path;
 
 #[derive(Debug)]
@@ -7,6 +7,8 @@ pub struct Silero {
     session: ort::Session,
     sample_rate: ArrayBase<OwnedRepr<i64>, Dim<[usize; 1]>>,
     state: ArrayBase<OwnedRepr<f32>, Dim<IxDynImpl>>,
+    context: Array1<f32>,
+    context_size: usize,
 }
 
 impl Silero {
@@ -16,16 +18,22 @@ impl Silero {
     ) -> Result<Self, ort::Error> {
         let session = ort::Session::builder()?.commit_from_file(model_path)?;
         let state = ArrayD::<f32>::zeros([2, 1, 128].as_slice());
-        let sample_rate = Array::from_shape_vec([1], vec![sample_rate.into()]).unwrap();
+        let sample_rate_val: i64 = sample_rate.into();
+        let context_size = if sample_rate_val == 16000 { 64 } else { 32 };
+        let context = Array1::<f32>::zeros(context_size);
+        let sample_rate = Array::from_shape_vec([1], vec![sample_rate_val]).unwrap();
         Ok(Self {
             session,
             sample_rate,
             state,
+            context,
+            context_size,
         })
     }
 
     pub fn reset(&mut self) {
         self.state = ArrayD::<f32>::zeros([2, 1, 128].as_slice());
+        self.context = Array1::<f32>::zeros(self.context_size);
     }
 
     pub fn calc_level(&mut self, audio_frame: &[i16]) -> Result<f32, ort::Error> {
@@ -33,8 +41,14 @@ impl Silero {
             .iter()
             .map(|x| (*x as f32) / (i16::MAX as f32))
             .collect::<Vec<_>>();
-        let mut frame = Array2::<f32>::from_shape_vec([1, data.len()], data).unwrap();
-        frame = frame.slice(s![.., ..480]).to_owned();
+
+        // Concatenate context with input
+        let mut input_with_context = Vec::with_capacity(self.context_size + data.len());
+        input_with_context.extend_from_slice(self.context.as_slice().unwrap());
+        input_with_context.extend_from_slice(&data);
+
+        let frame = Array2::<f32>::from_shape_vec([1, input_with_context.len()], input_with_context).unwrap();
+
         let inps = ort::inputs![
             frame,
             std::mem::take(&mut self.state),
@@ -43,12 +57,20 @@ impl Silero {
         let res = self
             .session
             .run(ort::SessionInputs::ValueSlice::<3>(&inps))?;
+
         self.state = res["stateN"].try_extract_tensor().unwrap().to_owned();
-        Ok(*res["output"]
+
+        // Update context with last context_size samples from the input
+        if data.len() >= self.context_size {
+            self.context = Array1::from_vec(data[data.len() - self.context_size..].to_vec());
+        }
+
+        let prob = *res["output"]
             .try_extract_raw_tensor::<f32>()
             .unwrap()
             .1
             .first()
-            .unwrap())
+            .unwrap();
+        Ok(prob)
     }
 }

examples/rust-example/src/utils.rs

@@ -36,7 +36,7 @@ pub struct VadParams {
 impl Default for VadParams {
     fn default() -> Self {
         Self {
-            frame_size: 64,
+            frame_size: 32,  // 32ms for 512 samples at 16kHz
             threshold: 0.5,
             min_silence_duration_ms: 0,
             speech_pad_ms: 64,