Clean up VAD example and write to output file

examples/vad.rs

@@ -1,5 +1,6 @@
-use hound::SampleFormat;
+use hound::{SampleFormat, WavSpec, WavWriter};
 use std::io::Read;
+use std::time::Instant;
 use whisper_rs::{WhisperVadContext, WhisperVadContextParams, WhisperVadParams, WhisperVadSegment};
 
 fn main() {
@@ -9,14 +10,15 @@ fn main() {
     let wav_path = std::env::args()
         .nth(2)
         .expect("Please specify path to WAV file as argument 2");
+    let dest_path = std::env::args()
+        .nth(3)
+        .expect("Please specify output path as argument 3");
 
     let wav_reader = hound::WavReader::open(wav_path).expect("failed to open wav file");
-    assert_eq!(
-        wav_reader.spec().sample_rate,
-        16000,
-        "expected 16kHz sample rate"
-    );
-    assert_eq!(wav_reader.spec().channels, 1, "expected mono audio");
+    let input_sample_rate = wav_reader.spec().sample_rate;
+    let input_channels = wav_reader.spec().channels;
+    assert_eq!(input_sample_rate, 16000, "expected 16kHz sample rate");
+    assert_eq!(input_channels, 1, "expected mono audio");
 
     let samples = decode_to_float(wav_reader);
 
@@ -31,18 +33,39 @@ fn main() {
         WhisperVadContext::new(&model_path, vad_ctx_params).expect("failed to load model");
 
     let vad_params = WhisperVadParams::new();
+    let st = Instant::now();
     let result = vad_ctx
         .segments_from_samples(vad_params, &samples)
         .expect("failed to run VAD");
+    let et = Instant::now();
+    let dt = et.duration_since(st);
+    println!("took {:?} to run the VAD model", dt);
 
+    let mut output = WavWriter::create(
+        dest_path,
+        WavSpec {
+            channels: input_channels,
+            sample_rate: 16000,
+            bits_per_sample: 32,
+            sample_format: SampleFormat::Float,
+        },
+    )
+    .expect("failed to open output file");
     for WhisperVadSegment { start, end } in result {
-        println!(
-            "detected speech between {}s and {}s",
-            // each segment is in centiseconds so must be modified
-            start / 100.0,
-            end / 100.0
-        );
+        // convert from centiseconds to seconds
+        let start_ts = start / 100.0;
+        let end_ts = end / 100.0;
+        println!("detected speech between {}s and {}s", start_ts, end_ts);
+
+        let start_sample_idx = (start_ts * input_sample_rate as f32) as usize;
+        let end_sample_idx = (end_ts * input_sample_rate as f32) as usize;
+        for sample in &samples[start_sample_idx..end_sample_idx] {
+            output
+                .write_sample(*sample)
+                .expect("failed to write sample");
+        }
     }
+    output.finalize().expect("failed to finalize dest file");
 }
 
 fn decode_to_float<T: Read>(rdr: hound::WavReader<T>) -> Vec<f32> {