adds basic channel volume test not using queue

Author: dvdsk

Cargo.lock

@@ -56,6 +56,7 @@ rstest_reuse = "0.6.0"
 approx = "0.5.1"
 dasp_sample = "0.11.0"
 divan = "0.1.14"
+itertools = "0.14"
 
 [[bench]]
 name = "effects"

Cargo.toml

@@ -111,6 +111,7 @@ where
         // This function is non-trivial because the boundary between two
         // sounds in the queue should be a span boundary as well. Further more
         // we can *only* return Some(0) if the queue should stop playing.
+        //
         // This function can be called at any time though its normally only
         // called at the end of the span to get how long the next span will be.
         //
@@ -123,30 +124,6 @@ where
         // scenario. To handle this situation we force a span to have a
         // maximum number of samples with a constant. If the source ends before
         // that point we need to start silence for the remainder of the forced span.
-        //
-        // There are a lot of cases here:
-        // - not filling silence, current span is done
-        //     move to next
-        // - not filling silence, known span length.
-        //     report span length from current
-        // - not filling silence, unknown span length have lower bound.
-        //     report lower bound
-        // - not filling silence, unknown span length, no lower bound.
-        //     report fixed number of frames, if its too long we will get
-        //     silence for that length
-        // - filling silence, we have a next, however span is not finished,
-        //   next is same channel count and sample rate.
-        //     move to next,
-        // - filling silence, we have a next, however span is not finished,
-        //   next is diff channel count or sample rate.
-        //     play silence for rest of span
-        // - filling silence, we have a next, span is done
-        //     move to next
-        // - filling silence, no next, however span is not finished.
-        //     return samples left in span
-        // - filling silence, no next, span is done.
-        //     new silence span with fixed length, match previous sample_rate
-        //     and channel count.
 
         if let Some(len) = self.current.current_span_len() {
             // correct len for buffered sample

src/queue.rs

@@ -0,0 +1,31 @@
+use std::fs;
+use std::io::BufReader;
+
+use itertools::Itertools;
+
+use rodio::source::ChannelVolume;
+use rodio::{Decoder, Source};
+
+#[test]
+fn tomato() {
+    let file = fs::File::open("assets/music.mp3").unwrap();
+    let decoder = Decoder::new(BufReader::new(file)).unwrap();
+    assert_eq!(decoder.channels(), 2);
+    let channel_volume = ChannelVolume::new(decoder, vec![1.0, 1.0, 0.0, 0.0, 0.0, 0.0]);
+    assert_eq!(channel_volume.channels(), 6);
+
+    assert_output_only_on_channel_1_and_2(channel_volume);
+}
+
+fn assert_output_only_on_channel_1_and_2(source: impl Source<Item = i16>) {
+    for (frame_number, mut frame) in source.chunks(6).into_iter().enumerate() {
+        let frame: [_; 6] = frame.next_array().expect(&format!(
+            "Source should contain whole frames, frame {frame_number} was partial"
+        ));
+        assert_eq!(
+            &frame[2..],
+            &[0, 0, 0, 0],
+            "frame number {frame_number} had nonzero volume on channels 3,4,5 & 6"
+        )
+    }
+}