rosa 0.1.0

Audio feature extraction library matching librosa output
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

/// Zero-copy overlapping frames over a signal.
/// Each frame is a contiguous slice of the original data.
/// Equivalent to librosa's `util.frame()`.
pub struct FrameIter<'a> {
    data: &'a [f64],
    frame_length: usize,
    hop_length: usize,
    current: usize,
    n_frames: usize,
}

impl<'a> FrameIter<'a> {
    /// Create a new frame iterator.
    /// `n_frames = 1 + (data.len() - frame_length) / hop_length` if `data.len() >= frame_length`, else 0.
    pub fn new(data: &'a [f64], frame_length: usize, hop_length: usize) -> Self {
        let n_frames = if data.len() >= frame_length {
            1 + (data.len() - frame_length) / hop_length
        } else {
            0
        };
        Self {
            data,
            frame_length,
            hop_length,
            current: 0,
            n_frames,
        }
    }

    /// Number of frames.
    pub fn n_frames(&self) -> usize {
        self.n_frames
    }

    /// Random access to frame by index.
    pub fn frame(&self, i: usize) -> &[f64] {
        assert!(
            i < self.n_frames,
            "frame index {} out of bounds for {} frames",
            i,
            self.n_frames
        );
        let start = i * self.hop_length;
        &self.data[start..start + self.frame_length]
    }
}

impl<'a> Iterator for FrameIter<'a> {
    type Item = &'a [f64];

    fn next(&mut self) -> Option<Self::Item> {
        if self.current >= self.n_frames {
            return None;
        }
        let start = self.current * self.hop_length;
        self.current += 1;
        Some(&self.data[start..start + self.frame_length])
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let rem = self.n_frames - self.current;
        (rem, Some(rem))
    }
}

impl ExactSizeIterator for FrameIter<'_> {}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_basic_framing() {
        // 10 samples, frame_length=4, hop_length=2 → 4 frames
        let data: Vec<f64> = (0..10).map(|i| i as f64).collect();
        let iter = FrameIter::new(&data, 4, 2);
        assert_eq!(iter.n_frames(), 4);

        let frames: Vec<&[f64]> = iter.collect();
        assert_eq!(frames.len(), 4);
        assert_eq!(frames[0], &[0.0, 1.0, 2.0, 3.0]);
        assert_eq!(frames[1], &[2.0, 3.0, 4.0, 5.0]);
        assert_eq!(frames[2], &[4.0, 5.0, 6.0, 7.0]);
        assert_eq!(frames[3], &[6.0, 7.0, 8.0, 9.0]);
    }

    #[test]
    fn test_frame_equals_data_length() {
        let data = vec![1.0, 2.0, 3.0, 4.0];
        let iter = FrameIter::new(&data, 4, 1);
        assert_eq!(iter.n_frames(), 1);
        let frames: Vec<&[f64]> = iter.collect();
        assert_eq!(frames[0], &[1.0, 2.0, 3.0, 4.0]);
    }

    #[test]
    fn test_data_shorter_than_frame() {
        let data = vec![1.0, 2.0];
        let iter = FrameIter::new(&data, 4, 1);
        assert_eq!(iter.n_frames(), 0);
        assert_eq!(iter.count(), 0);
    }

    #[test]
    fn test_hop_length_one() {
        let data: Vec<f64> = (0..6).map(|i| i as f64).collect();
        let iter = FrameIter::new(&data, 3, 1);
        // 1 + (6-3)/1 = 4 frames
        assert_eq!(iter.n_frames(), 4);
    }

    #[test]
    fn test_iterator_count_matches_n_frames() {
        let data: Vec<f64> = (0..20).map(|i| i as f64).collect();
        let iter = FrameIter::new(&data, 5, 3);
        let n = iter.n_frames();
        assert_eq!(iter.count(), n);
    }

    #[test]
    fn test_random_access_matches_sequential() {
        let data: Vec<f64> = (0..15).map(|i| i as f64).collect();
        let iter = FrameIter::new(&data, 4, 2);
        let n = iter.n_frames();

        let sequential: Vec<Vec<f64>> = FrameIter::new(&data, 4, 2).map(|f| f.to_vec()).collect();

        for i in 0..n {
            let random = iter.frame(i);
            assert_eq!(random, sequential[i].as_slice());
        }
    }

    #[test]
    fn test_size_hint_exact() {
        let data: Vec<f64> = (0..10).map(|i| i as f64).collect();
        let mut iter = FrameIter::new(&data, 4, 2);
        assert_eq!(iter.len(), 4);
        iter.next();
        assert_eq!(iter.len(), 3);
        iter.next();
        assert_eq!(iter.len(), 2);
    }
}