stft-rs 0.6.0

Simple, streaming-friendly, no_std compliant STFT implementation with mel spectrogram support
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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287

/// Utility functions for signal processing and multi-channel audio
use num_traits::Float;

#[cfg(not(feature = "std"))]
use alloc::{vec, vec::Vec};

#[cfg(feature = "std")]
use std::vec;

use crate::PadMode;

/// Apply padding to a signal.
/// Streaming applications should pad manually to match batch processing quality.
pub fn apply_padding<T: Float>(signal: &[T], pad_amount: usize, mode: PadMode) -> Vec<T> {
    let total_len = signal.len() + 2 * pad_amount;
    let mut padded = vec![T::zero(); total_len];

    padded[pad_amount..pad_amount + signal.len()].copy_from_slice(signal);

    match mode {
        PadMode::Reflect => {
            for i in 0..pad_amount {
                if i + 1 < signal.len() {
                    padded[pad_amount - 1 - i] = signal[i + 1];
                }
            }

            let n = signal.len();
            for i in 0..pad_amount {
                if n >= 2 && n - 2 >= i {
                    padded[pad_amount + n + i] = signal[n - 2 - i];
                }
            }
        }
        PadMode::Zero => {}
        PadMode::Edge => {
            if !signal.is_empty() {
                for i in 0..pad_amount {
                    padded[i] = signal[0];
                }
                for i in 0..pad_amount {
                    padded[pad_amount + signal.len() + i] = signal[signal.len() - 1];
                }
            }
        }
    }

    padded
}

// ============================================================================
// Multi-Channel Utilities
// ============================================================================

/// Deinterleave multi-channel audio data.
///
/// Converts interleaved format (e.g., `[L,R,L,R,L,R,...]` for stereo)
/// into separate channels (`vec![vec![L,L,L,...], vec![R,R,R,...]]`).
///
/// # Arguments
///
/// * `data` - Interleaved audio data
/// * `num_channels` - Number of channels
///
/// # Panics
///
/// Panics if `num_channels` is 0 or if `data.len()` is not divisible by `num_channels`.
///
/// # Example
///
/// ```
/// use stft_rs::deinterleave;
///
/// let interleaved = vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]; // L,R,L,R,L,R
/// let channels = deinterleave(&interleaved, 2);
///
/// assert_eq!(channels[0], vec![1.0, 3.0, 5.0]); // Left
/// assert_eq!(channels[1], vec![2.0, 4.0, 6.0]); // Right
/// ```
pub fn deinterleave<T: Float>(data: &[T], num_channels: usize) -> Vec<Vec<T>> {
    assert!(num_channels > 0, "num_channels must be greater than 0");
    assert_eq!(
        data.len() % num_channels,
        0,
        "data length ({}) must be divisible by num_channels ({})",
        data.len(),
        num_channels
    );

    if data.is_empty() {
        return vec![Vec::new(); num_channels];
    }

    let samples_per_channel = data.len() / num_channels;
    let mut channels = vec![Vec::with_capacity(samples_per_channel); num_channels];

    for (i, &sample) in data.iter().enumerate() {
        channels[i % num_channels].push(sample);
    }

    channels
}

/// Deinterleave multi-channel audio into a pre-allocated buffer (zero-allocation).
///
/// Converts interleaved format into separate channels without allocating new Vecs.
/// The output buffer must contain exactly `num_channels` `Vec<T>` elements.
/// Each Vec will be cleared and filled with samples.
///
/// # Arguments
///
/// * `data` - Interleaved audio data
/// * `num_channels` - Number of channels
/// * `output` - Pre-allocated output buffer with `num_channels` Vecs
///
/// # Panics
///
/// Panics if `num_channels` is 0, if `data.len()` is not divisible by `num_channels`,
/// or if `output.len() != num_channels`.
///
/// # Example
///
/// ```
/// use stft_rs::deinterleave_into;
///
/// let interleaved = vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]; // L,R,L,R,L,R
/// let mut output = vec![Vec::new(), Vec::new()];
///
/// deinterleave_into(&interleaved, 2, &mut output);
///
/// assert_eq!(output[0], vec![1.0, 3.0, 5.0]); // Left
/// assert_eq!(output[1], vec![2.0, 4.0, 6.0]); // Right
/// ```
pub fn deinterleave_into<T: Float>(data: &[T], num_channels: usize, output: &mut [Vec<T>]) {
    assert!(num_channels > 0, "num_channels must be greater than 0");
    assert_eq!(
        output.len(),
        num_channels,
        "output must have exactly {} channels, got {}",
        num_channels,
        output.len()
    );
    assert_eq!(
        data.len() % num_channels,
        0,
        "data length ({}) must be divisible by num_channels ({})",
        data.len(),
        num_channels
    );

    if data.is_empty() {
        for channel in output.iter_mut() {
            channel.clear();
        }
        return;
    }

    let samples_per_channel = data.len() / num_channels;

    // Clear and reserve capacity
    for channel in output.iter_mut() {
        channel.clear();
        channel.reserve(samples_per_channel);
    }

    // Deinterleave
    for (i, &sample) in data.iter().enumerate() {
        output[i % num_channels].push(sample);
    }
}

/// Interleave multiple channels into a single buffer.
///
/// Converts separate channels (`vec![vec![L,L,L,...], vec![R,R,R,...]]`)
/// into interleaved format (e.g., `[L,R,L,R,L,R,...]` for stereo).
///
/// # Arguments
///
/// * `channels` - Vector of audio channels
///
/// # Panics
///
/// Panics if channels is empty or if channels have different lengths.
///
/// # Example
///
/// ```
/// use stft_rs::interleave;
///
/// let left = vec![1.0, 3.0, 5.0];
/// let right = vec![2.0, 4.0, 6.0];
/// let interleaved = interleave(&[left, right]);
///
/// assert_eq!(interleaved, vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]);
/// ```
pub fn interleave<T: Float>(channels: &[Vec<T>]) -> Vec<T> {
    assert!(!channels.is_empty(), "channels must not be empty");

    if channels[0].is_empty() {
        return Vec::new();
    }

    let num_channels = channels.len();
    let samples_per_channel = channels[0].len();

    // Validate all channels have same length
    for (i, channel) in channels.iter().enumerate() {
        assert_eq!(
            channel.len(),
            samples_per_channel,
            "Channel {} has length {}, expected {}",
            i,
            channel.len(),
            samples_per_channel
        );
    }

    let mut interleaved = Vec::with_capacity(samples_per_channel * num_channels);

    for sample_idx in 0..samples_per_channel {
        for channel in channels {
            interleaved.push(channel[sample_idx]);
        }
    }

    interleaved
}

/// Interleave multiple channels into a pre-allocated buffer (zero-allocation).
///
/// Converts separate channels into interleaved format without allocating.
/// The output buffer must have capacity for `samples_per_channel × num_channels`.
///
/// # Arguments
///
/// * `channels` - Slice of audio channels
/// * `output` - Pre-allocated output buffer (will be cleared and filled)
///
/// # Panics
///
/// Panics if channels is empty or if channels have different lengths.
///
/// # Example
///
/// ```
/// use stft_rs::interleave_into;
///
/// let left = vec![1.0, 3.0, 5.0];
/// let right = vec![2.0, 4.0, 6.0];
///
/// let mut output = Vec::with_capacity(6);
/// interleave_into(&[left, right], &mut output);
///
/// assert_eq!(output, vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0]);
/// ```
pub fn interleave_into<T: Float>(channels: &[Vec<T>], output: &mut Vec<T>) {
    assert!(!channels.is_empty(), "channels must not be empty");

    if channels[0].is_empty() {
        output.clear();
        return;
    }

    let num_channels = channels.len();
    let samples_per_channel = channels[0].len();

    // Validate all channels have same length
    for (i, channel) in channels.iter().enumerate() {
        assert_eq!(
            channel.len(),
            samples_per_channel,
            "Channel {} has length {}, expected {}",
            i,
            channel.len(),
            samples_per_channel
        );
    }

    output.clear();
    output.reserve(samples_per_channel * num_channels);

    for sample_idx in 0..samples_per_channel {
        for channel in channels {
            output.push(channel[sample_idx]);
        }
    }
}