Staging 0.5.0

.github/workflows/rust.yml

@@ -10,13 +10,40 @@ env:
   CARGO_TERM_COLOR: always
 
 jobs:
-  build:
-
+  # Test with default features (std + rustfft)
+  test-rustfft:
     runs-on: ubuntu-latest
-
     steps:
     - uses: actions/checkout@v4
-    - name: Build
+    - name: Build with rustfft (default)
       run: cargo build --verbose
-    - name: Run tests
+    - name: Run tests with rustfft
       run: cargo test --verbose
+    - name: Run tests with rayon
+      run: cargo test --verbose --features rayon
+
+  # Test with microfft backend (no_std)
+  test-microfft:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Build with microfft (no_std)
+      run: cargo build --no-default-features --features microfft-backend --verbose
+    - name: Run tests with microfft
+      run: cargo test --no-default-features --features microfft-backend --verbose
+    - name: Check lib compiles in no_std
+      run: cargo check --no-default-features --features microfft-backend --lib
+
+  # Compare both backends to ensure identical behavior
+  backend-comparison:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Run backend comparison script
+      run: ./scripts/compare_backends.sh
+    - name: Upload comparison results
+      if: always()
+      uses: actions/upload-artifact@v4
+      with:
+        name: backend-comparison-results
+        path: results_*.txt

.gitignore

@@ -1 +1,5 @@
 /target
+*.png
+results_microfft.txt
+results_rustfft.txt
+no_std_test/target

Cargo.toml

@@ -1,20 +1,24 @@
 [package]
 name = "stft-rs"
-description = "Simple, streaming-friendly STFT implementation with mel spectrogram support"
-version = "0.4.1"
+description = "Simple, streaming-friendly, no_std compliant STFT implementation with mel spectrogram support"
+version = "0.5.0"
 edition = "2024"
 authors = ["David Maseda Neira <david.masedan@gmail.com>"]
 license = "MIT"
 repository = "https://github.com/wizenink/stft-rs"
 
 [dependencies]
-ndarray = "0.17.1"
-num-traits = "0.2"
-rustfft = "6.4.1"
+num-traits = { version = "0.2", default-features = false, features = ["libm"] }
+rustfft = { version = "6.4.1", optional = true }
+microfft = { version = "0.6.0", optional = true }
 rayon = { version = "1.11", optional = true }
 
 [features]
-default = ["rayon"]
+default = ["std"]
+std = ["num-traits/std", "rustfft-backend"]
+rustfft-backend = ["dep:rustfft"]
+microfft-backend = ["dep:microfft"]
+rayon = ["rustfft-backend", "dep:rayon"]
 
 [dev-dependencies]
 criterion = { version = "0.7.0", features = ["html_reports"] }

README.md

@@ -12,6 +12,10 @@ High-quality, streaming-friendly STFT/iSTFT implementation in Rust working with
 - **Batch Processing**: Process entire audio buffers at once
 - **Streaming Support**: Incremental processing for real-time applications
 - **High Quality**: >138 dB SNR reconstruction
+- **no_std Support**: Run on embedded systems without the standard library! 🚀
+  - **Dual FFT Backends**: Choose the right backend for your environment
+    - `rustfft` (default): Full-featured for std environments, supports f32/f64 and any FFT size
+    - `microfft`: Lightweight for no_std/embedded, f32 only, power-of-2 sizes up to 4096
 - **Dual Reconstruction Modes**:
   - **OLA** (Overlap-Add): Optimal for spectral processing
   - **WOLA** (Weighted Overlap-Add): Standard implementation
@@ -112,7 +116,7 @@ use stft_rs::prelude::*;
 
 This exports:
 
-- Core types: `BatchStft`, `BatchIstft`, `StreamingStft`, `StreamingIstft`, `StftConfig`, `StftConfigBuilder`, `Spectrum`, `SpectrumFrame`
+- Core types: `BatchStft`, `BatchIstft`, `StreamingStft`, `StreamingIstft`, `StftConfig`, `StftConfigBuilder`, `Spectrum`, `SpectrumFrame`, `Complex`
 - Type aliases: `StftConfigF32/F64`, `StftConfigBuilderF32/F64`, `BatchStftF32/F64`, `BatchIstftF32/F64`, `StreamingStftF32/F64`, `StreamingIstftF32/F64`, `SpectrumF32/F64`, `SpectrumFrameF32/F64`
 - Mel types: `MelConfig`, `MelSpectrum`, `BatchMelSpectrogram`, `StreamingMelSpectrogram`, `MelScale`, `MelNorm` (+ F32/F64 aliases)
 - Enums: `ReconstructionMode`, `WindowType`, `PadMode`
@@ -404,10 +408,58 @@ let channels = deinterleave(&interleaved, 2);
 let interleaved = interleave(&channels);
 ```
 
-Disable parallel processing: `cargo build --no-default-features`
-
 See `examples/multichannel_stereo.rs` and `examples/multichannel_midside.rs` for more.
 
+## Embedded / no_std Support
+
+stft-rs can run on embedded systems without the standard library! Perfect for audio processing on microcontrollers, DSPs, and bare-metal environments.
+
+### Using the microfft Backend for no_std
+
+```toml
+[dependencies]
+stft-rs = { version = "0.4", default-features = false, features = ["microfft-backend"] }
+```
+
+**Important notes:**
+
+- microfft backend only supports f32 (not f64)
+- FFT sizes must be power-of-2 from 2 to 4096
+- Requires an allocator (uses `alloc` crate)
+
+### Example no_std Configuration
+
+```rust
+#![no_std]
+
+extern crate alloc;
+use alloc::vec::Vec;
+use stft_rs::prelude::*;
+
+// Works great on embedded!
+let config = StftConfigF32::builder()
+    .fft_size(2048)  // Must be power-of-2
+    .hop_size(512)
+    .build()
+    .expect("Valid config");
+
+let stft = BatchStftF32::new(config.clone());
+let istft = BatchIstftF32::new(config);
+
+let signal: Vec<f32> = Vec::from_slice(&audio_buffer);
+let spectrum = stft.process(&signal);
+let reconstructed = istft.process(&spectrum);
+```
+
+### Feature Flags
+
+- `std` (default): Standard library support with rustfft backend
+- `rustfft-backend`: Use rustfft for FFT (supports f32/f64, any size)
+- `microfft-backend`: Use microfft for no_std (f32 only, power-of-2 sizes)
+- `rayon`: Enable parallel multi-channel processing (requires std)
+
+**Note:** You cannot enable both `rustfft-backend` and `microfft-backend` at the same time.
+
 ## Performance Characteristics
 
 - **Batch Mode**: Optimized for throughput, minimal allocations
@@ -517,8 +569,18 @@ Tests verify:
 
 ## Dependencies
 
-- `rustfft`: High-performance FFT implementation
-- `ndarray`: Only for internal padding operations (minimal usage)
+Core dependencies:
+
+- `num-traits`: Generic numeric traits (no_std compatible with `libm`)
+
+FFT backends (mutually exclusive):
+
+- `rustfft` (default): High-performance FFT for std environments
+- `microfft` (optional): Lightweight FFT for no_std/embedded
+
+Optional dependencies:
+
+- `rayon`: Parallel multi-channel processing (requires std)
 
 ## License