diff --git a/.gitignore b/.gitignore
index cd937fe..b3eeb66 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,5 @@
 .DS_Store
 /.build
-/Packages
 xcuserdata/
 DerivedData/
 .swiftpm/configuration/registries.json
diff --git a/Package.swift b/Package.swift
index a24ecaa..030afe0 100644
--- a/Package.swift
+++ b/Package.swift
@@ -9,35 +9,22 @@ let package = Package(
         // Products define the executables and libraries a package produces, making them visible to other packages.
         .library(
             name: "EcgSynKit",
-            targets: ["EcgSynKit"]),
+            targets: ["EcgSynKit"]
+        ),
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-algorithms", from: "1.2.0"),
-        // .package(url: "https://github.com/AudioKit/KissFFT.git", from: "1.0.0")
-        .package(path: "./Packages/KissFFT/")
+        .package(path: "./Packages/KissFFT/"),
+        .package(path: "./Packages/PFFFT/"),
     ],
     targets: [
-        // Targets are the basic building blocks of a package, defining a module or a test suite.
-        // Targets can depend on other targets in this package and products from dependencies.
         .target(
-          name: "PFFFT",
-          publicHeadersPath: "include",
-            cSettings: [
-                .define("PFFFT_SCALVEC_ENABLED", to: "1"),
-                .define("_USE_MATH_DEFINES"),
-                .define("NDEBUG"),
-                .unsafeFlags(["-O3", "-std=c99"]),
-                .unsafeFlags(["-mavx"], .when(platforms: [.linux, .macOS])),
+            name: "EcgSynKit",
+            dependencies: [
+                .product(name: "PFFFT", package: "PFFFT"),
+                .product(name: "Algorithms", package: "swift-algorithms"),
             ]
         ),
-        .target(
-          name: "EcgSynKit",
-          dependencies: [
-            .target(name: "PFFFT"),
-            .product(name: "Algorithms", package: "swift-algorithms"),
-            .product(name: "KissFFT", package: "kissfft")
-          ]
-        ),
         .testTarget(
             name: "EcgSynKitTests",
             dependencies: ["EcgSynKit"]
diff --git a/Packages/PFFFT/.gitignore b/Packages/PFFFT/.gitignore
new file mode 100644
index 0000000..0023a53
--- /dev/null
+++ b/Packages/PFFFT/.gitignore
@@ -0,0 +1,8 @@
+.DS_Store
+/.build
+/Packages
+xcuserdata/
+DerivedData/
+.swiftpm/configuration/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc
diff --git a/Packages/PFFFT/Package.swift b/Packages/PFFFT/Package.swift
new file mode 100644
index 0000000..6b05beb
--- /dev/null
+++ b/Packages/PFFFT/Package.swift
@@ -0,0 +1,35 @@
+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "PFFFT",
+    products: [
+        // Products define the executables and libraries a package produces, making them visible to other packages.
+        .library(
+            name: "PFFFT",
+            targets: ["PFFFT", "PFFFTLib"]
+        ),
+    ],
+    targets: [
+        .target(
+            name: "PFFFTLib",
+            publicHeadersPath: "include",
+            cSettings: [
+                .define("PFFFT_SCALVEC_ENABLED", to: "1"),
+                .define("_USE_MATH_DEFINES"),
+                .define("NDEBUG"),
+                .unsafeFlags(["-O3", "-std=c99"]),
+            ]
+        ),
+        .target(
+            name: "PFFFT",
+            dependencies: ["PFFFTLib"]
+        ),
+        .testTarget(
+            name: "PFFFTTests",
+            dependencies: ["PFFFTLib"]
+        ),
+    ]
+)
diff --git a/Packages/PFFFT/Sources/PFFFT/Buffer.swift b/Packages/PFFFT/Sources/PFFFT/Buffer.swift
new file mode 100644
index 0000000..d602ba2
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFT/Buffer.swift
@@ -0,0 +1,29 @@
+let bufferAlignment = 32
+
+@frozen
+public struct Buffer<Element>: ~Copyable {
+    let buffer: UnsafeMutableBufferPointer<Element>
+
+    init(unsafeUninitializedCapacity: Int) {
+        buffer = UnsafeMutableRawBufferPointer.allocate(
+            byteCount: MemoryLayout<Element>.stride * unsafeUninitializedCapacity,
+            alignment: bufferAlignment
+        ).bindMemory(to: Element.self)
+    }
+
+    deinit {
+        buffer.deallocate()
+    }
+
+    func withUnsafeMutableBufferPointer<R>(_ body: (UnsafeMutableBufferPointer<Element>) throws -> R) rethrows -> R {
+        try body(buffer)
+    }
+
+    func withUnsafeBufferPointer<R>(_ body: (UnsafeBufferPointer<Element>) throws -> R) rethrows -> R {
+        try body(UnsafeBufferPointer(buffer))
+    }
+
+    func withUnsafeMutableBytes<R>(_ body: (UnsafeMutableRawBufferPointer) throws -> R) rethrows -> R {
+        try body(UnsafeMutableRawBufferPointer(buffer))
+    }
+}
diff --git a/Packages/PFFFT/Sources/PFFFT/FFTDoubleImpl.swift b/Packages/PFFFT/Sources/PFFFT/FFTDoubleImpl.swift
new file mode 100644
index 0000000..172aefb
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFT/FFTDoubleImpl.swift
@@ -0,0 +1,57 @@
+internal import PFFFTLib
+
+struct FFTDoubleImpl: FFTImplProtocol {
+    let ptr: OpaquePointer
+
+    init?(n: Int, type: FFTType) {
+        guard let ptr = pffftd_new_setup(Int32(n), pffft_transform_t(type)) else {
+            return nil
+        }
+        self.ptr = ptr
+    }
+
+    func fft(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, work: borrowing Buffer<Double>?, sign: FFTSign) {
+        let work: UnsafeMutablePointer<Double>! = switch work {
+        case let .some(b): b.buffer.baseAddress
+        case .none: nil
+        }
+
+        pffftd_transform_ordered(ptr, input.buffer.baseAddress, output.buffer.baseAddress, work, pffft_direction_t(sign))
+    }
+
+    func fftUnordered(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, work: borrowing Buffer<Double>?, sign: FFTSign) {
+        let work: UnsafeMutablePointer<Double>! = switch work {
+        case let .some(b): b.buffer.baseAddress
+        case .none: nil
+        }
+        pffftd_transform(ptr, input.buffer.baseAddress, output.buffer.baseAddress, work, pffft_direction_t(sign))
+    }
+
+    func zReorder(input: borrowing Buffer<Double>, output: borrowing Buffer<Double>, sign: FFTSign) {
+        pffftd_zreorder(ptr, input.buffer.baseAddress, output.buffer.baseAddress, pffft_direction_t(sign))
+    }
+
+    func zConvolveAccumulate(dftA: borrowing Buffer<Double>, dftB: borrowing Buffer<Double>, dftAB: borrowing Buffer<Double>, scaling: Double) {
+        pffftd_zconvolve_accumulate(ptr, dftA.buffer.baseAddress, dftB.buffer.baseAddress, dftAB.buffer.baseAddress, scaling)
+    }
+
+    func zConvolve(dftA: borrowing Buffer<Double>, dftB: borrowing Buffer<Double>, dftAB: borrowing Buffer<Double>, scaling: Double) {
+        pffftd_zconvolve_no_accu(ptr, dftA.buffer.baseAddress, dftB.buffer.baseAddress, dftAB.buffer.baseAddress, scaling)
+    }
+
+    func minFftSize(for type: FFTType) -> Int {
+        Int(pffftd_min_fft_size(pffft_transform_t(type)))
+    }
+
+    static func isValidSize(_ n: Int, for type: FFTType) -> Bool {
+        pffftd_is_valid_size(Int32(n), pffft_transform_t(type)) != 0
+    }
+
+    static func nearestValidSize(_ n: Int, for type: FFTType, higher: Bool) -> Int {
+        Int(pffftd_nearest_transform_size(Int32(n), pffft_transform_t(type), higher ? 1 : 0))
+    }
+
+    static func simdArch() -> String {
+        String(cString: pffftd_simd_arch())
+    }
+}
diff --git a/Packages/PFFFT/Sources/PFFFT/FFTFloatImpl.swift b/Packages/PFFFT/Sources/PFFFT/FFTFloatImpl.swift
new file mode 100644
index 0000000..ef6d897
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFT/FFTFloatImpl.swift
@@ -0,0 +1,57 @@
+internal import PFFFTLib
+
+struct FFTFloatImpl: FFTImplProtocol {
+    let ptr: OpaquePointer
+
+    init?(n: Int, type: FFTType) {
+        guard let ptr = pffft_new_setup(Int32(n), pffft_transform_t(type)) else {
+            return nil
+        }
+        self.ptr = ptr
+    }
+
+    func fft(input: borrowing Buffer<Float>, output: borrowing Buffer<Float>, work: borrowing Buffer<Float>?, sign: FFTSign) {
+        let work: UnsafeMutablePointer<Float>! = switch work {
+        case let .some(b): b.buffer.baseAddress
+        case .none: nil
+        }
+
+        pffft_transform_ordered(ptr, input.buffer.baseAddress, output.buffer.baseAddress, work, pffft_direction_t(sign))
+    }
+
+    func fftUnordered(input: borrowing Buffer<Float>, output: borrowing Buffer<Float>, work: borrowing Buffer<Float>?, sign: FFTSign) {
+        let work: UnsafeMutablePointer<Float>! = switch work {
+        case let .some(b): b.buffer.baseAddress
+        case .none: nil
+        }
+        pffft_transform(ptr, input.buffer.baseAddress, output.buffer.baseAddress, work, pffft_direction_t(sign))
+    }
+
+    func zReorder(input: borrowing Buffer<Float>, output: borrowing Buffer<Float>, sign: FFTSign) {
+        pffft_zreorder(ptr, input.buffer.baseAddress, output.buffer.baseAddress, pffft_direction_t(sign))
+    }
+
+    func zConvolveAccumulate(dftA: borrowing Buffer<Float>, dftB: borrowing Buffer<Float>, dftAB: borrowing Buffer<Float>, scaling: Float) {
+        pffft_zconvolve_accumulate(ptr, dftA.buffer.baseAddress, dftB.buffer.baseAddress, dftAB.buffer.baseAddress, scaling)
+    }
+
+    func zConvolve(dftA: borrowing Buffer<Float>, dftB: borrowing Buffer<Float>, dftAB: borrowing Buffer<Float>, scaling: Float) {
+        pffft_zconvolve_no_accu(ptr, dftA.buffer.baseAddress, dftB.buffer.baseAddress, dftAB.buffer.baseAddress, scaling)
+    }
+
+    func minFftSize(for type: FFTType) -> Int {
+        Int(pffft_min_fft_size(pffft_transform_t(type)))
+    }
+
+    static func isValidSize(_ n: Int, for type: FFTType) -> Bool {
+        pffft_is_valid_size(Int32(n), pffft_transform_t(type)) != 0
+    }
+
+    static func nearestValidSize(_ n: Int, for type: FFTType, higher: Bool) -> Int {
+        Int(pffft_nearest_transform_size(Int32(n), pffft_transform_t(type), higher ? 1 : 0))
+    }
+
+    static func simdArch() -> String {
+        String(cString: pffft_simd_arch())
+    }
+}
diff --git a/Packages/PFFFT/Sources/PFFFT/PFFFT.swift b/Packages/PFFFT/Sources/PFFFT/PFFFT.swift
new file mode 100644
index 0000000..87688ab
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFT/PFFFT.swift
@@ -0,0 +1,47 @@
+internal import PFFFTLib
+
+enum FFTType {
+    case real
+    case complex
+}
+
+enum FFTSign: Int  {
+    case forward = -1
+    case backward = 1
+}
+
+protocol FFTImplProtocol {
+    associatedtype Element
+
+    init?(n: Int, type: FFTType)
+
+    func fft(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?, sign: FFTSign)
+    func fftUnordered(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, work: borrowing Buffer<Element>?, sign: FFTSign)
+    func zReorder(input: borrowing Buffer<Element>, output: borrowing Buffer<Element>, sign: FFTSign)
+    func zConvolveAccumulate(dftA: borrowing Buffer<Element>, dftB: borrowing Buffer<Element>, dftAB: borrowing Buffer<Element>, scaling: Element)
+    func zConvolve(dftA: borrowing Buffer<Element>, dftB: borrowing Buffer<Element>, dftAB: borrowing Buffer<Element>, scaling: Element)
+    func minFftSize(for type: FFTType) -> Int
+    static func isValidSize(_ n: Int, for type: FFTType) -> Bool
+    static func nearestValidSize(_ n: Int, for type: FFTType, higher: Bool) -> Int
+    static func simdArch() -> String
+}
+
+extension pffft_transform_t {
+    @inline(__always)
+    init(_ type: FFTType) {
+        switch type {
+        case .real: self = PFFFT_REAL
+        case .complex: self = PFFFT_COMPLEX
+        }
+    }
+}
+
+extension pffft_direction_t {
+    @inline(__always)
+    init(_ sign: FFTSign) {
+        switch sign {
+        case .forward: self = PFFFT_FORWARD
+        case .backward: self = PFFFT_BACKWARD
+        }
+    }
+}
diff --git a/Packages/PFFFT/Sources/PFFFT/SetupCache.swift b/Packages/PFFFT/Sources/PFFFT/SetupCache.swift
new file mode 100644
index 0000000..e45afb3
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFT/SetupCache.swift
@@ -0,0 +1,30 @@
+import Foundation
+
+struct CacheKey : Hashable {
+    let n: Int
+    let type: FFTType
+}
+
+class SetupCache<Impl: FFTImplProtocol> : @unchecked Sendable {
+    private var cache: [CacheKey: Impl?] = [:]
+
+    private let queue = DispatchQueue(label: String(describing: SetupCache.self), attributes: .concurrent)
+
+    func get(for n: Int, type: FFTType) -> Impl? {
+        var setup: Impl??
+        queue.sync {
+            setup = cache[CacheKey(n: n, type: type)]
+        }
+        if setup == nil {
+            queue.sync(flags: .barrier) {
+                setup = cache[CacheKey(n: n, type: type)]
+                if setup == nil {
+                    setup = Impl(n: n, type: type)
+                    cache[CacheKey(n: n, type: type)] = setup
+                }
+            }
+        }
+        return setup!
+    }
+
+}
diff --git a/Sources/PFFFT/pffft.h b/Packages/PFFFT/Sources/PFFFTLib/include/pffft.h
similarity index 100%
rename from Sources/PFFFT/pffft.h
rename to Packages/PFFFT/Sources/PFFFTLib/include/pffft.h
diff --git a/Sources/PFFFT/include/pffft_double.h b/Packages/PFFFT/Sources/PFFFTLib/include/pffft_double.h
similarity index 100%
rename from Sources/PFFFT/include/pffft_double.h
rename to Packages/PFFFT/Sources/PFFFTLib/include/pffft_double.h
diff --git a/Packages/PFFFT/Sources/PFFFTLib/pffft.c b/Packages/PFFFT/Sources/PFFFTLib/pffft.c
new file mode 100644
index 0000000..4862a4f
--- /dev/null
+++ b/Packages/PFFFT/Sources/PFFFTLib/pffft.c
@@ -0,0 +1,134 @@
+/* Copyright (c) 2013  Julien Pommier ( pommier@modartt.com )
+   Copyright (c) 2020  Hayati Ayguen ( h_ayguen@web.de )
+
+   Based on original fortran 77 code from FFTPACKv4 from NETLIB
+   (http://www.netlib.org/fftpack), authored by Dr Paul Swarztrauber
+   of NCAR, in 1985.
+
+   As confirmed by the NCAR fftpack software curators, the following
+   FFTPACKv5 license applies to FFTPACKv4 sources. My changes are
+   released under the same terms.
+
+   FFTPACK license:
+
+   http://www.cisl.ucar.edu/css/software/fftpack5/ftpk.html
+
+   Copyright (c) 2004 the University Corporation for Atmospheric
+   Research ("UCAR"). All rights reserved. Developed by NCAR's
+   Computational and Information Systems Laboratory, UCAR,
+   www.cisl.ucar.edu.
+
+   Redistribution and use of the Software in source and binary forms,
+   with or without modification, is permitted provided that the
+   following conditions are met:
+
+   - Neither the names of NCAR's Computational and Information Systems
+   Laboratory, the University Corporation for Atmospheric Research,
+   nor the names of its sponsors or contributors may be used to
+   endorse or promote products derived from this Software without
+   specific prior written permission.  
+
+   - Redistributions of source code must retain the above copyright
+   notices, this list of conditions, and the disclaimer below.
+
+   - Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions, and the disclaimer below in the
+   documentation and/or other materials provided with the
+   distribution.
+
+   THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+   EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO THE WARRANTIES OF
+   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+   NONINFRINGEMENT. IN NO EVENT SHALL THE CONTRIBUTORS OR COPYRIGHT
+   HOLDERS BE LIABLE FOR ANY CLAIM, INDIRECT, INCIDENTAL, SPECIAL,
+   EXEMPLARY, OR CONSEQUENTIAL DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+   SOFTWARE.
+
+
+   PFFFT : a Pretty Fast FFT.
+
+   This file is largerly based on the original FFTPACK implementation, modified in
+   order to take advantage of SIMD instructions of modern CPUs.
+*/
+
+/*
+  ChangeLog: 
+  - 2011/10/02, version 1: This is the very first release of this file.
+*/
+
+#include "pffft.h"
+
+/* detect compiler flavour */
+#if defined(_MSC_VER)
+#  define COMPILER_MSVC
+#elif defined(__GNUC__)
+#  define COMPILER_GCC
+#endif
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <math.h>
+#include <assert.h>
+
+#if defined(COMPILER_GCC)
+#  define ALWAYS_INLINE(return_type) inline return_type __attribute__ ((always_inline))
+#  define NEVER_INLINE(return_type) return_type __attribute__ ((noinline))
+#  define RESTRICT __restrict
+#  define VLA_ARRAY_ON_STACK(type__, varname__, size__) type__ varname__[size__];
+#elif defined(COMPILER_MSVC)
+#  define ALWAYS_INLINE(return_type) __forceinline return_type
+#  define NEVER_INLINE(return_type) __declspec(noinline) return_type
+#  define RESTRICT __restrict
+#  define VLA_ARRAY_ON_STACK(type__, varname__, size__) type__ *varname__ = (type__*)_alloca(size__ * sizeof(type__))
+#endif
+
+
+#ifdef COMPILER_MSVC
+#pragma warning( disable : 4244 4305 4204 4456 )
+#endif
+
+/* 
+   vector support macros: the rest of the code is independant of
+   SSE/Altivec/NEON -- adding support for other platforms with 4-element
+   vectors should be limited to these macros 
+*/
+#include "simd/pf_float.h"
+
+/* have code comparable with this definition */
+#define SETUP_STRUCT               PFFFT_Setup
+#define FUNC_NEW_SETUP             pffft_new_setup
+#define FUNC_DESTROY               pffft_destroy_setup
+#define FUNC_TRANSFORM_UNORDRD     pffft_transform
+#define FUNC_TRANSFORM_ORDERED     pffft_transform_ordered
+#define FUNC_ZREORDER              pffft_zreorder
+#define FUNC_ZCONVOLVE_ACCUMULATE  pffft_zconvolve_accumulate
+#define FUNC_ZCONVOLVE_NO_ACCU     pffft_zconvolve_no_accu
+
+#define FUNC_ALIGNED_MALLOC        pffft_aligned_malloc
+#define FUNC_ALIGNED_FREE          pffft_aligned_free
+#define FUNC_SIMD_SIZE             pffft_simd_size
+#define FUNC_MIN_FFT_SIZE          pffft_min_fft_size
+#define FUNC_IS_VALID_SIZE         pffft_is_valid_size
+#define FUNC_NEAREST_SIZE          pffft_nearest_transform_size
+#define FUNC_SIMD_ARCH             pffft_simd_arch
+#define FUNC_VALIDATE_SIMD_A       validate_pffft_simd
+#define FUNC_VALIDATE_SIMD_EX      validate_pffft_simd_ex
+
+#define FUNC_CPLX_FINALIZE         pffft_cplx_finalize
+#define FUNC_CPLX_PREPROCESS       pffft_cplx_preprocess
+#define FUNC_REAL_PREPROCESS_4X4   pffft_real_preprocess_4x4
+#define FUNC_REAL_PREPROCESS       pffft_real_preprocess
+#define FUNC_REAL_FINALIZE_4X4     pffft_real_finalize_4x4
+#define FUNC_REAL_FINALIZE         pffft_real_finalize
+#define FUNC_TRANSFORM_INTERNAL    pffft_transform_internal
+
+#define FUNC_COS  cosf
+#define FUNC_SIN  sinf
+
+
+#include "pffft_priv_impl.h"
+
+
diff --git a/Sources/PFFFT/pffft_common.c b/Packages/PFFFT/Sources/PFFFTLib/pffft_common.c
similarity index 100%
rename from Sources/PFFFT/pffft_common.c
rename to Packages/PFFFT/Sources/PFFFTLib/pffft_common.c
diff --git a/Sources/PFFFT/pffft_double.c b/Packages/PFFFT/Sources/PFFFTLib/pffft_double.c
similarity index 100%
rename from Sources/PFFFT/pffft_double.c
rename to Packages/PFFFT/Sources/PFFFTLib/pffft_double.c
diff --git a/Sources/PFFFT/pffft_priv_impl.h b/Packages/PFFFT/Sources/PFFFTLib/pffft_priv_impl.h
similarity index 100%
rename from Sources/PFFFT/pffft_priv_impl.h
rename to Packages/PFFFT/Sources/PFFFTLib/pffft_priv_impl.h
diff --git a/Sources/PFFFT/simd/pf_altivec_float.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_altivec_float.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_altivec_float.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_altivec_float.h
diff --git a/Sources/PFFFT/simd/pf_avx_double.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_avx_double.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_avx_double.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_avx_double.h
diff --git a/Sources/PFFFT/simd/pf_double.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_double.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_double.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_double.h
diff --git a/Sources/PFFFT/simd/pf_float.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_float.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_float.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_float.h
diff --git a/Sources/PFFFT/simd/pf_neon_double.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_neon_double.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_neon_double.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_neon_double.h
diff --git a/Sources/PFFFT/simd/pf_neon_double_from_avx.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_neon_double_from_avx.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_neon_double_from_avx.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_neon_double_from_avx.h
diff --git a/Sources/PFFFT/simd/pf_neon_float.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_neon_float.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_neon_float.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_neon_float.h
diff --git a/Sources/PFFFT/simd/pf_scalar_double.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_scalar_double.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_scalar_double.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_scalar_double.h
diff --git a/Sources/PFFFT/simd/pf_scalar_float.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_scalar_float.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_scalar_float.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_scalar_float.h
diff --git a/Sources/PFFFT/simd/pf_sse1_float.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_sse1_float.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_sse1_float.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_sse1_float.h
diff --git a/Sources/PFFFT/simd/pf_sse2_double.h b/Packages/PFFFT/Sources/PFFFTLib/simd/pf_sse2_double.h
similarity index 100%
rename from Sources/PFFFT/simd/pf_sse2_double.h
rename to Packages/PFFFT/Sources/PFFFTLib/simd/pf_sse2_double.h
diff --git a/Packages/PFFFT/Tests/PFFFTTests/PFFFTTests.swift b/Packages/PFFFT/Tests/PFFFTTests/PFFFTTests.swift
new file mode 100644
index 0000000..1ca34d3
--- /dev/null
+++ b/Packages/PFFFT/Tests/PFFFTTests/PFFFTTests.swift
@@ -0,0 +1,6 @@
+import Testing
+@testable import PFFFT
+
+@Test func example() async throws {
+    // Write your test here and use APIs like `#expect(...)` to check expected conditions.
+}
diff --git a/Sources/EcgSynKit/EcgSynKit.swift b/Sources/EcgSynKit/EcgSynKit.swift
index d2ab6d1..a3c1b29 100644
--- a/Sources/EcgSynKit/EcgSynKit.swift
+++ b/Sources/EcgSynKit/EcgSynKit.swift
@@ -1,6 +1,6 @@
 import Algorithms
 import Foundation
-import PFFFT
+import PFFFTLib
 
 struct Parameters {
     /// The number of beats to simulate.
@@ -85,6 +85,10 @@ class PfftSetupCache: @unchecked Sendable {
     static let shared = PfftSetupCache()
 }
 
+struct EcgDerive {
+    let rrpc: [Double]
+}
+
 func stdev(_ data: [Double]) -> Double {
     let n = Double(data.count)
     let mean = data.reduce(0.0, +) / n
diff --git a/Tests/EcgSynKitTests/EcgSynKitTests.swift b/Tests/EcgSynKitTests/EcgSynKitTests.swift
index dc2434e..e18059b 100644
--- a/Tests/EcgSynKitTests/EcgSynKitTests.swift
+++ b/Tests/EcgSynKitTests/EcgSynKitTests.swift
@@ -1,6 +1,5 @@
 import Testing
 @testable import EcgSynKit
-@testable import KissFFT
 
 @Test func fftTest ()  {
     // Write your test here and use APIs like `#expect(...)` to check expected conditions.