CMakeLists: build for x86-64-v3 by default

.github/workflows/build.yml

@@ -6,6 +6,11 @@ on:
   pull_request:
     branches: [main, master]
 
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
 jobs:
   linux:
     name: Linux (static)
@@ -39,9 +44,16 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Cache vcpkg packages
+        uses: actions/cache@v4
+        with:
+          path: ${{ env.VCPKG_INSTALLATION_ROOT }}/installed
+          key: vcpkg-x64-windows-${{ hashFiles('.github/workflows/build.yml') }}
+          restore-keys: vcpkg-x64-windows-
+
       - name: Install vcpkg dependencies
         run: |
-          vcpkg install sdl2 fftw3 libsndfile --triplet x64-windows
+          vcpkg install sdl2 fftw3 "libsndfile[core]" --triplet x64-windows
 
       - name: Configure
         run: >
@@ -88,3 +100,30 @@ jobs:
             build_wasm/web/baudmine.html
             build_wasm/web/baudmine.js
             build_wasm/web/baudmine.wasm
+
+      - name: Prepare Pages
+        if: github.event_name == 'push'
+        run: |
+          mkdir -p _site
+          cp build_wasm/web/baudmine.html _site/index.html
+          cp build_wasm/web/baudmine.js   _site/
+          cp build_wasm/web/baudmine.wasm _site/
+
+      - name: Upload Pages artifact
+        if: github.event_name == 'push'
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: _site
+
+  deploy:
+    name: Deploy to GitHub Pages
+    needs: wasm
+    if: github.event_name == 'push'
+    runs-on: ubuntu-24.04
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy
+        id: deployment
+        uses: actions/deploy-pages@v4

CMakeLists.txt

@@ -180,32 +180,53 @@ if(EMSCRIPTEN)
 else()
     # ── Native Build ─────────────────────────────────────────────────────────
 
-    set(CMAKE_CXX_FLAGS_RELEASE "-O3 -march=native -DNDEBUG")
-    set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -fsanitize=address,undefined")
+    option(NATIVE_BUILD "Optimize for the host CPU (-march=native)" OFF)
+
+    if(MSVC)
+        set(CMAKE_CXX_FLAGS_RELEASE "/O2 /DNDEBUG /arch:AVX2")
+        set(CMAKE_CXX_FLAGS_DEBUG "/Zi /Od")
+    else()
+        if(NATIVE_BUILD)
+            set(CMAKE_CXX_FLAGS_RELEASE "-O3 -march=native -DNDEBUG")
+        else()
+            set(CMAKE_CXX_FLAGS_RELEASE "-O3 -march=x86-64-v3 -DNDEBUG")
+        endif()
+        set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -fsanitize=address,undefined")
+    endif()
 
-    find_package(PkgConfig REQUIRED)
     find_package(OpenGL REQUIRED)
 
-    pkg_check_modules(SDL2 REQUIRED IMPORTED_TARGET sdl2)
-    pkg_check_modules(FFTW3F REQUIRED IMPORTED_TARGET fftw3f)
-    pkg_check_modules(SNDFILE REQUIRED IMPORTED_TARGET sndfile)
+    if(MSVC)
+        find_package(SDL2 CONFIG REQUIRED)
+        find_package(FFTW3f CONFIG REQUIRED)
+        find_package(SndFile CONFIG REQUIRED)
 
-    target_link_libraries(imgui PUBLIC PkgConfig::SDL2 OpenGL::GL)
+        target_link_libraries(imgui PUBLIC SDL2::SDL2 OpenGL::GL)
 
-    add_executable(baudmine ${SOURCES})
-    target_include_directories(baudmine PRIVATE src)
-    target_link_libraries(baudmine PRIVATE
-        imgui
-        PkgConfig::SDL2
-        PkgConfig::FFTW3F
-        PkgConfig::SNDFILE
-        OpenGL::GL
-        pthread
-    )
+        add_executable(baudmine ${SOURCES})
+        target_include_directories(baudmine PRIVATE src)
+        target_link_libraries(baudmine PRIVATE
+            imgui SDL2::SDL2 SDL2::SDL2main
+            FFTW3::fftw3f SndFile::sndfile OpenGL::GL
+        )
+    else()
+        find_package(PkgConfig REQUIRED)
+        pkg_check_modules(SDL2 REQUIRED IMPORTED_TARGET sdl2)
+        pkg_check_modules(FFTW3F REQUIRED IMPORTED_TARGET fftw3f)
+        pkg_check_modules(SNDFILE REQUIRED IMPORTED_TARGET sndfile)
 
-    # Link math library and dl on Unix (dl needed by miniaudio for backend loading)
-    if(UNIX)
-        target_link_libraries(baudmine PRIVATE m dl)
+        target_link_libraries(imgui PUBLIC PkgConfig::SDL2 OpenGL::GL)
+
+        add_executable(baudmine ${SOURCES})
+        target_include_directories(baudmine PRIVATE src)
+        target_link_libraries(baudmine PRIVATE
+            imgui PkgConfig::SDL2 PkgConfig::FFTW3F
+            PkgConfig::SNDFILE OpenGL::GL pthread
+        )
+
+        if(UNIX)
+            target_link_libraries(baudmine PRIVATE m dl)
+        endif()
     endif()
 
 endif()

LICENSE

@@ -0,0 +1,674 @@
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+                       Version 3, 29 June 2007
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+or that patent license was granted, prior to 28 March 2007.
+
+  Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+  12. No Surrender of Others' Freedom.
+
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+
+  13. Use with the GNU Affero General Public License.
+
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+
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+
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+
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+reviewing courts shall apply local law that most closely approximates
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+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
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+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
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+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.

README.md

@@ -0,0 +1,69 @@
+# Baudmine Spectrum Analyzer
+
+Real-time audio spectrum analyzer and waterfall display built with C++17, ImGui, SDL2, and OpenGL. Runs natively on Linux and Windows, and in the browser via WebAssembly.
+
+Beware, this thing is **entirely LLM-generated**! I've barely looked at the code! Anthropic had a promo for Claude, so I utilized it to make this clone of [**baudline**](https://www.baudline.com/what_is_baudline.html), which is a very powerful (and proprietary) tool, but sadly it's been seemingly abandoned for years, not that it would need anything. My hope was to put together something similar, using a more modern stack. It is not (yet) a fully-featured replacement, but it's good enough for me.
+
+## Web preview
+
+You can find the Web version here, delivered in 870 kB: https://ericek111.github.io/baudmine/
+
+(If you allow access to "all microphones", you can switch between the input devices in the File menu.)
+
+## Features
+
+### Signal Processing
+- FFT sizes from 256 to 65,536 points with configurable overlap of bins for precise speed control of the waterfall.
+- Window functions: Hann, Hamming, Blackman, Blackman-Harris, Kaiser (configurable beta), Flat Top, Rectangular
+
+### Input Sources
+- Live audio from system input devices
+- Multi-device mode: use up to 8 devices simultaneously, each mapped to a channel
+- File playback: WAV, Float32/Int16/Uint8 I/Q formats
+
+### Visualization
+- Spectrum plot
+- Scrolling waterfall display that can be zoomed and panned
+- Linear and logarithmic frequency scales
+- Additive color blending for multi-channel display
+- Peak hold with adjustable decay rate
+
+### Analysis
+- Dual cursors with frequency and magnitude readout
+- Automatic snap-to-peak
+- Peak detection with configurable threshold, separation, and frequency range (it shows the center frequency of the peak-detected FFT bin)
+- Peak trace on the waterfall
+- Delta measurements between cursors
+
+### Math Channels
+- Unary: Negate, Absolute, Square, Cube, Square Root, Log
+- Binary: Add, Subtract, Multiply, Phase, Cross-correlation
+- Custom colors per math channel
+
+### Interface
+- DPI-aware UI with auto-detection and manual scaling (100-300%)
+- Touch gesture support in the waterfall (pan and pinch-to-zoom)
+- The most important settings persist across sessions
+
+## Building
+
+### Linux
+
+```bash
+# Install dependencies (Debian/Ubuntu)
+sudo apt install build-essential cmake pkg-config libsdl2-dev libfftw3-dev libsndfile1-dev libgl-dev
+
+cmake -B build -DCMAKE_BUILD_TYPE=Release -DNATIVE_BUILD=ON
+cmake --build build -j$(nproc)
+```
+
+### Windows (MSVC + vcpkg)
+
+```powershell
+vcpkg install sdl2 fftw3 "libsndfile[core]" --triplet x64-windows
+
+cmake -B build -DCMAKE_BUILD_TYPE=Release -DNATIVE_BUILD=ON `
+    -DCMAKE_TOOLCHAIN_FILE="$env:VCPKG_INSTALLATION_ROOT/scripts/buildsystems/vcpkg.cmake" `
+    -DVCPKG_TARGET_TRIPLET=x64-windows
+cmake --build build --config Release
+```

src/audio/AudioEngine.cpp

@@ -2,6 +2,7 @@
 #include "audio/FileSource.h"
 
 #include <algorithm>
+#include <chrono>
 #include <cmath>
 #include <cstdio>
 #include <cstring>
@@ -146,6 +147,8 @@ void AudioEngine::clearHistory() {
     analyzer_.clearHistory();
     for (auto& ed : extraDevices_)
         ed->analyzer.clearHistory();
+    for (auto& mw : mathWaterfalls_)
+        mw.clear();
 }
 
 int AudioEngine::processAudio() {
@@ -157,19 +160,38 @@ int AudioEngine::processAudio() {
     if (hopFrames < 1) hopFrames = 1;
     audioBuf_.resize(hopFrames * channels);
 
-    constexpr int kMaxSpectraPerFrame = 8;
+    // Drain all available audio so the scroll rate is independent of the
+    // display refresh rate (vsync).  Real-time sources self-limit via their
+    // ring buffer; file sources are capped to wall-clock time so playback
+    // runs at 1× speed regardless of frame rate.
+
+    // For file sources, compute how many samples correspond to elapsed time.
+    size_t fileSampleCap = SIZE_MAX;  // unlimited for real-time
+    if (!audioSource_->isRealTime()) {
+        using Clock = std::chrono::steady_clock;
+        static Clock::time_point lastFileTime = Clock::now();
+        auto now = Clock::now();
+        double elapsed = std::chrono::duration<double>(now - lastFileTime).count();
+        lastFileTime = now;
+        // Clamp elapsed to avoid huge bursts after pauses or stalls.
+        if (elapsed > 0.1) elapsed = 0.1;
+        fileSampleCap = static_cast<size_t>(elapsed * settings_.sampleRate) + 1;
+    }
 
     // Process primary source.
     int spectraThisFrame = 0;
-    while (spectraThisFrame < kMaxSpectraPerFrame) {
+    size_t samplesRead = 0;
+    for (;;) {
+        if (samplesRead >= fileSampleCap) break;
         size_t framesRead = audioSource_->read(audioBuf_.data(), hopFrames);
         if (framesRead == 0) break;
+        samplesRead += framesRead;
         analyzer_.pushSamples(audioBuf_.data(), framesRead);
         if (analyzer_.hasNewSpectrum())
             ++spectraThisFrame;
     }
 
-    // Process extra devices independently.
+    // Process extra devices independently (always real-time).
     for (auto& ed : extraDevices_) {
         int edCh = ed->source->channels();
         const auto& edSettings = ed->analyzer.settings();
@@ -177,16 +199,17 @@ int AudioEngine::processAudio() {
         if (edHop < 1) edHop = 1;
         ed->audioBuf.resize(edHop * edCh);
 
-        int edSpectra = 0;
-        while (edSpectra < kMaxSpectraPerFrame) {
+        for (;;) {
             size_t framesRead = ed->source->read(ed->audioBuf.data(), edHop);
             if (framesRead == 0) break;
             ed->analyzer.pushSamples(ed->audioBuf.data(), framesRead);
-            if (ed->analyzer.hasNewSpectrum())
-                ++edSpectra;
         }
     }
 
+    // Track overruns: spectra lost because they exceeded the history capacity.
+    if (spectraThisFrame > kWaterfallHistory)
+        overrunCount_ += spectraThisFrame - kWaterfallHistory;
+
     return spectraThisFrame;
 }
 
@@ -226,6 +249,18 @@ const std::vector<float>& AudioEngine::getSpectrum(int globalCh) const {
     return analyzer_.channelSpectrum(0);
 }
 
+const std::deque<std::vector<float>>& AudioEngine::getWaterfallHistory(int globalCh) const {
+    int n = analyzer_.numSpectra();
+    if (globalCh < n) return analyzer_.waterfallHistory(globalCh);
+    globalCh -= n;
+    for (auto& ed : extraDevices_) {
+        int en = ed->analyzer.numSpectra();
+        if (globalCh < en) return ed->analyzer.waterfallHistory(globalCh);
+        globalCh -= en;
+    }
+    return analyzer_.waterfallHistory(0);
+}
+
 const std::vector<std::complex<float>>& AudioEngine::getComplex(int globalCh) const {
     int n = analyzer_.numSpectra();
     if (globalCh < n) return analyzer_.channelComplex(globalCh);
@@ -265,10 +300,17 @@ const char* AudioEngine::getDeviceName(int globalCh) const {
 
 // ── Math channels ────────────────────────────────────────────────────────────
 
+const std::deque<std::vector<float>>& AudioEngine::mathWaterfallHistory(int mi) const {
+    static const std::deque<std::vector<float>> empty;
+    if (mi < 0 || mi >= static_cast<int>(mathWaterfalls_.size())) return empty;
+    return mathWaterfalls_[mi];
+}
+
 void AudioEngine::computeMathChannels() {
     int nPhys = totalNumSpectra();
     int specSz = analyzer_.spectrumSize();
     mathSpectra_.resize(mathChannels_.size());
+    mathWaterfalls_.resize(mathChannels_.size());
 
     for (size_t mi = 0; mi < mathChannels_.size(); ++mi) {
         const auto& mc = mathChannels_[mi];
@@ -339,6 +381,11 @@ void AudioEngine::computeMathChannels() {
             }
             out[i] = val;
         }
+
+        // Push to math waterfall history.
+        mathWaterfalls_[mi].push_back(out);
+        if (mathWaterfalls_[mi].size() > kWaterfallHistory)
+            mathWaterfalls_[mi].pop_front();
     }
 }
 

src/audio/AudioEngine.h

@@ -6,6 +6,7 @@
 #include "dsp/SpectrumAnalyzer.h"
 
 #include <complex>
+#include <deque>
 #include <memory>
 #include <string>
 #include <vector>
@@ -42,6 +43,7 @@ public:
     // ── Unified channel view across all analyzers ──
     int totalNumSpectra() const;
     const std::vector<float>& getSpectrum(int globalCh) const;
+    const std::deque<std::vector<float>>& getWaterfallHistory(int globalCh) const;
     const std::vector<std::complex<float>>& getComplex(int globalCh) const;
     const char* getDeviceName(int globalCh) const;
     int spectrumSize() const { return analyzer_.spectrumSize(); }
@@ -51,8 +53,15 @@ public:
     std::vector<MathChannel>&       mathChannels()       { return mathChannels_; }
     const std::vector<MathChannel>& mathChannels() const { return mathChannels_; }
     const std::vector<std::vector<float>>& mathSpectra() const { return mathSpectra_; }
+    const std::deque<std::vector<float>>& mathWaterfallHistory(int mi) const;
     void computeMathChannels();
 
+    // ── Overrun tracking ──
+    // Counts spectra lost because more were produced in a single frame
+    // than the waterfall history deque can hold.
+    int  overrunCount() const { return overrunCount_; }
+    void resetOverrunCount()  { overrunCount_ = 0; }
+
     // ── Device selection state (for config persistence) ──
     int  deviceIdx()       const { return deviceIdx_; }
     void setDeviceIdx(int i)     { deviceIdx_ = i; }
@@ -79,8 +88,12 @@ private:
     AnalyzerSettings settings_;
 
     // Math
-    std::vector<MathChannel>        mathChannels_;
-    std::vector<std::vector<float>> mathSpectra_;
+    std::vector<MathChannel>                    mathChannels_;
+    std::vector<std::vector<float>>             mathSpectra_;
+    std::vector<std::deque<std::vector<float>>> mathWaterfalls_;
+
+    // Overrun
+    int overrunCount_ = 0;
 
     // Device state
     std::vector<MiniAudioSource::DeviceInfo> devices_;

src/core/Config.cpp

@@ -2,6 +2,9 @@
 #include <cstdlib>
 #include <fstream>
 #include <sstream>
+#ifndef __EMSCRIPTEN__
+#include <filesystem>
+#endif
 
 #ifdef __EMSCRIPTEN__
 #include <emscripten.h>
@@ -22,7 +25,6 @@ EM_JS(void, js_saveSettings, (const char* data), {
 });
 
 #else
-#include <sys/stat.h>
 #endif
 
 namespace baudmine {
@@ -30,16 +32,20 @@ namespace baudmine {
 std::string Config::defaultPath() {
 #ifdef __EMSCRIPTEN__
     return "";
+#elif defined(_WIN32)
+    const char* appdata = std::getenv("APPDATA");
+    auto base = std::filesystem::path(appdata ? appdata : ".");
+    return (base / "baudmine" / "settings.ini").string();
 #else
     const char* xdg = std::getenv("XDG_CONFIG_HOME");
-    std::string base;
+    std::filesystem::path base;
     if (xdg && xdg[0]) {
         base = xdg;
     } else {
         const char* home = std::getenv("HOME");
-        base = home ? std::string(home) + "/.config" : ".";
+        base = home ? std::filesystem::path(home) / ".config" : std::filesystem::path(".");
     }
-    return base + "/baudmine/settings.ini";
+    return (base / "baudmine" / "settings.ini").string();
 #endif
 }
 
@@ -77,19 +83,9 @@ bool Config::load(const std::string& path) {
 
 #ifndef __EMSCRIPTEN__
 static void ensureDir(const std::string& path) {
-    // Create parent directories.
-    auto lastSlash = path.rfind('/');
-    if (lastSlash == std::string::npos) return;
-    std::string dir = path.substr(0, lastSlash);
-    // Simple recursive mkdir.
-    for (size_t i = 1; i < dir.size(); ++i) {
-        if (dir[i] == '/') {
-            dir[i] = '\0';
-            mkdir(dir.c_str(), 0755);
-            dir[i] = '/';
-        }
-    }
-    mkdir(dir.c_str(), 0755);
+    std::filesystem::path p(path);
+    if (p.has_parent_path())
+        std::filesystem::create_directories(p.parent_path());
 }
 #endif
 

src/core/Types.h

@@ -15,7 +15,7 @@ namespace baudmine {
 constexpr int kMinFFTSize = 256;
 constexpr int kMaxFFTSize = 65536;
 constexpr int kDefaultFFTSize = 4096;
-constexpr int kWaterfallHistory = 2048;
+constexpr int kWaterfallHistory = 512;
 constexpr int kDefaultWindowWidth  = 1400;
 constexpr int kDefaultWindowHeight = 900;
 

src/dsp/SpectrumAnalyzer.cpp

@@ -105,7 +105,7 @@ void SpectrumAnalyzer::processBlock() {
         for (float& v : channelSpectra_[ch])
             v += windowCorrection_;
         channelWaterfalls_[ch].push_back(channelSpectra_[ch]);
-        if (channelWaterfalls_[ch].size() > kWaterfallHistory)
+        if (channelWaterfalls_[ch].size() > static_cast<size_t>(kWaterfallHistory))
             channelWaterfalls_[ch].pop_front();
     }
     newSpectrumReady_ = true;

src/ui/Application.cpp

@@ -30,6 +30,11 @@ EM_JS(void, js_clearCanvasInlineSize, (), {
     if (c) { c.style.width = ''; c.style.height = ''; }
 });
 
+#elif defined(_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+#include <GL/gl.h>
 #else
 #include <GL/gl.h>
 #endif
@@ -231,12 +236,14 @@ bool Application::init(int argc, char** argv) {
 }
 
 void Application::shutdown() {
+    if (!window_) return;  // already shut down
     audio_.closeAll();
     ImGui_ImplOpenGL3_Shutdown();
     ImGui_ImplSDL2_Shutdown();
     ImGui::DestroyContext();
     if (glContext_) { SDL_GL_DeleteContext(glContext_); glContext_ = nullptr; }
-    if (window_)    { SDL_DestroyWindow(window_); window_ = nullptr; }
+    SDL_DestroyWindow(window_);
+    window_ = nullptr;
     SDL_Quit();
 }
 
@@ -307,30 +314,65 @@ void Application::processAudio() {
         const auto& mathChannels = audio_.mathChannels();
         const auto& mathSpectra  = audio_.mathSpectra();
 
-        if (ui_.waterfallMultiCh && nSpec > 1) {
-            std::vector<std::vector<float>> wfSpectra;
-            std::vector<WaterfallChannelInfo> wfInfo;
-
-            for (int ch = 0; ch < nSpec; ++ch) {
-                const auto& c = ui_.channelColors[ch % kMaxChannels];
-                wfSpectra.push_back(audio_.getSpectrum(ch));
-                wfInfo.push_back({c.x, c.y, c.z,
-                                  ui_.channelEnabled[ch % kMaxChannels]});
-            }
-            for (size_t mi = 0; mi < mathChannels.size(); ++mi) {
-                if (mathChannels[mi].enabled && mathChannels[mi].waterfall &&
-                    mi < mathSpectra.size()) {
-                    const auto& c = mathChannels[mi].color;
-                    wfSpectra.push_back(mathSpectra[mi]);
-                    wfInfo.push_back({c[0], c[1], c[2], true});
-                }
-            }
-            waterfall_.pushLineMulti(wfSpectra, wfInfo, ui_.minDB, ui_.maxDB);
-        } else {
-            int wfCh = std::clamp(ui_.waterfallChannel, 0, nSpec - 1);
-            waterfall_.pushLine(audio_.getSpectrum(wfCh), ui_.minDB, ui_.maxDB);
-        }
+        // Push ALL new spectra to the waterfall so that the scroll rate
+        // is determined by the audio sample rate, not the display refresh.
         int curCh = std::clamp(ui_.waterfallChannel, 0, nSpec - 1);
+        const auto& traceHist = audio_.getWaterfallHistory(curCh);
+        int traceHistSz = static_cast<int>(traceHist.size());
+
+        if (ui_.waterfallMultiCh && nSpec > 1) {
+            // For multi-channel: replay the last spectraThisFrame entries
+            // from channel 0's history to get per-step data.  Other
+            // channels have the same count of new entries.
+            const auto& hist0 = audio_.getWaterfallHistory(0);
+            int histSz = static_cast<int>(hist0.size());
+            int start = std::max(0, histSz - spectraThisFrame);
+
+            for (int si = start; si < histSz; ++si) {
+                std::vector<std::vector<float>> wfSpectra;
+                std::vector<WaterfallChannelInfo> wfInfo;
+
+                for (int ch = 0; ch < nSpec; ++ch) {
+                    const auto& c = ui_.channelColors[ch % kMaxChannels];
+                    const auto& hist = audio_.getWaterfallHistory(ch);
+                    int idx = std::max(0, static_cast<int>(hist.size()) - (histSz - si));
+                    wfSpectra.push_back(hist[idx]);
+                    wfInfo.push_back({c.x, c.y, c.z,
+                                      ui_.channelEnabled[ch % kMaxChannels]});
+                }
+                // Math channels: use their own waterfall history.
+                for (size_t mi = 0; mi < mathChannels.size(); ++mi) {
+                    if (mathChannels[mi].enabled && mathChannels[mi].waterfall &&
+                        mi < mathSpectra.size()) {
+                        const auto& c = mathChannels[mi].color;
+                        const auto& mHist = audio_.mathWaterfallHistory(static_cast<int>(mi));
+                        int mHistSz = static_cast<int>(mHist.size());
+                        int mIdx = std::max(0, mHistSz - (histSz - si));
+                        if (mIdx < mHistSz) {
+                            wfSpectra.push_back(mHist[mIdx]);
+                        } else {
+                            wfSpectra.push_back(mathSpectra[mi]);
+                        }
+                        wfInfo.push_back({c[0], c[1], c[2], true});
+                    }
+                }
+                waterfall_.pushLineMulti(wfSpectra, wfInfo, ui_.minDB, ui_.maxDB);
+
+                // Push peak trace entry synchronized with each waterfall line.
+                int tIdx = std::max(0, traceHistSz - (histSz - si));
+                measurements_.pushPeakTrace(traceHist[tIdx],
+                                            settings.sampleRate, settings.isIQ, settings.fftSize);
+            }
+        } else {
+            const auto& hist = audio_.getWaterfallHistory(curCh);
+            int histSz = static_cast<int>(hist.size());
+            int start = std::max(0, histSz - spectraThisFrame);
+            for (int si = start; si < histSz; ++si) {
+                waterfall_.pushLine(hist[si], ui_.minDB, ui_.maxDB);
+                measurements_.pushPeakTrace(hist[si],
+                                            settings.sampleRate, settings.isIQ, settings.fftSize);
+            }
+        }
         cursors_.update(audio_.getSpectrum(curCh),
                        settings.sampleRate, settings.isIQ, settings.fftSize);
         measurements_.update(audio_.getSpectrum(curCh),
@@ -470,6 +512,9 @@ void Application::render() {
             ImGui::MenuItem("Additive Blend", nullptr, &specDisplay_.additiveBlend);
             if (ImGui::IsItemHovered())
                 ImGui::SetTooltip("Mix multi-channel spectrum colors additively");
+            ImGui::MenuItem("Rulers", nullptr, &displayPanel_.showRuler);
+            if (ImGui::IsItemHovered())
+                ImGui::SetTooltip("Show timescale ruler on waterfall");
             ImGui::Separator();
             if (ImGui::MenuItem("VSync", nullptr, &vsync_)) {
                 SDL_GL_SetSwapInterval(vsync_ ? 1 : 0);
@@ -674,8 +719,10 @@ void Application::loadConfig() {
     specDisplay_.peakHoldDecay    = config_.getFloat("peak_hold_decay", specDisplay_.peakHoldDecay);
     specDisplay_.additiveBlend    = config_.getBool("additive_blend", specDisplay_.additiveBlend);
     cursors_.snapToPeaks          = config_.getBool("snap_to_peaks", cursors_.snapToPeaks);
+    displayPanel_.showRuler       = config_.getBool("show_ruler", displayPanel_.showRuler);
     measurements_.traceMinFreq    = config_.getFloat("trace_min_freq", measurements_.traceMinFreq);
     measurements_.traceMaxFreq    = config_.getFloat("trace_max_freq", measurements_.traceMaxFreq);
+    ui_.specMinPixPerBin          = config_.getInt("spec_min_pix_per_bin", ui_.specMinPixPerBin);
 
     // Clamp
     controlPanel_.fftSizeIdx   = std::clamp(controlPanel_.fftSizeIdx, 0, ControlPanel::kNumFFTSizes - 1);
@@ -738,8 +785,10 @@ void Application::saveConfig() const {
     cfg.setFloat("peak_hold_decay", specDisplay_.peakHoldDecay);
     cfg.setBool("additive_blend", specDisplay_.additiveBlend);
     cfg.setBool("snap_to_peaks", cursors_.snapToPeaks);
+    cfg.setBool("show_ruler", displayPanel_.showRuler);
     cfg.setFloat("trace_min_freq", measurements_.traceMinFreq);
     cfg.setFloat("trace_max_freq", measurements_.traceMaxFreq);
+    cfg.setInt("spec_min_pix_per_bin", ui_.specMinPixPerBin);
 
     int devIdx = audio_.deviceIdx();
     if (devIdx >= 0 && devIdx < static_cast<int>(devices.size()))

src/ui/ControlPanel.cpp

@@ -95,6 +95,23 @@ void ControlPanel::render(AudioEngine& audio, UIState& ui,
             ImGui::GetWindowDrawList()->AddText({tx, ty}, IM_COL32(255, 255, 255, 220), overlayText);
             if (ImGui::IsItemHovered()) ImGui::SetTooltip("Overlap");
         }
+
+        // Overrun indicator
+        {
+            int overruns = audio.overrunCount();
+            float now = static_cast<float>(ImGui::GetTime());
+            if (overruns > lastOverrunCount_) {
+                lastOverrunCount_ = overruns;
+                lastOverrunTime_ = now;
+            }
+            if (overruns > 0 && (now - lastOverrunTime_) < 3.0f) {
+                ImGui::TextColored({1.0f, 0.4f, 0.4f, 1.0f},
+                                   "Input overrun: %d FFTs", overruns);
+            } else if (overruns > 0) {
+                audio.resetOverrunCount();
+                lastOverrunCount_ = 0;
+            }
+        }
     }
 
     // ── Display ──
@@ -178,6 +195,15 @@ void ControlPanel::render(AudioEngine& audio, UIState& ui,
             }
             if (ImGui::IsItemHovered()) ImGui::SetTooltip("Reset to 2x zoom");
         }
+
+        {
+            ImGui::AlignTextToFramePadding();
+            ImGui::Text("Decim:");
+            ImGui::SameLine();
+            ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
+            ImGui::SliderInt("##decimation", &ui.specMinPixPerBin, 1, 8, "%d px/bin");
+            if (ImGui::IsItemHovered()) ImGui::SetTooltip("Spectrum frequency decimation (peak-detect)");
+        }
     }
 
     // ── Channels ──

src/ui/ControlPanel.h

@@ -45,6 +45,10 @@ private:
     bool needsSave_   = false;
     bool needsUpdate_ = false;
 
+    // Overrun display
+    int   lastOverrunCount_ = 0;
+    float lastOverrunTime_  = 0.0f;  // ImGui time of last overrun
+
     void flagSave()   { needsSave_ = true; }
     void flagUpdate() { needsUpdate_ = true; }
 };

src/ui/DisplayPanel.cpp

@@ -5,11 +5,27 @@
 #include <algorithm>
 #include <cmath>
 #include <cstdio>
+#include <cstring>
 
 namespace baudmine {
 
 namespace {
 
+// Ruler styling constants (shared by time and dB rulers).
+constexpr ImU32 kRulerBg       = IM_COL32(20, 20, 30, 220);
+constexpr ImU32 kRulerTickCol  = IM_COL32(200, 200, 220, 230);
+constexpr ImU32 kRulerLabelCol = IM_COL32(220, 220, 240, 240);
+constexpr ImU32 kRulerUnitCol  = IM_COL32(180, 180, 200, 220);
+
+// Pick the smallest "nice" value from a sorted table that is >= target.
+// Returns the last element if none qualifies.
+template<typename T, size_t N>
+T pickNiceStep(const T (&table)[N], T target) {
+    for (const T& v : table)
+        if (v >= target) return v;
+    return table[N - 1];
+}
+
 // Zoom the view range centered on a screen-fraction cursor position.
 void zoomView(float& viewLo, float& viewHi, float cursorScreenFrac, float wheelDir) {
     float viewFrac = viewLo + cursorScreenFrac * (viewHi - viewLo);
@@ -44,11 +60,11 @@ void DisplayPanel::renderSpectrum(AudioEngine& audio, UIState& ui,
                                    Measurements& measurements) {
     const auto& settings = audio.settings();
 
-    float availW = ImGui::GetContentRegionAvail().x;
+    float availW = ImGui::GetContentRegionAvail().x - rulerWidth_;
     float specH = ImGui::GetContentRegionAvail().y;
 
     ImVec2 pos = ImGui::GetCursorScreenPos();
-    specPosX = pos.x;
+    specPosX = pos.x + rulerWidth_;
     specPosY = pos.y;
     specSizeX = availW;
     specSizeY = specH;
@@ -83,10 +99,11 @@ void DisplayPanel::renderSpectrum(AudioEngine& audio, UIState& ui,
     }
 
     specDisplay.updatePeakHold(allSpectraScratch_);
+    specDisplay.dbLabelOffsetX = rulerWidth_;
     specDisplay.draw(allSpectraScratch_, stylesScratch_, ui.minDB, ui.maxDB,
                      settings.sampleRate, settings.isIQ, ui.freqScale,
                      specPosX, specPosY, specSizeX, specSizeY,
-                     ui.viewLo, ui.viewHi);
+                     ui.viewLo, ui.viewHi, ui.specMinPixPerBin);
 
     cursors.draw(specDisplay, specPosX, specPosY, specSizeX, specSizeY,
                  settings.sampleRate, settings.isIQ, ui.freqScale, ui.minDB, ui.maxDB,
@@ -96,10 +113,45 @@ void DisplayPanel::renderSpectrum(AudioEngine& audio, UIState& ui,
                       settings.sampleRate, settings.isIQ, ui.freqScale, ui.minDB, ui.maxDB,
                       ui.viewLo, ui.viewHi);
 
+    // ── dB ruler ──
+    if (showRuler && rulerWidth_ > 0.0f) {
+        ImDrawList* dl = ImGui::GetWindowDrawList();
+        float rulerX = pos.x;
+
+        dl->AddRectFilled({rulerX, specPosY},
+                          {rulerX + rulerWidth_, specPosY + specH}, kRulerBg);
+        dl->AddLine({rulerX + rulerWidth_ - 1, specPosY},
+                    {rulerX + rulerWidth_ - 1, specPosY + specH},
+                    kRulerTickCol, 1.0f);
+
+        constexpr float kTargetDbSpacing = 30.0f;
+        float dbRange = ui.maxDB - ui.minDB;
+        static const float kNiceDbSteps[] = {1.0f, 2.0f, 5.0f, 10.0f, 20.0f, 50.0f, 100.0f};
+        float dbStep = pickNiceStep(kNiceDbSteps, dbRange * (kTargetDbSpacing / specH));
+
+        float charH = ImGui::CalcTextSize("0").y;
+        float bottomCutoff = specPosY + specH - charH * 2 - 4.0f;
+        for (float db = std::ceil(ui.minDB / dbStep) * dbStep; db <= ui.maxDB + 0.01f; db += dbStep) {
+            float y = specPosY + specH * (1.0f - (db - ui.minDB) / dbRange);
+            if (y > bottomCutoff) continue;
+
+            dl->AddLine({rulerX, y},
+                        {rulerX + rulerWidth_ - 1, y}, kRulerTickCol, 2.0f);
+
+            char numBuf[16];
+            std::snprintf(numBuf, sizeof(numBuf), "%.0f", db);
+            dl->AddText({rulerX - 3.0f, y + 2.0f}, kRulerLabelCol, numBuf);
+        }
+
+        ImVec2 unitSz = ImGui::CalcTextSize("dB");
+        dl->AddText({rulerX + 2.0f, specPosY + specH - unitSz.y - 2.0f},
+                    kRulerUnitCol, "dB");
+    }
+
     handleSpectrumInput(audio, ui, specDisplay, cursors,
                         specPosX, specPosY, specSizeX, specSizeY);
 
-    ImGui::Dummy({availW, specH});
+    ImGui::Dummy({availW + rulerWidth_, specH});
 }
 
 void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
@@ -108,11 +160,16 @@ void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
                                     ColorMap& colorMap) {
     const auto& settings = audio.settings();
 
-    float availW = ImGui::GetContentRegionAvail().x;
+    float fullW = ImGui::GetContentRegionAvail().x;
     constexpr float kSplitterH = 6.0f;
     float parentH = ImGui::GetContentRegionAvail().y;
     float availH = (parentH - kSplitterH) * (1.0f - spectrumFrac);
 
+    // Compute ruler width (used by both waterfall and spectrum rendering).
+    float labelW = ImGui::CalcTextSize("-000").x;
+    rulerWidth_ = showRuler ? labelW : 0.0f;
+    float availW = fullW - rulerWidth_;
+
     int neededH = std::max(1024, static_cast<int>(availH) + 1);
     int binCount = std::max(1, audio.spectrumSize());
     if (binCount != waterfall.width() || waterfall.height() < neededH) {
@@ -121,7 +178,8 @@ void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
     }
 
     if (waterfall.textureID()) {
-        ImVec2 pos = ImGui::GetCursorScreenPos();
+        ImVec2 basePos = ImGui::GetCursorScreenPos();
+        ImVec2 pos = {basePos.x + rulerWidth_, basePos.y};
         ImDrawList* dl = ImGui::GetWindowDrawList();
         auto texID = static_cast<ImTextureID>(waterfall.textureID());
 
@@ -213,10 +271,86 @@ void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
 
         wfPosX = pos.x; wfPosY = pos.y; wfSizeX = availW; wfSizeY = availH;
 
+        int hopSamples = std::max(1, static_cast<int>(settings.fftSize * (1.0f - settings.overlap)));
+        double secondsPerLine = static_cast<double>(hopSamples) / settings.sampleRate;
+
         measurements.drawWaterfall(specDisplay, wfPosX, wfPosY, wfSizeX, wfSizeY,
                                    settings.sampleRate, settings.isIQ, ui.freqScale,
                                    ui.viewLo, ui.viewHi, screenRows, audio.spectrumSize());
 
+        // ── Timescale ruler ──
+        if (showRuler && rulerWidth_ > 0.0f) {
+            double totalTime = screenRows * secondsPerLine;
+
+            float rulerX = basePos.x;
+            float rulerY = basePos.y;
+
+            dl->AddRectFilled({rulerX, rulerY},
+                              {rulerX + rulerWidth_, rulerY + availH}, kRulerBg);
+            dl->AddLine({rulerX + rulerWidth_ - 1, rulerY},
+                        {rulerX + rulerWidth_ - 1, rulerY + availH},
+                        kRulerTickCol, 1.0f);
+
+            // Pick a nice major tick interval targeting ~80px spacing.
+            constexpr float kTargetTickSpacing = 80.0f;
+            static const double kNiceIntervals[] = {
+                0.001, 0.002, 0.005, 0.01, 0.02, 0.05,
+                0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, 20.0, 30.0, 60.0, 120.0, 300.0
+            };
+            double majorInterval = pickNiceStep(kNiceIntervals,
+                                                totalTime * (kTargetTickSpacing / availH));
+            double minorInterval = majorInterval / 4.0;
+            bool useMs = (majorInterval < 1.0);
+            float charH = ImGui::CalcTextSize("0").y;
+
+            // Minor ticks
+            float minorTickLen = rulerWidth_ / 3.0f;
+            for (int idx = 1;; ++idx) {
+                double t = minorInterval * idx;
+                if (t >= totalTime) break;
+                if (idx % 4 == 0) continue;
+
+                float y = rulerY + availH - static_cast<float>(t / totalTime) * availH;
+                if (y < rulerY) break;
+
+                float tickLen = (idx % 2 == 0) ? minorTickLen * 1.5f : minorTickLen;
+                dl->AddLine({rulerX + rulerWidth_ - 1 - tickLen, y},
+                            {rulerX + rulerWidth_ - 1, y}, kRulerTickCol, 1.5f);
+            }
+
+            // Major ticks with vertically stacked digit labels
+            for (int idx = 1;; ++idx) {
+                double t = majorInterval * idx;
+                if (t >= totalTime) break;
+
+                float y = rulerY + availH - static_cast<float>(t / totalTime) * availH;
+                if (y < rulerY) break;
+
+                dl->AddLine({rulerX, y},
+                            {rulerX + rulerWidth_ - 1, y}, kRulerTickCol, 2.0f);
+
+                char numBuf[16];
+                int ival = static_cast<int>((useMs ? t * 1000.0 : t) + 0.5);
+                std::snprintf(numBuf, sizeof(numBuf), "%d", ival);
+
+                int nDigits = static_cast<int>(std::strlen(numBuf));
+                float digitX = rulerX + 2.0f;
+                float digitY = y + 3.0f;
+                for (int d = 0; d < nDigits; ++d) {
+                    if (digitY + charH > rulerY + availH - charH) break;
+                    char ch[2] = {numBuf[d], '\0'};
+                    dl->AddText({digitX, digitY}, kRulerLabelCol, ch);
+                    digitY += charH;
+                }
+            }
+
+            // Unit label at the very bottom
+            const char* unit = useMs ? "ms" : "s";
+            ImVec2 unitSz = ImGui::CalcTextSize(unit);
+            dl->AddText({rulerX + 2.0f, rulerY + availH - unitSz.y - 2.0f},
+                        kRulerUnitCol, unit);
+        }
+
         // ── Mouse interaction: zoom, pan & hover on waterfall ──
         ImGuiIO& io = ImGui::GetIO();
         float mx = io.MousePos.x;
@@ -237,9 +371,6 @@ void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
             bin = std::clamp(bin, 0, bins - 1);
 
             float yFrac = 1.0f - (my - pos.y) / availH;
-            int hopSamples = static_cast<int>(settings.fftSize * (1.0f - settings.overlap));
-            if (hopSamples < 1) hopSamples = 1;
-            double secondsPerLine = static_cast<double>(hopSamples) / settings.sampleRate;
             hoverWfTimeOff = static_cast<float>(yFrac * screenRows * secondsPerLine);
 
             int curCh = std::clamp(ui.waterfallChannel, 0, audio.totalNumSpectra() - 1);
@@ -247,9 +378,7 @@ void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
             if (!spec.empty()) {
                 cursors.hover = {true, freq, spec[bin], bin};
             }
-        }
 
-        if (inWaterfall) {
             if (io.MouseWheel != 0)
                 zoomView(ui.viewLo, ui.viewHi, (mx - pos.x) / availW, io.MouseWheel);
 
@@ -263,7 +392,7 @@ void DisplayPanel::renderWaterfall(AudioEngine& audio, UIState& ui,
         }
     }
 
-    ImGui::Dummy({availW, availH});
+    ImGui::Dummy({fullW, availH});
 }
 
 void DisplayPanel::renderHoverOverlay(const AudioEngine& audio, const UIState& ui,

src/ui/DisplayPanel.h

@@ -41,6 +41,8 @@ public:
 
     float spectrumFrac  = 0.35f;
     bool  draggingSplit  = false;
+    bool  showRuler      = false;
+    float rulerWidth_    = 0.0f;   // current ruler width in pixels (0 when hidden)
 
 private:
     void handleSpectrumInput(AudioEngine& audio, UIState& ui,

src/ui/Measurements.cpp

@@ -61,6 +61,38 @@ void Measurements::findPeaks(const std::vector<float>& spectrumDB, int maxN,
     }
 }
 
+void Measurements::pushPeakTrace(const std::vector<float>& spectrumDB,
+                                  double sampleRate, bool isIQ, int fftSize) {
+    if (spectrumDB.empty()) return;
+
+    constexpr int kMaxHistory = 4096;
+    if (static_cast<int>(peakHistBins_.size()) < kMaxHistory)
+        peakHistBins_.resize(kMaxHistory, -1);
+
+    auto it = std::max_element(spectrumDB.begin(), spectrumDB.end());
+    int traceBin = static_cast<int>(std::distance(spectrumDB.begin(), it));
+
+    // Optionally restrict to a frequency range.
+    int bins = static_cast<int>(spectrumDB.size());
+    if (traceMinFreq > 0.0f || traceMaxFreq > 0.0f) {
+        double fMin = isIQ ? -sampleRate / 2.0 : 0.0;
+        double fMax = isIQ ?  sampleRate / 2.0 : sampleRate / 2.0;
+        int loB = 0, hiB = bins - 1;
+        if (traceMinFreq > 0.0f)
+            loB = std::max(0, static_cast<int>((traceMinFreq - fMin) / (fMax - fMin) * bins));
+        if (traceMaxFreq > 0.0f)
+            hiB = std::min(bins - 1, static_cast<int>((traceMaxFreq - fMin) / (fMax - fMin) * bins));
+        if (loB <= hiB) {
+            auto rangeIt = std::max_element(spectrumDB.begin() + loB, spectrumDB.begin() + hiB + 1);
+            traceBin = static_cast<int>(std::distance(spectrumDB.begin(), rangeIt));
+        }
+    }
+
+    peakHistIdx_ = (peakHistIdx_ + 1) % kMaxHistory;
+    peakHistBins_[peakHistIdx_] = traceBin;
+    if (peakHistLen_ < kMaxHistory) ++peakHistLen_;
+}
+
 void Measurements::update(const std::vector<float>& spectrumDB,
                            double sampleRate, bool isIQ, int fftSize) {
     lastSampleRate_ = sampleRate;
@@ -71,32 +103,6 @@ void Measurements::update(const std::vector<float>& spectrumDB,
         globalPeak_.bin = bin;
         globalPeak_.dB = *it;
         globalPeak_.freq = binToFreq(bin, sampleRate, isIQ, fftSize);
-
-        // Push into peak history circular buffer (with optional freq range filter)
-        constexpr int kMaxHistory = 4096;
-        if (static_cast<int>(peakHistBins_.size()) < kMaxHistory)
-            peakHistBins_.resize(kMaxHistory, -1);
-
-        // Find peak within the trace frequency range
-        int traceBin = bin;
-        int bins = static_cast<int>(spectrumDB.size());
-        if (traceMinFreq > 0.0f || traceMaxFreq > 0.0f) {
-            double fMin = isIQ ? -sampleRate / 2.0 : 0.0;
-            double fMax = isIQ ?  sampleRate / 2.0 : sampleRate / 2.0;
-            int loB = 0, hiB = bins - 1;
-            if (traceMinFreq > 0.0f)
-                loB = std::max(0, static_cast<int>((traceMinFreq - fMin) / (fMax - fMin) * bins));
-            if (traceMaxFreq > 0.0f)
-                hiB = std::min(bins - 1, static_cast<int>((traceMaxFreq - fMin) / (fMax - fMin) * bins));
-            if (loB <= hiB) {
-                auto rangeIt = std::max_element(spectrumDB.begin() + loB, spectrumDB.begin() + hiB + 1);
-                traceBin = static_cast<int>(std::distance(spectrumDB.begin(), rangeIt));
-            }
-        }
-
-        peakHistIdx_ = (peakHistIdx_ + 1) % kMaxHistory;
-        peakHistBins_[peakHistIdx_] = traceBin;
-        if (peakHistLen_ < kMaxHistory) ++peakHistLen_;
     }
 
     if (!enabled) { peaks_.clear(); return; }

src/ui/Measurements.h

@@ -18,6 +18,10 @@ public:
     void update(const std::vector<float>& spectrumDB,
                 double sampleRate, bool isIQ, int fftSize);
 
+    // Push a single peak trace entry for this spectrum (call once per waterfall line).
+    void pushPeakTrace(const std::vector<float>& spectrumDB,
+                       double sampleRate, bool isIQ, int fftSize);
+
     // Draw markers on the spectrum display area.
     void draw(const SpectrumDisplay& specDisplay,
               float posX, float posY, float sizeX, float sizeY,

src/ui/SpectrumDisplay.cpp

@@ -4,6 +4,11 @@
 
 #ifdef __EMSCRIPTEN__
 #include <GLES2/gl2.h>
+#elif defined(_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+#include <GL/gl.h>
 #else
 #include <GL/gl.h>
 #endif
@@ -55,9 +60,11 @@ static void buildPolyline(const std::vector<float>& spectrumDB,
                            bool isIQ, FreqScale freqScale,
                            float posX, float posY, float sizeX, float sizeY,
                            float viewLo, float viewHi,
-                           std::vector<ImVec2>& outPoints) {
+                           std::vector<ImVec2>& outPoints,
+                           int minPixPerBin = 1) {
     int bins = static_cast<int>(spectrumDB.size());
-    int displayPts = std::min(bins, static_cast<int>(sizeX));
+    int maxPts = std::max(1, static_cast<int>(sizeX) / std::max(1, minPixPerBin));
+    int displayPts = std::min(bins, maxPts);
     if (displayPts < 2) displayPts = 2;
 
     outPoints.resize(displayPts);
@@ -103,7 +110,8 @@ void SpectrumDisplay::draw(const std::vector<std::vector<float>>& spectra,
                            FreqScale freqScale,
                            float posX, float posY,
                            float sizeX, float sizeY,
-                           float viewLo, float viewHi) const {
+                           float viewLo, float viewHi,
+                           int minPixPerBin) const {
     if (spectra.empty() || spectra[0].empty() || sizeX <= 0 || sizeY <= 0) return;
 
     ImDrawList* dl = ImGui::GetWindowDrawList();
@@ -141,7 +149,7 @@ void SpectrumDisplay::draw(const std::vector<std::vector<float>>& spectra,
             dl->AddLine({posX, y}, {posX + sizeX, y}, gridCol);
             char label[16];
             std::snprintf(label, sizeof(label), "%.0f", db);
-            dl->AddText({posX + 2, y - ImGui::GetTextLineHeight()}, textCol, label);
+            dl->AddText({posX + 2 - dbLabelOffsetX, y - ImGui::GetTextLineHeight()}, textCol, label);
         }
 
         // ── Vertical (frequency) grid — adapt count to available width ──
@@ -173,7 +181,7 @@ void SpectrumDisplay::draw(const std::vector<std::vector<float>>& spectra,
         if (spectra[ch].empty()) continue;
         buildPolyline(spectra[ch], minDB, maxDB,
                       isIQ, freqScale, posX, posY, sizeX, sizeY,
-                      viewLo, viewHi, allPoints[ch]);
+                      viewLo, viewHi, allPoints[ch], minPixPerBin);
     }
 
     // Draw spectra: all fills first, then all lines on top.
@@ -232,7 +240,7 @@ void SpectrumDisplay::draw(const std::vector<std::vector<float>>& spectra,
             ImU32 col = (st.lineColor & 0x00FFFFFF) | 0x90000000;
             buildPolyline(peakHold_[ch], minDB, maxDB,
                           isIQ, freqScale, posX, posY, sizeX, sizeY,
-                          viewLo, viewHi, phPoints);
+                          viewLo, viewHi, phPoints, minPixPerBin);
             if (phPoints.size() >= 2)
                 dl->AddPolyline(phPoints.data(), static_cast<int>(phPoints.size()),
                                 col, ImDrawFlags_None, 1.0f);

src/ui/SpectrumDisplay.h

@@ -22,7 +22,8 @@ public:
               double sampleRate, bool isIQ,
               FreqScale freqScale,
               float posX, float posY, float sizeX, float sizeY,
-              float viewLo = 0.0f, float viewHi = 1.0f) const;
+              float viewLo = 0.0f, float viewHi = 1.0f,
+              int minPixPerBin = 1) const;
 
     // Convenience: single-channel draw (backward compat).
     void draw(const std::vector<float>& spectrumDB,
@@ -49,6 +50,7 @@ public:
     bool  additiveBlend  = true;   // additive color mixing for multi-channel
     bool  peakHoldEnable = false;
     float peakHoldDecay  = 20.0f;  // dB/second decay rate
+    float dbLabelOffsetX = 0.0f;   // shift dB labels left (into ruler area)
 
 private:
     // One peak-hold trace per channel.

src/ui/UIState.h

@@ -17,6 +17,7 @@ struct UIState {
 
     int  waterfallChannel = 0;
     bool waterfallMultiCh = true;
+    int  specMinPixPerBin = 1;   // min screen pixels per spectrum bin (1 = no decimation)
     std::array<bool, kMaxChannels> channelEnabled = {true,true,true,true,true,true,true,true};
     // Complementary pairs: colors at indices 0+1, 2+3, 4+5, 6+7 sum to white.
     std::array<ImVec4, kMaxChannels> channelColors = {{

src/ui/WaterfallDisplay.h

@@ -2,7 +2,15 @@
 
 #include "core/Types.h"
 #include "ui/ColorMap.h"
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+#endif
 #include <GL/gl.h>
+#ifndef GL_CLAMP_TO_EDGE // for Windows
+#define GL_CLAMP_TO_EDGE 0x812F
+#endif
 #include <vector>
 #include <deque>