Add stereo and bass enhance APIs via PEQ overlay.

Expose POST /api/audio/stereo-enhance and bass-enhance with 0–100 levels,
persist enhancements in AudioProfile, and document the virtual EQ mapping in
the manual and SigmaStudio chapter.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/core/test/CMakeLists.txt

@@ -29,6 +29,9 @@ add_library(digiradio_core STATIC
     "${CORE_SRC_DIR}/BiquadDesign.cpp"
     "${CORE_SRC_DIR}/MixerState.cpp"
     "${CORE_SRC_DIR}/EqProfile.cpp"
+    "${CORE_SRC_DIR}/EnhanceLevel.cpp"
+    "${CORE_SRC_DIR}/AudioEnhancements.cpp"
+    "${CORE_SRC_DIR}/EnhancementsDesign.cpp"
     "${CORE_SRC_DIR}/AudioProfile.cpp"
     "${CORE_SRC_DIR}/AudioProfileJson.cpp"
 )
@@ -63,3 +66,7 @@ add_test(NAME biquad_design_test COMMAND biquad_design_test)
 add_executable(audio_profile_json_test audio_profile_json_test.cpp)
 target_link_libraries(audio_profile_json_test PRIVATE digiradio_core)
 add_test(NAME audio_profile_json_test COMMAND audio_profile_json_test)
+
+add_executable(enhancements_design_test enhancements_design_test.cpp)
+target_link_libraries(enhancements_design_test PRIVATE digiradio_core)
+add_test(NAME enhancements_design_test COMMAND enhancements_design_test)

Software/components/core/test/audio_profile_json_test.cpp

@@ -13,6 +13,7 @@
 
 #include "core/AudioProfile.hpp"
 #include "core/AudioProfileJson.hpp"
+#include "core/EnhanceLevel.hpp"
 #include "core/EqBandIndex.hpp"
 #include "core/FrequencyHz.hpp"
 #include "core/GainDb.hpp"
@@ -52,6 +53,22 @@ namespace {
         std::cerr << "round-trip mismatch\n";
         return EXIT_FAILURE;
     }
+
+    if (parsed->enhancements.stereo.value() != 0U
+        || parsed->enhancements.bass.value() != 0U) {
+        std::cerr << "default enhancements mismatch\n";
+        return EXIT_FAILURE;
+    }
+
+    profile.enhancements.stereo = *core::EnhanceLevel::tryFromLevel(40U);
+    profile.enhancements.bass = *core::EnhanceLevel::tryFromLevel(75U);
+    const std::string json2 = core::serializeAudioProfileJson(profile);
+    const auto parsed2 = core::parseAudioProfileJson(json2);
+    if (!parsed2 || parsed2->enhancements.stereo.value() != 40U
+        || parsed2->enhancements.bass.value() != 75U) {
+        std::cerr << "enhancements round-trip mismatch\n";
+        return EXIT_FAILURE;
+    }
     return EXIT_SUCCESS;
 }
 

Software/components/core/test/enhancements_design_test.cpp

@@ -0,0 +1,124 @@
+/**
+ * @file    enhancements_design_test.cpp
+ * @brief   Host tests for enhancement-to-EQ mapping.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * @author  Michele Bigi
+ * @date    2026-07-06
+ */
+
+#include "core/AudioEnhancements.hpp"
+#include "core/EnhanceLevel.hpp"
+#include "core/EnhancementsDesign.hpp"
+#include "core/EqBandIndex.hpp"
+#include "core/EqProfile.hpp"
+
+#include <cmath>
+#include <cstdlib>
+#include <iostream>
+
+namespace {
+
+[[nodiscard]] bool nearlyEqual(float a, float b) noexcept
+{
+    return std::fabs(a - b) < 0.01F;
+}
+
+[[nodiscard]] int runBassMappingTest()
+{
+    const auto level = core::EnhanceLevel::tryFromLevel(100U);
+    if (!level) {
+        std::cerr << "level setup failed\n";
+        return EXIT_FAILURE;
+    }
+
+    core::AudioEnhancements enhancements = core::AudioEnhancements::factoryDefault();
+    enhancements.bass = *level;
+
+    const core::EqProfile base = core::EqProfile::factoryDefault();
+    const core::EqProfile effective =
+        core::applyEnhancementsToEq(base, enhancements);
+
+    const auto band1 = core::EqBandIndex::tryFromIndex(1U);
+    const auto band2 = core::EqBandIndex::tryFromIndex(2U);
+    if (!band1 || !band2) {
+        return EXIT_FAILURE;
+    }
+
+    if (!nearlyEqual(effective.band(*band1).gain.value(), 9.0F)
+        || !nearlyEqual(effective.band(*band2).gain.value(), 3.0F)) {
+        std::cerr << "bass mapping mismatch\n";
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}
+
+[[nodiscard]] int runStereoMappingTest()
+{
+    const auto level = core::EnhanceLevel::tryFromLevel(50U);
+    if (!level) {
+        std::cerr << "level setup failed\n";
+        return EXIT_FAILURE;
+    }
+
+    core::AudioEnhancements enhancements = core::AudioEnhancements::factoryDefault();
+    enhancements.stereo = *level;
+
+    const core::EqProfile base = core::EqProfile::factoryDefault();
+    const core::EqProfile effective =
+        core::applyEnhancementsToEq(base, enhancements);
+
+    const auto band3 = core::EqBandIndex::tryFromIndex(3U);
+    const auto band4 = core::EqBandIndex::tryFromIndex(4U);
+    const auto band5 = core::EqBandIndex::tryFromIndex(5U);
+    if (!band3 || !band4 || !band5) {
+        return EXIT_FAILURE;
+    }
+
+    if (!nearlyEqual(effective.band(*band3).gain.value(), -0.75F)
+        || !nearlyEqual(effective.band(*band4).gain.value(), 1.0F)
+        || !nearlyEqual(effective.band(*band5).gain.value(), 2.0F)) {
+        std::cerr << "stereo mapping mismatch\n";
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}
+
+[[nodiscard]] int runOffLeavesBaseTest()
+{
+    const core::EqProfile base = core::EqProfile::factoryDefault();
+    const core::AudioEnhancements off = core::AudioEnhancements::factoryDefault();
+    const core::EqProfile effective = core::applyEnhancementsToEq(base, off);
+
+    const auto band1 = core::EqBandIndex::tryFromIndex(1U);
+    if (!band1) {
+        return EXIT_FAILURE;
+    }
+
+    if (!nearlyEqual(effective.band(*band1).gain.value(),
+                     base.band(*band1).gain.value())) {
+        std::cerr << "off should leave base unchanged\n";
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}
+
+} // namespace
+
+int main()
+{
+    if (runBassMappingTest() != EXIT_SUCCESS) {
+        return EXIT_FAILURE;
+    }
+    if (runStereoMappingTest() != EXIT_SUCCESS) {
+        return EXIT_FAILURE;
+    }
+    if (runOffLeavesBaseTest() != EXIT_SUCCESS) {
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}