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Merged
acolombier merged 3 commits into from
Jan 27, 2026
Merged

Implement Stem VU Meter Control Objects #15887

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aaf0efe
Implement Stem VU Meter Control Objects
xARSENICx Jan 20, 2026
423e8b1
test(stem): Fix VU Meter unit test assertions and robustness for mute…
xARSENICx Jan 25, 2026
6bcba83
refactor(engine): Optional legacy CO aliases for EngineVuMeter
xARSENICx Jan 27, 2026
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14 changes: 13 additions & 1 deletion src/engine/channels/enginedeck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@ EngineDeck::EngineDeck(

m_stemGain.reserve(mixxx::kMaxSupportedStems);
m_stemMute.reserve(mixxx::kMaxSupportedStems);
m_stemVuMeter.reserve(mixxx::kMaxSupportedStems);
for (int stemIdx = 0; stemIdx < mixxx::kMaxSupportedStems; stemIdx++) {
m_stemGain.emplace_back(std::make_unique<ControlPotmeter>(
ConfigKey(getGroupForStem(getGroup(), stemIdx), QStringLiteral("volume"))));
Expand All @@ -80,6 +81,9 @@ EngineDeck::EngineDeck(
ConfigKey(getGroupForStem(getGroup(), stemIdx), QStringLiteral("mute")));
pMuteButton->setButtonMode(mixxx::control::ButtonMode::PowerWindow);
m_stemMute.push_back(std::move(pMuteButton));

m_stemVuMeter.emplace_back(std::make_unique<EngineVuMeter>(
getGroupForStem(getGroup(), stemIdx), QString(), false));
}
#endif
}
Expand Down Expand Up @@ -126,7 +130,8 @@ void EngineDeck::addStemHandle(const ChannelHandleAndGroup& stemHandleGroup) {
void EngineDeck::processStem(CSAMPLE* pOut, const std::size_t bufferSize) {
mixxx::audio::ChannelCount chCount = m_pBuffer->getChannelCount();
VERIFY_OR_DEBUG_ASSERT(m_stems.size() <= chCount &&
m_stemMute.size() <= chCount && m_stemGain.size() <= chCount) {
m_stemMute.size() <= chCount && m_stemGain.size() <= chCount &&
m_stemVuMeter.size() <= chCount) {
return;
};
mixxx::audio::SampleRate sampleRate = mixxx::audio::SampleRate::fromDouble(m_sampleRate.get());
Expand Down Expand Up @@ -184,6 +189,8 @@ void EngineDeck::processStem(CSAMPLE* pOut, const std::size_t bufferSize) {
// gain) gain changes will yield to audio cracks.
m_stemsGainCache[stemIdx] = stemGain;

m_stemVuMeter[stemIdx]->process(pOut, bufferSize);
Comment thread
JoergAtGithub marked this conversation as resolved.

// Put back the stem frames into the steam buffer (LRLR -> LR......LR......)
SampleUtil::insertStereoToMulti(
pIn,
Expand Down Expand Up @@ -299,6 +306,11 @@ EngineChannel::ActiveState EngineDeck::updateActiveState() {
}
if (m_active) {
m_vuMeter.reset();
#ifdef __STEM__
for (auto& stemVuMeter : m_stemVuMeter) {
stemVuMeter->reset();
}
#endif
m_active = false;
return ActiveState::WasActive;
}
Expand Down
1 change: 1 addition & 0 deletions src/engine/channels/enginedeck.h
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,7 @@ class EngineDeck : public EngineChannel, public AudioDestination {
std::unique_ptr<ControlObject> m_pStemCount;
std::vector<std::unique_ptr<ControlPotmeter>> m_stemGain;
std::vector<std::unique_ptr<ControlPushButton>> m_stemMute;
std::vector<std::unique_ptr<EngineVuMeter>> m_stemVuMeter;
bool m_stemClonedState;
#endif

Expand Down
35 changes: 20 additions & 15 deletions src/engine/enginevumeter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ namespace {

// Rate at which the vumeter is updated (using a sample rate of 44100 Hz):
constexpr unsigned int kVuUpdateRate = 30; // in Hz (1/s), fits to display frame rate
constexpr int kPeakDuration = 500; // in ms
constexpr int kPeakDuration = 500; // in ms

// Smoothing Factors
// Must be from 0-1 the lower the factor, the more smoothing that is applied
Expand All @@ -17,21 +17,27 @@ constexpr CSAMPLE kDecaySmoothing = 0.1f; //.16//.4

} // namespace

EngineVuMeter::EngineVuMeter(const QString& group, const QString& legacyGroup)
EngineVuMeter::EngineVuMeter(const QString& group,
const QString& legacyGroup,
bool createLegacyAliases)
: m_vuMeter(ConfigKey(group, QStringLiteral("vu_meter"))),
m_vuMeterLeft(ConfigKey(group, QStringLiteral("vu_meter_left"))),
m_vuMeterRight(ConfigKey(group, QStringLiteral("vu_meter_right"))),
m_peakIndicator(ConfigKey(group, QStringLiteral("peak_indicator"))),
m_peakIndicatorLeft(ConfigKey(group, QStringLiteral("peak_indicator_left"))),
m_peakIndicatorRight(ConfigKey(group, QStringLiteral("peak_indicator_right"))),
m_peakIndicatorLeft(
ConfigKey(group, QStringLiteral("peak_indicator_left"))),
m_peakIndicatorRight(
ConfigKey(group, QStringLiteral("peak_indicator_right"))),
m_sampleRate(QStringLiteral("[App]"), QStringLiteral("samplerate")) {
const QString& aliasGroup = legacyGroup.isEmpty() ? group : legacyGroup;
m_vuMeter.addAlias(ConfigKey(aliasGroup, QStringLiteral("VuMeter")));
m_vuMeterLeft.addAlias(ConfigKey(aliasGroup, QStringLiteral("VuMeterL")));
m_vuMeterRight.addAlias(ConfigKey(aliasGroup, QStringLiteral("VuMeterR")));
m_peakIndicator.addAlias(ConfigKey(aliasGroup, QStringLiteral("PeakIndicator")));
m_peakIndicatorLeft.addAlias(ConfigKey(aliasGroup, QStringLiteral("PeakIndicatorL")));
m_peakIndicatorRight.addAlias(ConfigKey(aliasGroup, QStringLiteral("PeakIndicatorR")));
if (createLegacyAliases) {
const QString& aliasGroup = legacyGroup.isEmpty() ? group : legacyGroup;
m_vuMeter.addAlias(ConfigKey(aliasGroup, QStringLiteral("VuMeter")));
m_vuMeterLeft.addAlias(ConfigKey(aliasGroup, QStringLiteral("VuMeterL")));
m_vuMeterRight.addAlias(ConfigKey(aliasGroup, QStringLiteral("VuMeterR")));
m_peakIndicator.addAlias(ConfigKey(aliasGroup, QStringLiteral("PeakIndicator")));
m_peakIndicatorLeft.addAlias(ConfigKey(aliasGroup, QStringLiteral("PeakIndicatorL")));
m_peakIndicatorRight.addAlias(ConfigKey(aliasGroup, QStringLiteral("PeakIndicatorR")));
}
// Initialize the calculation:
reset();
}
Expand Down Expand Up @@ -105,18 +111,17 @@ void EngineVuMeter::process(CSAMPLE* pIn, const std::size_t bufferSize) {
: 0.0);
}

void EngineVuMeter::doSmooth(CSAMPLE &currentVolume, CSAMPLE newVolume)
{
void EngineVuMeter::doSmooth(CSAMPLE& currentVolume, CSAMPLE newVolume) {
if (currentVolume > newVolume) {
currentVolume -= kDecaySmoothing * (currentVolume - newVolume);
} else {
currentVolume += kAttackSmoothing * (newVolume - currentVolume);
}
if (currentVolume < 0) {
currentVolume=0;
currentVolume = 0;
}
if (currentVolume > 1.0) {
currentVolume=1.0;
currentVolume = 1.0;
}
}

Expand Down
6 changes: 4 additions & 2 deletions src/engine/enginevumeter.h
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Original file line number Diff line number Diff line change
Expand Up @@ -7,14 +7,16 @@
class EngineVuMeter : public EngineObject {
Q_OBJECT
public:
EngineVuMeter(const QString& group, const QString& legacyGroup = QString());
EngineVuMeter(const QString& group,
const QString& legacyGroup = QString(),
bool createLegacyAliases = true);

virtual void process(CSAMPLE* pInOut, const std::size_t bufferSize);

void reset();

private:
void doSmooth(CSAMPLE &currentVolume, CSAMPLE newVolume);
void doSmooth(CSAMPLE& currentVolume, CSAMPLE newVolume);

ControlObject m_vuMeter;
ControlObject m_vuMeterLeft;
Expand Down
47 changes: 47 additions & 0 deletions src/test/stemcontrolobjecttest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,15 @@ class StemControlFixture : public BaseSignalPathTest,
m_pStem3FXEnabled->set(0.0);
m_pStem4FXEnabled->set(0.0);

m_pStem1VuMeter = std::make_unique<PollingControlProxy>(
getGroupForStem(m_sGroup1, 1), "vu_meter");
m_pStem2VuMeter = std::make_unique<PollingControlProxy>(
getGroupForStem(m_sGroup1, 2), "vu_meter");
m_pStem3VuMeter = std::make_unique<PollingControlProxy>(
getGroupForStem(m_sGroup1, 3), "vu_meter");
m_pStem4VuMeter = std::make_unique<PollingControlProxy>(
getGroupForStem(m_sGroup1, 4), "vu_meter");

m_pStemCount = std::make_unique<PollingControlProxy>(m_sGroup1, "stem_count");
}

Expand Down Expand Up @@ -151,6 +160,10 @@ class StemControlFixture : public BaseSignalPathTest,
std::unique_ptr<PollingControlProxy> m_pStem2FXEnabled;
std::unique_ptr<PollingControlProxy> m_pStem3FXEnabled;
std::unique_ptr<PollingControlProxy> m_pStem4FXEnabled;
std::unique_ptr<PollingControlProxy> m_pStem1VuMeter;
std::unique_ptr<PollingControlProxy> m_pStem2VuMeter;
std::unique_ptr<PollingControlProxy> m_pStem3VuMeter;
std::unique_ptr<PollingControlProxy> m_pStem4VuMeter;
std::unique_ptr<PollingControlProxy> m_pStemCount;
};

Expand Down Expand Up @@ -329,6 +342,40 @@ TEST_P(StemControlFixture, Mute) {
QStringLiteral("StemMuteControlFull"));
}

TEST_P(StemControlFixture, VuMeter) {
m_pChannel1->getEngineBuffer()->queueNewPlaypos(
mixxx::audio::FramePos{0}, EngineBuffer::SEEK_STANDARD);
m_pPlay->set(1.0);

// Initial check: silence
EXPECT_EQ(m_pStem1VuMeter->get(), 0.0);

// Process buffer to play sound
// Run enough cycles to trigger VU meter update (30Hz update rate vs ~44kHz/buffer)
for (int i = 0; i < 50; ++i) {
m_pEngineMixer->process(kProcessBufferSize);
}

// Check if VU meters picked up the signal
EXPECT_GT(m_pStem1VuMeter->get(), 0.0);
EXPECT_GT(m_pStem2VuMeter->get(), 0.0);

// Mute Stem 1
m_pStem1Mute->set(1.0);

// Process enough buffers to allow VU meter to decay to 0
// Decay is exponential, so it takes time.
for (int i = 0; i < 600; ++i) {
m_pEngineMixer->process(kProcessBufferSize);
}

// VU Meter should be near zero (allow small epsilon for imperfect decay)
EXPECT_NEAR(m_pStem1VuMeter->get(), 0.0, 0.001);

// Stem 2 should still be playing
EXPECT_GT(m_pStem2VuMeter->get(), 0.0);
}

INSTANTIATE_TEST_SUITE_P(
StemControlTest,
StemControlFixture,
Expand Down