silence.cpp.hpp

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#include "fl/audio/detector/silence.h"
#include "fl/audio/audio_context.h"
#include "fl/math/math.h"
#include "fl/stl/noexcept.h"
 
namespace fl {
namespace audio {
namespace detector {
 
Silence::Silence()
    FL_NO_EXCEPT : mIsSilent(false)
    , mPreviousSilent(false)
    , mCurrentRMS(0.0f)
    , mSilenceThreshold(DEFAULT_SILENCE_THRESHOLD)
    , mHysteresis(DEFAULT_HYSTERESIS)
    , mSilenceStartTime(0)
    , mSilenceEndTime(0)
    , mMinSilenceDuration(DEFAULT_MIN_SILENCE_MS)
    , mMaxSilenceDuration(DEFAULT_MAX_SILENCE_MS)
    , mLastUpdateTime(0)
    , mHistorySize(DEFAULT_HISTORY_SIZE)
    , mHistoryIndex(0)
{
    mRMSHistory.reserve(mHistorySize);
}
 
Silence::~Silence() FL_NO_EXCEPT = default;
 
void Silence::update(shared_ptr<Context> context) FL_NO_EXCEPT {
    mCurrentRMS = context->getRMS();
    u32 timestamp = context->getTimestamp();
    mLastUpdateTime = timestamp;
 
    // Build history
    if (mRMSHistory.size() < static_cast<fl::size>(mHistorySize)) {
        mRMSHistory.push_back(mCurrentRMS);
    } else {
        mRMSHistory[mHistoryIndex] = mCurrentRMS;
        mHistoryIndex = (mHistoryIndex + 1) % mHistorySize;
    }
 
    // Get smoothed RMS
    float smoothedRMS = getSmoothedRMS();
 
    // Check silence condition with hysteresis
    bool nowSilent = checkSilenceCondition(smoothedRMS);
 
    // State transition logic
    if (nowSilent && !mPreviousSilent) {
        // Entering silence
        mSilenceStartTime = timestamp;
        mPreviousSilent = true;
    } else if (!nowSilent && mPreviousSilent) {
        // Exiting silence
        mSilenceEndTime = timestamp;
        u32 duration = mSilenceEndTime - mSilenceStartTime;
 
        // Only fire callbacks if minimum duration was met
        if (mIsSilent && duration >= mMinSilenceDuration) {
            mPendingEvent = PendingSilenceEvent::kEnd;
            mPendingDuration = duration;
        }
 
        mIsSilent = false;
        mPreviousSilent = false;
        mSilenceStartTime = 0;
    } else if (nowSilent && mPreviousSilent) {
        // Continuing silence
        u32 duration = timestamp - mSilenceStartTime;
 
        // Check if we've reached minimum duration and should fire start event
        if (!mIsSilent && duration >= mMinSilenceDuration) {
            mIsSilent = true;
            mPendingEvent = PendingSilenceEvent::kStart;
        }
 
        // Check if we've exceeded maximum duration
        if (mIsSilent && mMaxSilenceDuration > 0 && duration >= mMaxSilenceDuration) {
            mPendingEvent = PendingSilenceEvent::kMaxDuration;
            mPendingDuration = duration;
        }
    }
}
 
void Silence::fireCallbacks() FL_NO_EXCEPT {
    switch (mPendingEvent) {
    case PendingSilenceEvent::kStart:
        if (onSilenceStart) onSilenceStart();
        if (onSilence) onSilence(255);
        break;
    case PendingSilenceEvent::kEnd:
        if (onSilenceEnd) onSilenceEnd();
        if (onSilence) onSilence(0);
        if (onSilenceDuration) onSilenceDuration(mPendingDuration);
        break;
    case PendingSilenceEvent::kMaxDuration:
        if (onSilenceDuration) onSilenceDuration(mPendingDuration);
        break;
    case PendingSilenceEvent::kNone:
        break;
    }
    mPendingEvent = PendingSilenceEvent::kNone;
}
 
void Silence::reset() FL_NO_EXCEPT {
    mIsSilent = false;
    mPreviousSilent = false;
    mCurrentRMS = 0.0f;
    mSilenceStartTime = 0;
    mSilenceEndTime = 0;
    mLastUpdateTime = 0;
    mRMSHistory.clear();
    mHistoryIndex = 0;
}
 
float Silence::getSmoothedRMS() FL_NO_EXCEPT {
    if (mRMSHistory.empty()) {
        return 0.0f;
    }
 
    float sum = 0.0f;
    for (fl::size i = 0; i < mRMSHistory.size(); i++) {
        sum += mRMSHistory[i];
    }
    return sum / static_cast<float>(mRMSHistory.size());
}
 
bool Silence::checkSilenceCondition(float smoothedRMS) FL_NO_EXCEPT {
    // Use hysteresis to prevent rapid toggling
    // When currently silent, use a higher threshold to exit
    // When not silent, use a lower threshold to enter
    if (mPreviousSilent) {
        // Currently in potential silence - need louder signal to exit
        float exitThreshold = mSilenceThreshold * (1.0f + mHysteresis);
        return smoothedRMS <= exitThreshold;
    } else {
        // Currently not silent - need quiet signal to enter
        float enterThreshold = mSilenceThreshold * (1.0f - mHysteresis);
        return smoothedRMS <= enterThreshold;
    }
}
 
u32 Silence::getSilenceDuration() const FL_NO_EXCEPT {
    if (!mIsSilent || mSilenceStartTime == 0) {
        return 0;
    }
    return mLastUpdateTime - mSilenceStartTime;
}
 
} // namespace detector
} // namespace audio
} // namespace fl