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qtqpainter

how to make smooth level(peak) meter with Qt

get peak levels from channels:

BASS_ChannelGetLevelEx(chan, levels, 0.02, BASS_LEVEL_STEREO    );

this function i call in thread with same frequency

void Thread::run()
{ 

 while(!m_abort)
    {

        emit SetLevels();
        QThread::msleep(20);
    }
}

level meter draw via QPainter

that's what happens

enter image description here

running like crazy, making sharp jumps. but must be smoothly

how make it level smoothly?

Solution

  • When your new peak value is greater than the current peak value, then just assign the new value. If it's less then decrease the current value in a logarithmic way like so..

    float factor = 0.10;
cur_left_value = cur_left_value - factor * (cur_left_value - new_left_value);

    The greater the factor is, the faster your peak meters will "fall". You will have to have a timer or thread to continuously assign the latest (new) peak values with the logic explained above.