The input channel's signal intensity?(db value)

Hi everyone,
How could detect the input channel’s signal intensity in DB unit in the void MainComponent::getNextAudioBlock (const AudioSourceChannelInfo& bufferToFill) function?

Best regards!

My suggestion: take the average of the absolute value of all the samples in bufferToFill, and then apply the amplitude-to-decibels formula dB = 20 * log10(A), where A is the mean amplitude (average of absolute value of buffer samples). Here is a nice resource:

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The result from the above formula is different from the setted db level. For example, when i set the db level -20 db, the computed db level is about -23 db

The crest factor of a sine is sqrt(2) (ratio between peak and RMS), and that’s 3dB


what is the sine wave db formula after plus the crest factor?

Depends. If you want to get the intensity (power/energy related) you simply calculate the RMS, however if you know it’s a sine and you want its amplitude, the you have to add 3dB to your intensity value.

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Here the signal is definite: sine wave.

    auto* inBuffer = bufferToFill.buffer->getReadPointer(1, bufferToFill.startSample);
    	float audioInSampleSum = 0.0;
    				for (auto sample = 0; sample < bufferToFill.numSamples; ++sample)
    					audioInSampleSum = audioInSampleSum + abs(inBuffer[sample])*abs(inBuffer[sample]);
    					//DBG("Decibels::gainToDecibels(inBuffer["<<sample<<"]) =" << Decibels::gainToDecibels(abs(inBuffer[sample]*sqrt(2))));
    				DBG("output signal db level::" << Decibels::gainToDecibels(sqrt(audioInSampleSum / bufferToFill.numSamples) * sqrt(2)))

Is that OK? I just want get the input signal’s DBFS value through the accessed input channel’s audio sample.捕获

You don’t need to use abs() if you are squaring the inBuffer[sample] value, but I think you’ve got it.

Here’s another nice resource I found:

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Just in case you missed it, there is a getRMSLevel() method in AudioBuffer:

auto numChannels = bufferToFill.buffer->getNumChannels();
float rms = 0;
for (int c=0; c < numChannels; ++c)
    rms += bufferToFill.buffer->getRMSLevel (c, bufferToFill.startSample, bufferToFill.numSamples);

rms /= numChannels;

I think taking the average is appropriate since the values are already RMS values. But maybe the values should be summed as squares? IDK

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