Issue with Noise or Distortion Sound During Audio Recording Using PR #85

[isandeepj]

Hello @hiroshihorie and team,

I have been exploring the audio recording feature introduced in Pull Request #85. I'm utilizing the Room.audioProcessingModule.capturePostProcessingDelegate for this purpose, however, I am encountering an issue where the recorded audio has a noise or distortion sound.

Here is a link to the AudioRecorderHandler implementation I am using:
AudioRecorderHandler.zip

I have checked the sample rates, bit depths, buffer sizes, and codec settings to ensure they are configured correctly, but the issue persists. I suspect it might be related to the audio processing settings or possibly a mismatch in configuration somewhere.

Could you please provide some insight or assistance on how I might resolve this? I would really appreciate any help or guidance you can provide.

Thank you for your time and consideration.

Best regards,
Sandeep

[isandeepj]

@hiroshihorie can you please give your input on this!

[hiroshihorie]

Hey did you figure it out ?

[isandeepj]

Yes, for 32-bit floating-point audio data, the range is typically from -1.0 to 1.0. However, the audio frame sample range is not within this range, so it needs to be downscaled by a factor of 32768.

channelStride: 1
frameIndex: 0 sampleValue: -202.04233
frameIndex: 1 sampleValue: -165.478
frameIndex: 2 sampleValue: -436.00348
frameIndex: 3 sampleValue: -783.46893
frameIndex: 4 sampleValue: -753.1802
frameIndex: 5 sampleValue: -294.75992
frameIndex: 6 sampleValue: 152.50293
frameIndex: 7 sampleValue: 213.2728
frameIndex: 8 sampleValue: -2.9370422
frameIndex: 9 sampleValue: -132.95068
frameIndex: 10 sampleValue: -59.72957
frameIndex: 11 sampleValue: 9.903137
frameIndex: 12 sampleValue: -86.191154
... 

private func convertToPCMBuffer(_ audioBuffer: RTCAudioBuffer) -> AVAudioPCMBuffer? {
    // ... (rest of code)

    for channelIndex in 0..<numChannels {
        let audioBufferPointer = audioBuffer.rawBuffer(forChannel: channelIndex)

        guard let targetBufferPointer = pcmBuffer.floatChannelData?[channelIndex] else {
            print("Failed to get target buffer for channel \(channelIndex)")
            return nil
        }
        // Now normalize and copy the data
        var targetChannelPointer = targetBufferPointer
        let normalizationFactor: Float = 32768.0  // This value is used to normalize the audio sample values
        for frameIndex in 0..<numFrames {
            let sampleValue = audioBufferPointer[frameIndex]
            let normalizedSampleValue = sampleValue / normalizationFactor  // Normalizing the sample value
            targetChannelPointer[frameIndex * channelStride] = normalizedSampleValue
        }
    }

    // ... (rest of code)
}