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      Latest reply on Jan 21, 2020 3:12 PM by gaperlinski
      gaperlinski Level 1 Level 1 (0 points)

        I'm trying to compress input from AVCaptureSession and save it to an .mp4 file. I've managed to convert and save video without issues but am having trouble with audio.

        I've reached a point where I'm able to convert audio samples to AAC and I can save the converted CMSampleBuffer to .mp4 but when I play it back on the iPhone, the audio sounds distorted. Click here to download a sample file.

         

        I'm passing the following format to the converter:

        AudioStreamBasicDescription(mSampleRate: 44_100, 
        mFormatID: kAudioFormatMPEG4AAC, 
        mFormatFlags: UInt32(MPEG4ObjectID.AAC_LC.rawValue), 
        mBytesPerPacket: 0, 
        mFramesPerPacket: 1024, 
        mBytesPerFrame: 0, 
        mChannelsPerFrame: 2,
        mBitsPerChannel: 0, 
        mReserved: 0)
        
        

        I'm not sure if this is an issue with audio conversion or with writing the file. Here's a link to a sample project with just the audio stream conversion and writing: https://github.com/gaperlinski/AudioConversion (follow the instructions in README.MD to reproduce the issue)

         

        Is there anything obvious I'm doing wrong that causes the audio to sound like that?