如何使用 CMSampleBuffer 创建 AVAudioPCMBuffer？答案

【问题标题】：How to create AVAudioPCMBuffer with CMSampleBuffer?如何使用 CMSampleBuffer 创建 AVAudioPCMBuffer？
【发布时间】：2023-03-13 15:53:01
【问题描述】：

我有一个AVAsset，我使用AVAssetReaderAudioMixOutput 得到CMSampleBuffer，我想使用这个CMSampleBuffer 来创建AVAudioPlayerNode 到scheduleBuffer

怎么做，有大佬帮忙吗？

【问题讨论】：

标签： ios swift avfoundation audiotoolbox

【解决方案1】：

extension AVAudioPCMBuffer {
    static func create(from sampleBuffer: CMSampleBuffer) -> AVAudioPCMBuffer? {
        
        guard let description: CMFormatDescription = CMSampleBufferGetFormatDescription(sampleBuffer),
              let sampleRate: Float64 = description.audioStreamBasicDescription?.mSampleRate,
              let channelsPerFrame: UInt32 = description.audioStreamBasicDescription?.mChannelsPerFrame /*,
                                                                                                         let numberOfChannels = description.audioChannelLayout?.numberOfChannels */
        else { return nil }
        
        guard let blockBuffer: CMBlockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer) else {
            return nil
        }
        
        let samplesCount = CMSampleBufferGetNumSamples(sampleBuffer)
        
        //let length: Int = CMBlockBufferGetDataLength(blockBuffer)
        
        let audioFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: sampleRate, channels: AVAudioChannelCount(1), interleaved: false)
        
        let buffer = AVAudioPCMBuffer(pcmFormat: audioFormat!, frameCapacity: AVAudioFrameCount(samplesCount))!
        buffer.frameLength = buffer.frameCapacity
        
        // GET BYTES
        var dataPointer: UnsafeMutablePointer<Int8>?
        CMBlockBufferGetDataPointer(blockBuffer, atOffset: 0, lengthAtOffsetOut: nil, totalLengthOut: nil, dataPointerOut: &dataPointer)
        
        guard var channel: UnsafeMutablePointer<Float> = buffer.floatChannelData?[0],
              let data = dataPointer else { return nil }
        
        var data16 = UnsafeRawPointer(data).assumingMemoryBound(to: Int16.self)
        
        for _ in 0...samplesCount - 1 {
            channel.pointee = Float32(data16.pointee) / Float32(Int16.max)
            channel += 1
            for _ in 0...channelsPerFrame - 1 {
                data16 += 1
            }
            
        }
        
        return buffer
    }
}

【讨论】：