如何使用 CMSampleBuffer 创建 AVAudioPCMBuffer？

Question

我有一个 AVAsset，我用 AVAssetReaderAudioMixOutput 得到 CMSampleBuffer，我想用这个 CMSampleBuffer 创建 AVAudioPlayerNode 到 scheduleBuffer

怎么做，有人帮忙吗？

Answer 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
    }
}

如何使用 CMSampleBuffer 创建 AVAudioPCMBuffer？

How to create AVAudioPCMBuffer with CMSampleBuffer?

avfoundation

audiotoolbox

ios

swift