ios - 如何在 Objective C 中编写以下代码？

Question

我将下面的代码从 swift 转换为 Objective C:

func toPCMBuffer(data: NSData) -> AVAudioPCMBuffer {
        let audioFormat = AVAudioFormat(commonFormat: AVAudioCommonFormat.pcmFormatFloat32, sampleRate: 8000, channels: 1, interleaved: false)  // given NSData audio format
        let PCMBuffer = AVAudioPCMBuffer(pcmFormat: audioFormat, frameCapacity: UInt32(data.length) / audioFormat.streamDescription.pointee.mBytesPerFrame)
        PCMBuffer.frameLength = PCMBuffer.frameCapacity
        let channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: Int(PCMBuffer.format.channelCount))
        data.getBytes(UnsafeMutableRawPointer(channels[0]) , length: data.length)
        return PCMBuffer
    }

我转换为 objective-c :

-(AVAudioPCMBuffer*)toPCMBuffer: (NSData*)data {

    AVAudioFormat * audioFormat = [[AVAudioFormat alloc]initWithCommonFormat:AVAudioPCMFormatFloat32 sampleRate:8000 channels:1 interleaved:false];
    AVAudioPCMBuffer* PCMBuffer = [[AVAudioPCMBuffer alloc]initWithPCMFormat:audioFormat frameCapacity:data.length/audioFormat.streamDescription->mBytesPerFrame];
    PCMBuffer.frameLength = PCMBuffer.frameCapacity;
    float *channels = malloc(PCMBuffer.format.channelCount * sizeof(float)); // remember to free eventually
    memcpy(channels, PCMBuffer.floatChannelData, PCMBuffer.format.channelCount * sizeof(float));
    [data getBytes:channels length:data.length];
    return PCMBuffer;

}

但我不确定是否更正行代码:

AVAudioPCMBuffer* PCMBuffer = [[AVAudioPCMBuffer alloc]initWithPCMFormat:audioFormat frameCapacity:data.length/audioFormat.streamDescription->mBytesPerFrame];

这是我不知道如何将 UInt32(data.length) 写入 objective-c 的代码

和:

如何将UnsafeMutableRawPointer(channels[0])转换为objc？

[data getBytes:channels length:data.length];

Answer 1

原始代码的作用是将参数data复制到PCMBuffer.floatChannelData中。

您的代码所做的是创建一个新的字节缓冲区，然后将该空缓冲区复制到 PCMBuffer 并将参数数据复制到缓冲区中。

我相信它应该类似于:

PCMBuffer.frameLength = PCMBuffer.frameCapacity;
[data getBytes:PCMBuffer.floatChannelData length:data.length];
return PCMBuffer;