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我正在使用 AudioConverter 将通过 AVCaptureSession 捕获的未压缩 CMSampleBuffer 转换为 AudioBufferList：

let packetDescriptionsPtr = UnsafeMutablePointer<AudioStreamPacketDescription>.allocate(capacity: 1)

AudioConverterFillComplexBuffer(
                converter,
                inputDataProc,
                Unmanaged.passUnretained(self).toOpaque(),
                &ioOutputDataPacketSize,
                outOutputData.unsafeMutablePointer,
                packetDescriptionsPtr
            )

然后，我使用如下数据包描述构造一个包含压缩数据的 CMSampleBuffer：

CMAudioSampleBufferCreateWithPacketDescriptions(
        allocator: kCFAllocatorDefault,
        dataBuffer: nil,
        dataReady: false,
        makeDataReadyCallback: nil,
        refcon: nil,
        formatDescription: formatDescription!,
        sampleCount: Int(data.unsafePointer.pointee.mNumberBuffers),
        presentationTimeStamp: presentationTimeStamp,
        packetDescriptions: &packetDescriptions,
        sampleBufferOut: &sampleBuffer)

当我尝试使用 AVAssetWriter 保存缓冲区时，出现以下错误：-[AVAssetWriterInput appendSampleBuffer:] Cannot append sample buffer: First input buffer must have an appropriate kCMSampleBufferAttachmentKey_TrimDurationAtStart since the codec has encoder delay'

我决定准备前三个缓冲区，因为每个缓冲区的长度都是一致的：

if self.receivedAudioBuffers < 2 {
                    let primingDuration = CMTimeMake(value: 1024, timescale: 44100)
                    CMSetAttachment(sampleBuffer,
                                    key: kCMSampleBufferAttachmentKey_TrimDurationAtStart,
                                    value: CMTimeCopyAsDictionary(primingDuration, allocator: kCFAllocatorDefault),
                                    attachmentMode: kCMAttachmentMode_ShouldNotPropagate)
                    self.receivedAudioBuffers += 1
                }
                else if self.receivedAudioBuffers == 2 {
                    let primingDuration = CMTimeMake(value: 64, timescale: 44100)
                    CMSetAttachment(sampleBuffer,
                                    key: kCMSampleBufferAttachmentKey_TrimDurationAtStart,
                                    value: CMTimeCopyAsDictionary(primingDuration, allocator: kCFAllocatorDefault),
                                    attachmentMode: kCMAttachmentMode_ShouldNotPropagate)
                    self.receivedAudioBuffers += 1
                }

现在我不再收到错误，并且在附加样本时也没有收到任何错误，但音频不会在录制中播放，并且还会弄乱整个视频文件（似乎计时信息已损坏）。

这里有什么我想念的吗？我应该如何正确附加音频 CMSampleBuffer？

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