从 AAC 数据创建 CMSampleBuffer

Question

我正在使用记录音频和视频的外部摄像头。

我的应用使用以下结构接收 AAC 格式的音频：

struct AudioPacket {
   let timestamp: TimeInterval
   let data: Data
   let asbd: AudioStreamBasicDescription
   let magicCookie: Data
   let audioSpecificConfigData: Data
}

AudioStreamBasicDescription属性包含以下内容：

- mSampleRate : 48000.0
- mFormatID : 1633772320
- mFormatFlags : 0
- mBytesPerPacket : 0
- mFramesPerPacket : 1024
- mBytesPerFrame : 0
- mChannelsPerFrame : 1
- mBitsPerChannel : 0
- mReserved : 0

我正在使用AVAssetWriter将音频和视频写入文件，需要向资产编写器提供CMSampleBuffer -s。

那么如何将上述AudioPacket结构转换为CMSampleBuffer呢？

Answer 1

不是一个确切的答案，但我会尝试如下：

func convertPacket(_ packet: AudioPacket) -> CMSampleBuffer? {
    var data = packet.data
    var asbd = packet.asbd
    var magicCookie = packet.magicCookie
    var blockBuffer: CMBlockBuffer?
    var formatDescription: CMFormatDescription?
    var sampleBuffer: CMSampleBuffer?
    CMBlockBufferCreateWithMemoryBlock(
        allocator: nil, memoryBlock: &data, blockLength: data.count,
        blockAllocator: nil, customBlockSource: nil, offsetToData: 0,
        dataLength: data.count, flags: 0, blockBufferOut: &blockBuffer
    )
    CMAudioFormatDescriptionCreate(
        allocator: nil, asbd: &asbd, layoutSize: 0, layout: nil,
        magicCookieSize: magicCookie.count, magicCookie: &magicCookie,
        extensions: nil, formatDescriptionOut: &formatDescription
    )
    CMAudioSampleBufferCreateWithPacketDescriptions(
        allocator: nil, dataBuffer: blockBuffer, dataReady: true,
        makeDataReadyCallback: nil, refcon: nil, formatDescription: formatDescription!,
        sampleCount: 1, // <- provide correct number
        presentationTimeStamp: CMTime(seconds: packet.timestamp, preferredTimescale: 100),
        packetDescriptions: nil, sampleBufferOut: &sampleBuffer
    )
    return sampleBuffer
}