iOS Swift malloc 错误

Question

我想在 iOS 上实时录制音频，分析原始音频数据并保存部分录制数据。我正在使用以下代码记录数据:https://gist.github.com/hotpaw2/ba815fc23b5d642705f2b1dedfaf0107

现在，我的数据保存在一个 Float 数组中，我想将它保存到一个音频文件中。我试着用这段代码来做:

let fileMgr = FileManager.default
    let dirPaths = fileMgr.urls(for: .documentDirectory, in: .userDomainMask)
    let recordSettings = [AVEncoderAudioQualityKey: AVAudioQuality.min.rawValue,
                      AVEncoderBitRateKey: 16,
                      AVNumberOfChannelsKey: 2,
                      AVSampleRateKey: 44100] as [String: Any]
    let soundFileUrl = dirPaths[0].appendingPathComponent("recording-" + getDate() + ".pcm")


    do {
        let audioFile = try AVAudioFile(forWriting: soundFileUrl, settings: recordSettings)
        let format = AVAudioFormat(commonFormat: .pcmFormatInt16, sampleRate: 44100, channels: 2, interleaved: true)

        let audioFileBuffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: 3000)

        for i in 0..<circBuffer.count {
            audioFileBuffer.int16ChannelData?.pointee[i] = Int16(circBuffer[i])
        }

        try audioFile.write(from: audioFileBuffer)

    }

在最后一行，我收到一条错误消息:

错误:>avae> AVAudioFile.mm:306: -[AVAudioFile writeFromBuffer:error:]: error -50 amplitudeDemo(79264,0x70000f7cb000) malloc:* 对象 0x7fc5b9057e00 错误:释放对象的校验和不正确 - 对象可能在释放后被修改。 * 在malloc_error_break 设置断点调试

我已经搜索了很多其他问题，但找不到任何对我有帮助的问题。

Answer 1

在您的代码中这一行:

let audioFileBuffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: 3000)

您声明一个容量为 3000 帧 * 2 个 channel 的 AVAudioPCMBuffer，这意味着为您的 audioFileBuffer 分配的缓冲区可以包含 6000 个样本。如果 channel 数据的索引超过此限制，您的代码会破坏堆中的附近区域，这会导致对象可能已被修改错误。

因此，您的 circBuffer.count 可能超过了这个限制。您需要为 AVAudioPCMBuffer 分配足够的缓冲区大小。

    do {
        //### You need to specify common format
        let audioFile = try AVAudioFile(forWriting: soundFileUrl, settings: recordSettings, commonFormat: .pcmFormatInt16, interleaved: true)

        let channels = 2
        let format = AVAudioFormat(commonFormat: .pcmFormatInt16, sampleRate: 44100, channels: AVAudioChannelCount(channels), interleaved: true)
        let audioFileBuffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: AVAudioFrameCount(circBuffer.count / channels)) //<-allocate enough frames
        //### `stride` removed as it seems useless...
        let int16ChannelData = audioFileBuffer.int16ChannelData! //<-cannot be nil for the `format` above

        //When interleaved, channel data of AVAudioPCMBuffer is not as described in its doc:
        //  https://developer.apple.com/reference/avfoundation/avaudiopcmbuffer/1386212-floatchanneldata .
        //  The following code is modified to work with actual AVAudioPCMBuffer.
        //Assuming `circBuffer` as
        //  Interleaved, 2 channel, Float32
        //  Each sample is normalized to [-1.0, 1.0] (as usual floating point audio format)
        for i in 0..<circBuffer.count {
            int16ChannelData[0][i] = Int16(circBuffer[i] * Float(Int16.max))
        }
        //You need to update `frameLength` of the `AVAudioPCMBuffer`.
        audioFileBuffer.frameLength = AVAudioFrameCount(circBuffer.count / channels)

        try audioFile.write(from: audioFileBuffer)

    } catch {
        print("Error", error)
    }

一些注释添加为注释，请在尝试此代码之前检查它们。

---

更新 抱歉，为了显示未经测试的代码，修复了两件事:

• 实例化AVAudioFile时需要指定commonFormat:。
• int16ChannelData(和其他 channel 数据)在交错时不返回其文档中所述的预期指针，修改数据填充循环以适应实际行为。

请尝试。