如何手动释放CMSampleBuffer

Question

此代码导致内存泄漏和应用程序崩溃：

    var outputSamples = [Float]()

    assetReader.startReading()
    while assetReader.status == .reading {
        let trackOutput = assetReader.outputs.first!

        if let sampleBuffer = trackOutput.copyNextSampleBuffer(),
            let blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer) {
            let blockBufferLength = CMBlockBufferGetDataLength(blockBuffer)
            let sampleLength = CMSampleBufferGetNumSamples(sampleBuffer) * channelCount(from: assetReader)
            var data = Data(capacity: blockBufferLength)
            data.withUnsafeMutableBytes { (blockSamples: UnsafeMutablePointer<Int16>) in
                CMBlockBufferCopyDataBytes(blockBuffer, atOffset: 0, dataLength: blockBufferLength, destination: blockSamples)
                CMSampleBufferInvalidate(sampleBuffer)

                let processedSamples = process(blockSamples,
                                               ofLength: sampleLength,
                                               from: assetReader,
                                               downsampledTo: targetSampleCount)
                outputSamples += processedSamples
            }
        }
    }
    var paddedSamples = [Float](repeating: silenceDbThreshold, count: targetSampleCount)
    paddedSamples.replaceSubrange(0..<min(targetSampleCount, outputSamples.count), with: outputSamples)

这是由于 copyNextSampleBuffer() and The Create Rule。

反过来，我们不能在Swift中使用CFRelease()。 link 到 Objective-C only 规则的原因超出了我的理解。

有没有办法在Swift中手动释放CMSampleBuffer？

Answer 1

这不是真正的解决方案，因为手动释放内存似乎是不可能的，并且将 while 循环与 assetReader 结合使用会导致在读取不安全的可变字节时不会释放内存。

问题已通过解决方法解决：在将音频文件暴露给 while 循环之前将其转换为 CAF 格式。

缺点：需要一秒钟的时间，音频文件越长 - 花费的时间越多。

好处：它只使用了极少量的内存，这才是问题的首要所在。

灵感来自：https://whosebug.com/users/2907715/carpsen90 answer in

Answer 2

我最近使用自动释放池解决了类似的问题

尝试将 sampleBuffer 使用的区域包裹在自动释放池中。像这样：

var outputSamples = [Float]()

assetReader.startReading()
while assetReader.status == .reading {
    let trackOutput = assetReader.outputs.first!

    autoreleasepool {
        if let sampleBuffer = trackOutput.copyNextSampleBuffer(),
            let blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer) {
            let blockBufferLength = CMBlockBufferGetDataLength(blockBuffer)
            let sampleLength = CMSampleBufferGetNumSamples(sampleBuffer) * channelCount(from: assetReader)
            var data = Data(capacity: blockBufferLength)
            data.withUnsafeMutableBytes { (blockSamples: UnsafeMutablePointer<Int16>) in
                CMBlockBufferCopyDataBytes(blockBuffer, atOffset: 0, dataLength: blockBufferLength, destination: blockSamples)
                CMSampleBufferInvalidate(sampleBuffer)

                let processedSamples = process(blockSamples,
                                               ofLength: sampleLength,
                                               from: assetReader,
                                               downsampledTo: targetSampleCount)
                outputSamples += processedSamples
            }
        }
    }
}
var paddedSamples = [Float](repeating: silenceDbThreshold, count: targetSampleCount)
paddedSamples.replaceSubrange(0..<min(targetSampleCount, outputSamples.count), with: outputSamples)

如果我没理解错的话，一旦移出autoreleasepool的范围，sampleBuffer就会被释放

如何手动释放CMSampleBuffer

How to manually release CMSampleBuffer

cmsamplebuffer

swift

swift4.2