从TrueDepth相机保存深度图像

对于“原始”深度/视差图,没有标准的视频格式,这可能与AVCapture有关,而不是真正提供记录它的方法。

这里有几个值得研究的选项:

1. 将深度贴图转换为灰度纹理(可以使用 AVCamPhotoFilter 示例代码),然后将这些纹理传递给 AVAssetWriter 生成灰度视频。根据您选择的视频格式和灰度转换方法,您为读取视频而编写的其他软件可能能够从灰度帧中以足够的精度恢复深度/视差信息。

2. 只要你有 CVPixelBuffer ,您可以自己获取数据并对其执行任何操作。使用 CVPixelBufferLockBaseAddress (带有 readOnly 标记)以确保内容在读取时不会更改,然后从指针复制数据 CVPixelBufferGetBaseAddress 提供给您想要的任何地方。(使用其他像素缓冲区功能查看要复制的字节数,并在完成后解锁缓冲区。)

   不过,请注意:如果您花费太多时间从缓冲区复制或以其他方式保留缓冲区,它们将不会被释放,因为新的缓冲区来自捕获系统,您的捕获会话将挂起。(总的来说,如果不测试一台设备是否有足够的内存和I/O带宽,以这种方式进行大量记录,我们就不清楚了。)

您可以使用压缩库使用原始CVPixelBuffer数据创建zip文件。 此解决方案几乎没有问题。

1. 它包含大量数据,而zip不是一个好的压缩。(压缩文件比相同帧数的每帧32位视频大20倍)。
2. 苹果的压缩库创建了一个标准zip程序无法打开的文件。我在C代码中使用zlib来读取它并使用 inflateInit2(&strm, -15); 让它发挥作用。
3. 您需要做一些工作才能将文件从应用程序中导出

这是我的代码(我将其限制为250帧,因为它保存在RAM中,但如果需要更多帧,您可以刷新到磁盘):

//  DepthCapture.swift
//  AVCamPhotoFilter
//
//  Created by Eyal Fink on 07/04/2018.
//  Copyright © 2018 Resonai. All rights reserved.
//
// Capture the depth pixelBuffer into a compress file.
// This is very hacky and there are lots of TODOs but instead we need to replace
// it with a much better compression (video compression)....

import AVFoundation
import Foundation
import Compression


class DepthCapture {
    let kErrorDomain = "DepthCapture"
    let maxNumberOfFrame = 250
    lazy var bufferSize = 640 * 480 * 2 * maxNumberOfFrame  // maxNumberOfFrame frames
    var dstBuffer: UnsafeMutablePointer<UInt8>?
    var frameCount: Int64 = 0
    var outputURL: URL?
    var compresserPtr: UnsafeMutablePointer<compression_stream>?
    var file: FileHandle?

    // All operations handling the compresser oobjects are done on the
    // porcessingQ so they will happen sequentially
    var processingQ = DispatchQueue(label: "compression",
                                    qos: .userInteractive)


    func reset() {
        frameCount = 0
        outputURL = nil
        if self.compresserPtr != nil {
            //free(compresserPtr!.pointee.dst_ptr)
            compression_stream_destroy(self.compresserPtr!)
            self.compresserPtr = nil
        }
        if self.file != nil {
            self.file!.closeFile()
            self.file = nil
        }
    }
    func prepareForRecording() {
        reset()
        // Create the output zip file, remove old one if exists
        let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
        self.outputURL = URL(fileURLWithPath: documentsPath.appendingPathComponent("Depth"))
        FileManager.default.createFile(atPath: self.outputURL!.path, contents: nil, attributes: nil)
        self.file = FileHandle(forUpdatingAtPath: self.outputURL!.path)
        if self.file == nil {
            NSLog("Cannot create file at: \(self.outputURL!.path)")
            return
        }

        // Init the compression object
        compresserPtr = UnsafeMutablePointer<compression_stream>.allocate(capacity: 1)
        compression_stream_init(compresserPtr!, COMPRESSION_STREAM_ENCODE, COMPRESSION_ZLIB)
        dstBuffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
        compresserPtr!.pointee.dst_ptr = dstBuffer!
        //defer { free(bufferPtr) }
        compresserPtr!.pointee.dst_size = bufferSize


    }
    func flush() {
        //let data = Data(bytesNoCopy: compresserPtr!.pointee.dst_ptr, count: bufferSize, deallocator: .none)
        let nBytes = bufferSize - compresserPtr!.pointee.dst_size
        print("Writing \(nBytes)")
        let data = Data(bytesNoCopy: dstBuffer!, count: nBytes, deallocator: .none)
        self.file?.write(data)
    }

    func startRecording() throws {
        processingQ.async {
            self.prepareForRecording()
        }
    }
    func addPixelBuffers(pixelBuffer: CVPixelBuffer) {
        processingQ.async {
            if self.frameCount >= self.maxNumberOfFrame {
                // TODO now!! flush when needed!!!
                print("MAXED OUT")
                return
            }

            CVPixelBufferLockBaseAddress(pixelBuffer, .readOnly)
            let add : UnsafeMutableRawPointer = CVPixelBufferGetBaseAddress(pixelBuffer)!
            self.compresserPtr!.pointee.src_ptr = UnsafePointer<UInt8>(add.assumingMemoryBound(to: UInt8.self))
            let height = CVPixelBufferGetHeight(pixelBuffer)
            self.compresserPtr!.pointee.src_size = CVPixelBufferGetBytesPerRow(pixelBuffer) * height
            let flags = Int32(0)
            let compression_status = compression_stream_process(self.compresserPtr!, flags)
            if compression_status != COMPRESSION_STATUS_OK {
                NSLog("Buffer compression retured: \(compression_status)")
                return
            }
            if self.compresserPtr!.pointee.src_size != 0 {
                NSLog("Compression lib didn't eat all data: \(compression_status)")
                return
            }
            CVPixelBufferUnlockBaseAddress(pixelBuffer, .readOnly)
            // TODO(eyal): flush when needed!!!
            self.frameCount += 1
            print("handled \(self.frameCount) buffers")
        }
    }
    func finishRecording(success: @escaping ((URL) -> Void)) throws {
        processingQ.async {
            let flags = Int32(COMPRESSION_STREAM_FINALIZE.rawValue)
            self.compresserPtr!.pointee.src_size = 0
            //compresserPtr!.pointee.src_ptr = UnsafePointer<UInt8>(0)
            let compression_status = compression_stream_process(self.compresserPtr!, flags)
            if compression_status != COMPRESSION_STATUS_END {
                NSLog("ERROR: Finish failed. compression retured: \(compression_status)")
                return
            }
            self.flush()
            DispatchQueue.main.sync {
                success(self.outputURL!)
            }
            self.reset()
        }
    }
}