我的目标是将 iDevice 的屏幕镜像到 OSX，尽可能无延迟。
据我所知，有两种方法：
Airplay Mirroring（例如反射器）CoreMediaIO通过 Lightning（例如 Quicktime Recording）
我选择了第二种方法，因为（据我所知）连接的 iDevice 可以在一次性设置后自动识别为 DAL 设备。
如何做到这一点的主要资源是这个博客：https ://nadavrub.wordpress.com/2015/07/06/macos-media-capture-using-coremediaio/
该博客非常深入地介绍了如何使用CoreMediaIO，但是AVFoundation一旦您将连接的 iDevice 识别为AVCaptureDevice.
这个问题：如何通过USB镜像iOS屏幕？已经发布了一个关于如何抓取 iDevice 提供的 H264（附件 B）muxxed 数据流的每一帧的解决方案。
但是，我的问题是VideoToolbox无法正确解码（错误代码 -8969，BadData），即使代码不应该有任何差异。
vtDecompressionDuctDecodeSingleFrame 在 /SourceCache/CoreMedia_frameworks/CoreMedia-1562.240/Sources/VideoToolbox/VTDecompressionSession.c 第 3241 行发出 err=-8969 (err)（VTVideoDecoderDecodeFrame 返回错误）
完整代码：
#import "ViewController.h"
@import CoreMediaIO;
@import AVFoundation;
@import AppKit;
@implementation ViewController
AVCaptureSession *session;
AVCaptureDeviceInput *newVideoDeviceInput;
AVCaptureVideoDataOutput *videoDataOutput;
- (void)viewDidLoad {
[super viewDidLoad];
}
- (instancetype)initWithCoder:(NSCoder *)coder
{
self = [super initWithCoder:coder];
if (self) {
// Allow iOS Devices Discovery
CMIOObjectPropertyAddress prop =
{ kCMIOHardwarePropertyAllowScreenCaptureDevices,
kCMIOObjectPropertyScopeGlobal,
kCMIOObjectPropertyElementMaster };
UInt32 allow = 1;
CMIOObjectSetPropertyData( kCMIOObjectSystemObject,
&prop, 0, NULL,
sizeof(allow), &allow );
// Get devices
NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeMuxed];
BOOL deviceAttahced = false;
for (int i = 0; i < [devices count]; i++) {
AVCaptureDevice *device = devices[i];
if ([[device uniqueID] isEqualToString:@"b48defcadf92f300baf5821923f7b3e2e9fb3947"]) {
deviceAttahced = true;
[self startSession:device];
break;
}
}
}
return self;
}
- (void) deviceConnected:(AVCaptureDevice *)device {
if ([[device uniqueID] isEqualToString:@"b48defcadf92f300baf5821923f7b3e2e9fb3947"]) {
[self startSession:device];
}
}
- (void) startSession:(AVCaptureDevice *)device {
// Init capturing session
session = [[AVCaptureSession alloc] init];
// Star session configuration
[session beginConfiguration];
// Add session input
NSError *error;
newVideoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (newVideoDeviceInput == nil) {
dispatch_async(dispatch_get_main_queue(), ^(void) {
NSLog(@"%@", error);
});
} else {
[session addInput:newVideoDeviceInput];
}
// Add session output
videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
videoDataOutput.videoSettings = [NSDictionary dictionaryWithObject: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey: (id)kCVPixelBufferPixelFormatTypeKey];
dispatch_queue_t videoQueue = dispatch_queue_create("videoQueue", NULL);
[videoDataOutput setSampleBufferDelegate:self queue:videoQueue];
[session addOutput:videoDataOutput];
// Finish session configuration
[session commitConfiguration];
// Start the session
[session startRunning];
}
#pragma mark - AVCaptureAudioDataOutputSampleBufferDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
//NSImage *resultNSImage = [self imageFromSampleBuffer:sampleBuffer];
//self.imageView.image = [self nsImageFromSampleBuffer:sampleBuffer];
self.imageView.image = [[NSImage alloc] initWithData:imageToBuffer(sampleBuffer)];
}
NSData* imageToBuffer( CMSampleBufferRef source) {
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(source);
CVPixelBufferLockBaseAddress(imageBuffer,0);
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
void *src_buff = CVPixelBufferGetBaseAddress(imageBuffer);
NSData *data = [NSData dataWithBytes:src_buff length:bytesPerRow * height];
CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
return data;
}