AVPlayer不渲染到其AVPlayerLayer
我有一个AVPlayerLayer（CALayer的子类），我需要进入可以传递给QCRenderer的图像类型（QCRenderer接受NSImages和CIImages）。我可以将CALayer转换为CGImageRef，并将其转换为NSImage，但是内容始终清晰。
我已将其缩小到以下两个原因之一：
我没有收到任何错误，并找到一些有关转换CALayers的文档。 另外，我将AVPlayerLayer添加到NSView，它仍然是空的，所以我认为2是问题。
我正在使用Apple的AVPlayerDemo的AVPlayerDemoPlaybackViewController的修改版本。 我把它变成了一个NSObject，因为我把所有的接口代码都剥离了出来。
我在创建AVPlayer时在（void）prepareToPlayAsset：withKeys：方法中创建AVPlayerLayer：（我只是将该图层添加到NSView以测试它是否工作。）
if (![self player])
{
/* Get a new AVPlayer initialized to play the specified player item. */
[self setPlayer:[AVPlayer playerWithPlayerItem:self.mPlayerItem]];
/* Observe the AVPlayer "currentItem" property to find out when any
AVPlayer replaceCurrentItemWithPlayerItem: replacement will/did
occur.*/
[self.player addObserver:self
forKeyPath:kCurrentItemKey
options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew
context:AVPlayerDemoPlaybackViewControllerCurrentItemObservationContext];
mPlaybackView = [AVPlayerLayer playerLayerWithPlayer:self.player];
[self.theView setWantsLayer:YES];
[mPlaybackView setFrame:self.theView.layer.bounds];
[self.theView.layer addSublayer:mPlaybackView];
}
然后我创建一个NSRunLoop来每秒抓取一次AVPlayerLayer帧30次：
framegrabTimer = [NSTimer timerWithTimeInterval:(1/30) target:self selector:@selector(grabFrameFromMovie) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:framegrabTimer forMode:NSDefaultRunLoopMode];
这里是我用来抓取框架并将其传递给处理QCRenderer的类的代码：
-(void)grabFrameFromMovie {
CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
CGContextRef theContext = CGBitmapContextCreate(NULL, mPlaybackView.frame.size.width, mPlaybackView.frame.size.height, 8, 4*mPlaybackView.frame.size.width, colorSpace, kCGImageAlphaPremultipliedLast);
[mPlaybackView renderInContext:theContext];
CGImageRef CGImage = CGBitmapContextCreateImage(theContext);
NSImage *image = [[NSImage alloc] initWithCGImage:CGImage size:NSMakeSize(mPlaybackView.frame.size.width, mPlaybackView.frame.size.height)];
[[NSNotificationCenter defaultCenter] postNotificationName:@"AVPlayerLoadedNewFrame" object:[image copy]];
CGContextRelease(theContext);
CGColorSpaceRelease(colorSpace);
CGImageRelease(CGImage); }
我无法弄清楚为什么我只能说清楚。 任何帮助都非常感谢，因为OS X没有足够的AVFoundation文档。
它的作品对我来说：
AVAssetImageGenerator *gen = [[AVAssetImageGenerator alloc] initWithAsset:[[[self player] currentItem] asset]];
CGImageRef capture = [gen copyCGImageAtTime:self.player.currentTime actualTime:NULL error:NULL];
NSImage *img = [[NSImage alloc] initWithCGImage:capture size:self.playerView.frame.size];
您可以将AVPlayerItemVideoOutput添加到AVPlayerItem，然后调用copyPixelBufferForItemTime来查询包含指定时间帧的CVPixelBufferRef对象，以下是示例代码：
NSDictionary *pixBuffAttributes = @{
(id)kCVPixelBufferWidthKey:@(nWidth),
(id)kCVPixelBufferHeightKey:@(nHeight),
(id)kCVPixelBufferCGImageCompatibilityKey:@YES,
};
m_output = [[AVPlayerItemVideoOutput alloc] initWithPixelBufferAttributes:pixBuffAttributes];
...
m_buffer = [m_output copyPixelBufferForItemTime:time itemTimeForDisplay:NULL];
CVPixelBufferLockBaseAddress(m_buffer, 0);
auto *buffer = CVPixelBufferGetBaseAddress(m_buffer);
frame->width = CVPixelBufferGetWidth(m_buffer);
frame->height = CVPixelBufferGetHeight(m_buffer);
frame->widthbytes = CVPixelBufferGetBytesPerRow(m_buffer);
frame->bufferlen = frame->widthbytes * (uint32)CVPixelBufferGetHeight(m_buffer);
auto &videoInfo = m_info.video;
CGDataProviderRef dp = CGDataProviderCreateWithData(nullptr, buffer, frame->bufferlen, nullptr);
CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
m_image = CGImageCreate(frame->width,
frame->height,
8,
videoInfo.pixelbits,
frame->widthbytes,
cs,
kCGImageAlphaNoneSkipFirst,
dp,
nullptr,
true,
kCGRenderingIntentDefault);
CGColorSpaceRelease(cs);
CGDataProviderRelease(dp);
你可以结账苹果的官方样品：
实时timeVideoProcessingUsingAVPlayerItemVideoOutput
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