1.AVCaptureVideoPreviewLayer->視頻預(yù)覽layer

#import <AVFoundation/AVFoundation.h>

// AVCaptureSession 初始化即可
    self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.avSession];
    [self.previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [self.previewLayer setFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
    [self.view.layer insertSublayer:self.previewLayer above:0];

2.AVSampleBufferDisplayLayer ->視頻輸出對(duì)象CMSampleBufferRef顯示layer

// - (void)enqueueSampleBuffer:(CMSampleBufferRef)sampleBuffer;

- (void)addAVSampleBufferDisplayLayer {
    AVSampleBufferDisplayLayer * layer = [[AVSampleBufferDisplayLayer alloc] init];
    layer.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
    [layer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    self.sampleDisplayLayer = layer;
    [self.view.layer addSublayer:layer];
}

3. CMSampleBufferRef和CVPixelBufferRef相互轉(zhuǎn)換

CMSampleBufferRef-> CVPixelBufferRef

CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

CVPixelBufferRef-> CMSampleBufferRef

- (CMSampleBufferRef)getCMSampleBufferFromPixelBuffer:(CVPixelBufferRef)pixelBuffer
{
    if (!pixelBuffer){
        return NULL;
    }
    @synchronized(self) {
        if (_previousPixelBuffer) {
            CVPixelBufferRelease(_previousPixelBuffer);
        }
        _previousPixelBuffer = CVPixelBufferRetain(pixelBuffer);
    }
    
    //不設(shè)置具體時(shí)間信息
    CMSampleTimingInfo timing = {kCMTimeInvalid, kCMTimeInvalid, kCMTimeInvalid};
    //獲取視頻信息
    CMVideoFormatDescriptionRef videoInfo = NULL;
    OSStatus result = CMVideoFormatDescriptionCreateForImageBuffer(NULL, _previousPixelBuffer, &videoInfo);
    NSParameterAssert(result == 0 && videoInfo != NULL);
    
    CMSampleBufferRef sampleBuffer = NULL;
    result = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault,_previousPixelBuffer, true, NULL, NULL, videoInfo, &timing, &sampleBuffer);
    NSParameterAssert(result == 0 && sampleBuffer != NULL);
    if (_previousPixelBuffer) {
        CFRelease(_previousPixelBuffer);
    }
    if (videoInfo) {
        CFRelease(videoInfo);
    }
    
    CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, YES);
    CFMutableDictionaryRef dict = (CFMutableDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);
    CFDictionarySetValue(dict, kCMSampleAttachmentKey_DisplayImmediately, kCFBooleanTrue);
    return CFAutorelease(sampleBuffer);
}

4. 編碼前輸入CMSampleBufferRef组贺， 編碼后輸出 CVPixelBufferRef

//AVCaptureVideoDataOutputSampleBufferDelegate,AVCaptureAudioDataOutputSampleBufferDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
}

// 解碼回調(diào)函數(shù)
static void didDecompress( void *decompressionOutputRefCon, void *sourceFrameRefCon, OSStatus status, VTDecodeInfoFlags infoFlags, CVImageBufferRef pixelBuffer, CMTime presentationTimeStamp, CMTime presentationDuration ){
    CVPixelBufferRef *outputPixelBuffer = (CVPixelBufferRef *)sourceFrameRefCon;
    *outputPixelBuffer = CVPixelBufferRetain(pixelBuffer);
    VideoH264Decoder *decoder = (__bridge VideoH264Decoder *)decompressionOutputRefCon;
    
    if ([decoder.delegate respondsToSelector:@selector(decoder:didDecodingFrame:)]) {
        [decoder.delegate decoder: decoder didDecodingFrame:pixelBuffer];
    }
}

5. CVOpenGLESTextureCacheCreateTextureFromImage生成紋理

CVOpenGLESTextureCacheCreateTextureFromImage ->CVImageBufferRef->Texture
CVOpenGLESTextureCacheCreateTextureFromImage -> CVPixelBufferRef->Texture
CVOpenGLESTextureCacheCreateTextureFromImage -> CMSampleBufferRef-> CVPixelBufferRef ->Texture

CVImageBufferRef==CVPixelBufferRef等價(jià)
CVPixelBufferRef-> Texture-> OpenGL ES 或 Metal渲染
CMSampleBufferRef->Texture-> OpenGL ES 或 Metal渲染

CIImage * ciImage = [CIImage imageWithCVImageBuffer:pixelBuffer];
CIContext * context = [CIContext contextWithOptions:nil];
CGImageRef cgImage = [context createCGImage:ciImage fromRect:CGRectMake(0, 0, 100, 100)];
UIImage * uiImage = [[UIImage alloc] initWithCIImage:ciImage];
UIImage * uiImage2 = [[UIImage alloc] initWithCGImage:cgImage];