AVFoundation：将文本添加到CMSampleBufferRefvideo帧

我正在使用AVFoundation构build一个应用程序。

就在我调用[assetWriterInput appendSampleBuffer:sampleBuffer] - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection – 方法。

我操纵样本缓冲区中的像素（使用像素缓冲区来应用效果）。

但是客户希望我在框架中input文本（时间戳和帧计数器），但是我还没有find一种方法来完成这个任务。

我试图将samplebuffer转换成图像，在图像上应用文本，然后将图像转换回采样缓冲区，但是

 CMSampleBufferDataIsReady(sampleBuffer) 

失败。

这里是我的UIImage类别的方法：

  + (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer { CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); CVPixelBufferLockBaseAddress(imageBuffer,0); uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer); size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); size_t width = CVPixelBufferGetWidth(imageBuffer); size_t height = CVPixelBufferGetHeight(imageBuffer); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); CGImageRef newImage = CGBitmapContextCreateImage(newContext); CGContextRelease(newContext); CGColorSpaceRelease(colorSpace); UIImage *newUIImage = [UIImage imageWithCGImage:newImage]; CFRelease(newImage); return newUIImage; } 

和

  - (CMSampleBufferRef) cmSampleBuffer { CGImageRef image = self.CGImage; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey, [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey, nil]; CVPixelBufferRef pxbuffer = NULL; CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, self.size.width, self.size.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options, &pxbuffer); NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL); CVPixelBufferLockBaseAddress(pxbuffer, 0); void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer); NSParameterAssert(pxdata != NULL); CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef context = CGBitmapContextCreate(pxdata, self.size.width, self.size.height, 8, 4*self.size.width, rgbColorSpace, kCGImageAlphaNoneSkipFirst); NSParameterAssert(context); CGContextConcatCTM(context, CGAffineTransformMakeRotation(0)); CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image)), image); CGColorSpaceRelease(rgbColorSpace); CGContextRelease(context); CVPixelBufferUnlockBaseAddress(pxbuffer, 0); CMVideoFormatDescriptionRef videoInfo = NULL; CMSampleBufferRef sampleBuffer = NULL; CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, pxbuffer, true, NULL, NULL, videoInfo, NULL, &sampleBuffer); return sampleBuffer; } 

有任何想法吗？

编辑：

我用Tony的答案改变了我的代码。 （谢谢！）这段代码的作品：

 CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); CVPixelBufferLockBaseAddress( pixelBuffer, 0 ); EAGLContext *eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2]; CIContext *ciContext = [CIContext contextWithEAGLContext:eaglContext options:@{kCIContextWorkingColorSpace : [NSNull null]} ]; UIFont *font = [UIFont fontWithName:@"Helvetica" size:40]; NSDictionary *attributes = @{NSFontAttributeName: font, NSForegroundColorAttributeName: [UIColor lightTextColor]}; UIImage *img = [UIImage imageFromText:@"01 - 13/02/2014 15:18:21:654" withAttributes:attributes]; CIImage *filteredImage = [[CIImage alloc] initWithCGImage:img.CGImage]; [ciContext render:filteredImage toCVPixelBuffer:pixelBuffer bounds:[filteredImage extent] colorSpace:CGColorSpaceCreateDeviceRGB()]; CVPixelBufferUnlockBaseAddress(pixelBuffer, 0); 

Answer 1

你应该参考苹果公司的CIFunHouse样本，你可以使用这个API直接绘制到缓冲区

-(void)render:(CIImage *)image toCVPixelBuffer:(CVPixelBufferRef)buffer bounds:(CGRect)r colorSpace:(CGColorSpaceRef)cs

你可以在这里下载WWDC2013

创build上下文

 _eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2]; _ciContext = [CIContext contextWithEAGLContext:_eaglContext options:@{kCIContextWorkingColorSpace : [NSNull null]} ]; 

现在渲染图像

 CVPixelBufferRef renderedOutputPixelBuffer = NULL; OSStatus err = CVPixelBufferPoolCreatePixelBuffer(nil, self.pixelBufferAdaptor.pixelBufferPool, &renderedOutputPixelBuffer); [_ciContext render:filteredImage toCVPixelBuffer:renderedOutputPixelBuffer bounds:[filteredImage extent]