AVFoundation: add text to the CMSampleBufferRef video frame
avfoundation, ios, video-capture
Solution
You should refer the CIFunHouse sample from apple, and you may use this api to draw directly to the buffer
`-(void)render:(CIImage *)image toCVPixelBuffer:(CVPixelBufferRef)buffer bounds:(CGRect)r colorSpace:(CGColorSpaceRef)cs`
You can download it here WWDC2013
Create the context
_eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
_ciContext = [CIContext contextWithEAGLContext:_eaglContext options:@{kCIContextWorkingColorSpace : [NSNull null]} ];
Now render the image
CVPixelBufferRef renderedOutputPixelBuffer = NULL;
OSStatus err = CVPixelBufferPoolCreatePixelBuffer(nil, self.pixelBufferAdaptor.pixelBufferPool, &renderedOutputPixelBuffer);
[_ciContext render:filteredImage toCVPixelBuffer:renderedOutputPixelBuffer bounds:[filteredImage extent]
Problem
I'm building an app using AVFoundation. Just before I call `[assetWriterInput appendSampleBuffer:sampleBuffer]` in `- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection`-method. I manipulate the pixels in the sample buffer (using a pixelbuffer to apply an effect). But the client wants me to put in a text (timestamp & framecounter) as well on the frames, but I haven't found a way to do this yet. I tried to convert the samplebuffer to an Image, apply text on the image, and convert the image back to a samplebuffer, but then ``` CMSampleBufferDataIsReady(sampleBuffer) ``` fails. Here are my UIImage category methods: ``` + (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; } ``` And ``` - (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; } ``` Any ideas? EDIT: I changed my code with Tony's answer. (Thank you!) This code works: ``` 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); ```