How do I convert a CGImage to CMSampleBufferRef?
avfoundation, core-media, core-video, ios
Solution
Aha, I’ve completely missed the `AVAssetWriterInputPixelBufferAdaptor` class that’s made especially for piping the pixel buffers into a writer input. Now the code works, even without the messy `CMSampleBuffer` stuff.
Problem
I’d like to convert a `CGImage` to `CMSampleBufferRef` and append it to a `AVAssetWriterInput` using the `appendSampleBuffer:` method. I’ve managed to get the `CMSampleBufferRef` using the following code, but the `appendSampleBuffer:` simply returns `NO` when I supply the resulting `CMSampleBufferRef`. What am I doing wrong? ``` - (void) appendCGImage: (CGImageRef) frame { const int width = CGImageGetWidth(frame); const int height = CGImageGetHeight(frame); // Create a dummy pixel buffer to try the encoding // on something simple. CVPixelBufferRef pixelBuffer = NULL; CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, width, height, kCVPixelFormatType_32BGRA, NULL, &pixelBuffer); NSParameterAssert(status == kCVReturnSuccess && pixelBuffer != NULL); // Sample timing info. CMTime frameTime = CMTimeMake(1, 30); CMTime currentTime = CMTimeAdd(lastSampleTime, frameTime); CMSampleTimingInfo timing = {frameTime, currentTime, kCMTimeInvalid}; OSStatus result = 0; // Sample format. CMVideoFormatDescriptionRef videoInfo = NULL; result = CMVideoFormatDescriptionCreateForImageBuffer(NULL, pixelBuffer, &videoInfo); NSParameterAssert(result == 0 && videoInfo != NULL); // Create sample buffer. CMSampleBufferRef sampleBuffer = NULL; result = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, true, NULL, NULL, videoInfo, &timing, &sampleBuffer); NSParameterAssert(result == 0 && sampleBuffer != NULL); // Ship out the frame. NSParameterAssert(CMSampleBufferDataIsReady(sampleBuffer)); NSParameterAssert([writerInput isReadyForMoreMediaData]); BOOL success = [writerInput appendSampleBuffer:frame]; NSParameterAssert(success); // no go :( } ``` P.S. I know there are memory leaks in this code, I’ve omitted some of the code for simplicity.