Encoding a H.264 Compression Session Using CGDisplayStream

Question

I am trying to create an H.264 compression session with data from my screen. I created an instance CGDisplayStreamRef, for example:

displayStream = CGDisplayStreamCreateWithDispatchQueue(0, 100, 100, k32BGRAPixelFormat, nil, self.screenCaptureQueue, ^(CGDisplayStreamFrameStatus status, uint64_t displayTime, IOSurfaceRef frameSurface, CGDisplayStreamUpdateRef updateRef) {
    //Call encoding session here
});

The following is how I currently have the encoding function installed:

- (void) encode:(CMSampleBufferRef )sampleBuffer {
    CVImageBufferRef imageBuffer = (CVImageBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);
    CMTime presentationTimeStamp = CMTimeMake(frameID++, 1000);
    VTEncodeInfoFlags flags;
    OSStatus statusCode = VTCompressionSessionEncodeFrame(EncodingSession,
                                                          imageBuffer,
                                                          presentationTimeStamp,
                                                          kCMTimeInvalid,
                                                          NULL, NULL, &flags);
    if (statusCode != noErr) {
        NSLog(@"H264: VTCompressionSessionEncodeFrame failed with %d", (int)statusCode);

        VTCompressionSessionInvalidate(EncodingSession);
        CFRelease(EncodingSession);
        EncodingSession = NULL;
        return;
    }
    NSLog(@"H264: VTCompressionSessionEncodeFrame Success");
}

I am trying to understand how I can convert data from my screen to CMSampleBufferRefso that I can correctly call the encoding function. So far I have not been able to determine if this is possible, or the correct approach to what I am trying to do. Anyone have any suggestions?

EDIT : I got IOSurfaceconverted to CMBlockBuffer, but haven't figured out how to convert it to CMSampleBufferRef:

void *mem = IOSurfaceGetBaseAddress(frameSurface);
size_t bytesPerRow = IOSurfaceGetBytesPerRow(frameSurface);
size_t height = IOSurfaceGetHeight(frameSurface);
size_t totalBytes = bytesPerRow * height;

CMBlockBufferRef blockBuffer;

CMBlockBufferCreateWithMemoryBlock(kCFAllocatorNull, mem, totalBytes, kCFAllocatorNull, NULL, 0, totalBytes, 0, &blockBuffer);

EDIT 2

Further progress:

CMSampleBufferRef *sampleBuffer;

OSStatus sampleStatus = CMSampleBufferCreate(
                             NULL, blockBuffer, TRUE, NULL, NULL,
                             NULL, 1, 1, NULL,
                             0, NULL, sampleBuffer);

[self encode:*sampleBuffer];

Answer 1

, , , , :

CGDisplayStreamCreateWithDispatchQueue(CGMainDisplayID(), 100, 100, k32BGRAPixelFormat, nil, self.screenCaptureQueue, ^(CGDisplayStreamFrameStatus status, uint64_t displayTime, IOSurfaceRef frameSurface, CGDisplayStreamUpdateRef updateRef) {
    // The created pixel buffer retains the surface object.
    CVPixelBufferRef pixelBuffer;
    CVPixelBufferCreateWithIOSurface(NULL, frameSurface, NULL, &pixelBuffer);

    // Create the video-type-specific description for the pixel buffer.
    CMVideoFormatDescriptionRef videoFormatDescription;
    CMVideoFormatDescriptionCreateForImageBuffer(NULL, pixelBuffer, &videoFormatDescription);

    // All the necessary parts for creating a `CMSampleBuffer` are ready.
    CMSampleBufferRef sampleBuffer;
    CMSampleTimingInfo timingInfo;
    CMSampleBufferCreateReadyWithImageBuffer(NULL, pixelBuffer, videoFormatDescription, &timingInfo, &sampleBuffer);

    // Do the stuff

    // Release the resources to let the frame surface be reused in the queue
    // `kCGDisplayStreamQueueDepth` is responsible for the size of the queue 
    CFRelease(sampleBuffer);
    CFRelease(pixelBuffer);
});