objective-c – 使用CGDisplayStream编码H.264压缩会话

发布时间：2020-12-16 06:53:14 所属栏目：百科来源：网络整理

导读：我正在尝试使用屏幕上的数据创建一个H.264压缩会话.我已经创建了一个CGDisplayStreamRef实例,如下所示： displayStream = CGDisplayStreamCreateWithDispatchQueue(0,100,k32BGRAPixelFormat,nil,self.screenCaptureQueue,^(CGDisplayStreamFrameStatus stat

我正在尝试使用屏幕上的数据创建一个H.264压缩会话.我已经创建了一个CGDisplayStreamRef实例,如下所示：

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

以下是我目前如何设置编码功能：

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

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

我试图了解如何将数据从我的屏幕转换为CMSampleBufferRef,以便我可以正确调用我的编码功能.到目前为止,我还无法确定这是否可行,或者是我正在尝试做的正确方法.有没有人有什么建议？

编辑：我已经将我的IOSurface转换为CMBlockBuffer,但尚未弄清楚如何将其转换为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,&blockBuffer);

编辑2

更进一步：

CMSampleBufferRef *sampleBuffer;

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

[self encode:*sampleBuffer];

解决方法

可能,我有点迟了但是,它可能对其他人有帮助：

CGDisplayStreamCreateWithDispatchQueue(CGMainDisplayID(),CGDisplayStreamUpdateRef updateRef) {
    // The created pixel buffer retains the surface object.
    CVPixelBufferRef pixelBuffer;
    CVPixelBufferCreateWithIOSurface(NULL,frameSurface,&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,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);
});

（编辑：李大同）

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