CMSampleBufferGetImageBuffer返回null

Question

我正在尝试从CMSampleBufferRef中检索CVPixelBufferRef，以便改变CVPixelBufferRef以动态覆盖水印。

我正在使用CMSampleBufferGetImageBuffer(sampleBuffer)来实现这一目标。我正在打印返回的CVPixelBufferRef的结果，但它始终为null。

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {

    CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

    NSLog(@"PixelBuffer %@",pixelBuffer);
...

}

我有什么我想念的吗？

Answer 1

经过数小时的调试后，结果可能是视频或音频样本。因此，尝试从音频缓冲区获取CVPixelBufferRef将返回null。

我在继续之前通过检查样本类型来解决它。由于我对音频样本不感兴趣，所以我只是在它的音频样本时返回。

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {

    CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

    CMFormatDescriptionRef formatDesc = CMSampleBufferGetFormatDescription(sampleBuffer);
    CMMediaType mediaType = CMFormatDescriptionGetMediaType(formatDesc);

    //Checking sample type before proceeding
    if (mediaType == kCMMediaType_Audio)
    {return;}

//Processing the sample...

}

Answer 2

巴塞尔JD在Swift 4.0中的回答。只是对我有用

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {

    guard let formatDescription: CMFormatDescription = CMSampleBufferGetFormatDescription(sampleBuffer) else { return }

    let mediaType: CMMediaType = CMFormatDescriptionGetMediaType(formatDescription)

    if mediaType == kCMMediaType_Audio {
        print("this was an audio sample....")
        return
    }

}