我是 iOS 编程和多媒体的新手,我正在浏览苹果在此链接上提供的名为 RosyWriter 的示例项目。在这里我看到在代码中有一个函数captureOutput:didOutputSampleBuffer:fromConnection
在下面给出的代码中命名:
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer);
if ( connection == videoConnection ) {
// Get framerate
CMTime timestamp = CMSampleBufferGetPresentationTimeStamp( sampleBuffer );
[self calculateFramerateAtTimestamp:timestamp];
// Get frame dimensions (for onscreen display)
if (self.videoDimensions.width == 0 && self.videoDimensions.height == 0)
self.videoDimensions = CMVideoFormatDescriptionGetDimensions( formatDescription );
// Get buffer type
if ( self.videoType == 0 )
self.videoType = CMFormatDescriptionGetMediaSubType( formatDescription );
CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
// Synchronously process the pixel buffer to de-green it.
[self processPixelBuffer:pixelBuffer];
// Enqueue it for preview. This is a shallow queue, so if image processing is taking too long,
// we'll drop this frame for preview (this keeps preview latency low).
OSStatus err = CMBufferQueueEnqueue(previewBufferQueue, sampleBuffer);
if ( !err ) {
dispatch_async(dispatch_get_main_queue(), ^{
CMSampleBufferRef sbuf = (CMSampleBufferRef)CMBufferQueueDequeueAndRetain(previewBufferQueue);
if (sbuf) {
CVImageBufferRef pixBuf = CMSampleBufferGetImageBuffer(sbuf);
[self.delegate pixelBufferReadyForDisplay:pixBuf];
CFRelease(sbuf);
}
});
}
}
CFRetain(sampleBuffer);
CFRetain(formatDescription);
dispatch_async(movieWritingQueue, ^{
if ( assetWriter ) {
BOOL wasReadyToRecord = (readyToRecordAudio && readyToRecordVideo);
if (connection == videoConnection) {
// Initialize the video input if this is not done yet
if (!readyToRecordVideo)
readyToRecordVideo = [self setupAssetWriterVideoInput:formatDescription];
// Write video data to file
if (readyToRecordVideo && readyToRecordAudio)
[self writeSampleBuffer:sampleBuffer ofType:AVMediaTypeVideo];
}
else if (connection == audioConnection) {
// Initialize the audio input if this is not done yet
if (!readyToRecordAudio)
readyToRecordAudio = [self setupAssetWriterAudioInput:formatDescription];
// Write audio data to file
if (readyToRecordAudio && readyToRecordVideo)
[self writeSampleBuffer:sampleBuffer ofType:AVMediaTypeAudio];
}
BOOL isReadyToRecord = (readyToRecordAudio && readyToRecordVideo);
if ( !wasReadyToRecord && isReadyToRecord ) {
recordingWillBeStarted = NO;
self.recording = YES;
[self.delegate recordingDidStart];
}
}
CFRelease(sampleBuffer);
CFRelease(formatDescription);
});
}
这里调用了一个名为的函数pixelBufferReadyForDisplay
,它需要一个类型的参数CVPixelBufferRef
pixelBufferReadyForDisplay 原型
- (void)pixelBufferReadyForDisplay:(CVPixelBufferRef)pixelBuffer;
但是在上面的代码中,当调用这个函数时,它传递了pixBuf
类型为的变量CVImageBufferRef
所以我的问题是,是否需要使用任何函数或类型转换将 CVImageBufferRef 转换为 CVPixelBufferRef 或者这是由编译器隐式完成的?
谢谢。