Objective c 从IDeckLinkVideoInputFrame创建CVPixelBufferRef

我正在使用BlackMagic DeckLink SDK尝试从BM设备捕获帧

我试图从

DeckLinkController:：VideoInputFrameArrived

回调中的

IDeckLinkVideoInputFrame

中获取像素数据，并将其转换为

CVPixelBufferRef

，以便能够使用AVFoundation的

AvassetWriterInputPixelBufferAdapter

和

AVAssetWriter

将其写入磁盘。除了写入磁盘的所有帧都是绿色的之外，我使用的代码似乎正常工作。（BlackMagic在屏幕上生成预览的示例代码确实显示了一幅图像，因此设备和设备设置应该是正常的）

AVAssetWriter

的设置如下：

writer = [[AVAssetWriter assetWriterWithURL:destinationUrl
                                  fileType:AVFileTypeAppleM4V
                                     error:&error] retain];
if(error)
    NSLog(@"ERROR: %@", [error localizedDescription]);

NSMutableDictionary * outputSettings = [[NSMutableDictionary alloc] init];

[outputSettings setObject: AVVideoCodecH264
                   forKey: AVVideoCodecKey];
[outputSettings setObject: [NSNumber numberWithInt:1920]
                   forKey: AVVideoWidthKey];
[outputSettings setObject: [NSNumber numberWithInt:1080]
                   forKey: AVVideoHeightKey];

NSMutableDictionary * compressionProperties = [[NSMutableDictionary alloc] init];
[compressionProperties setObject: [NSNumber numberWithInt: 1000000]
                          forKey: AVVideoAverageBitRateKey];
[compressionProperties setObject: [NSNumber numberWithInt: 16]
                          forKey: AVVideoMaxKeyFrameIntervalKey];
[compressionProperties setObject: AVVideoProfileLevelH264Main31
                          forKey: AVVideoProfileLevelKey];

[outputSettings setObject: compressionProperties
                   forKey: AVVideoCompressionPropertiesKey];

writerVideoInput = [[AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:outputSettings] retain];

NSMutableDictionary * pixBufSettings = [[NSMutableDictionary alloc] init];

[pixBufSettings setObject: [NSNumber numberWithInt: kCVPixelFormatType_422YpCbCr8_yuvs]
                   forKey: (NSString *) kCVPixelBufferPixelFormatTypeKey];
[pixBufSettings setObject: [NSNumber numberWithInt: 1920]
                   forKey: (NSString *) kCVPixelBufferWidthKey];
[pixBufSettings setObject: [NSNumber numberWithInt: 1080]
                   forKey: (NSString *) kCVPixelBufferHeightKey];

writerVideoInput.expectsMediaDataInRealTime = YES;

writer.shouldOptimizeForNetworkUse = NO;

adaptor = [[AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerVideoInput
                                                                           sourcePixelBufferAttributes:pixBufSettings] retain];
[writer addInput:writerVideoInput];

void *videoData;
int64_t frameTime;
int64_t frameDuration;

videoFrame->GetBytes(&videoData);
videoFrame->GetStreamTime(&frameTime, &frameDuration, 3000);

CMTime presentationTime = CMTimeMake(frameDuration, 3000);

CVPixelBufferRef buffer = NULL;

CVPixelBufferPoolCreatePixelBuffer(NULL, adaptor.pixelBufferPool, &buffer);
CVPixelBufferLockBaseAddress(buffer, 0);

void *rasterData = CVPixelBufferGetBaseAddress(buffer);
memcpy(rasterData, videoData, (videoFrame->GetRowBytes()*videoFrame->GetHeight()));

CVPixelBufferUnlockBaseAddress(buffer, 0);

if (buffer)
{
    if(![adaptor appendPixelBuffer:buffer withPresentationTime:presentationTime]) {
        NSLog(@"ERROR appending pixelbuffer: %@", writer.error);
        [writerVideoInput markAsFinished];
        if(![writer finishWriting])
            NSLog(@"ERROR finishing writing: %@", [writer.error localizedDescription]);
    }
    else {
        NSLog(@"SUCCESS");
        if(buffer)
            CVPixelBufferRelease(buffer);
    }
}

作为参考，这些输出设置和压缩选项应该是正确的，但我尝试了几种不同的选择

当一帧从设备进入时，我将其转换为

CVPixelBufferRef

，如下所示：

writer = [[AVAssetWriter assetWriterWithURL:destinationUrl
                                  fileType:AVFileTypeAppleM4V
                                     error:&error] retain];
if(error)
    NSLog(@"ERROR: %@", [error localizedDescription]);

NSMutableDictionary * outputSettings = [[NSMutableDictionary alloc] init];

[outputSettings setObject: AVVideoCodecH264
                   forKey: AVVideoCodecKey];
[outputSettings setObject: [NSNumber numberWithInt:1920]
                   forKey: AVVideoWidthKey];
[outputSettings setObject: [NSNumber numberWithInt:1080]
                   forKey: AVVideoHeightKey];

NSMutableDictionary * compressionProperties = [[NSMutableDictionary alloc] init];
[compressionProperties setObject: [NSNumber numberWithInt: 1000000]
                          forKey: AVVideoAverageBitRateKey];
[compressionProperties setObject: [NSNumber numberWithInt: 16]
                          forKey: AVVideoMaxKeyFrameIntervalKey];
[compressionProperties setObject: AVVideoProfileLevelH264Main31
                          forKey: AVVideoProfileLevelKey];

[outputSettings setObject: compressionProperties
                   forKey: AVVideoCompressionPropertiesKey];

writerVideoInput = [[AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:outputSettings] retain];

NSMutableDictionary * pixBufSettings = [[NSMutableDictionary alloc] init];

[pixBufSettings setObject: [NSNumber numberWithInt: kCVPixelFormatType_422YpCbCr8_yuvs]
                   forKey: (NSString *) kCVPixelBufferPixelFormatTypeKey];
[pixBufSettings setObject: [NSNumber numberWithInt: 1920]
                   forKey: (NSString *) kCVPixelBufferWidthKey];
[pixBufSettings setObject: [NSNumber numberWithInt: 1080]
                   forKey: (NSString *) kCVPixelBufferHeightKey];

writerVideoInput.expectsMediaDataInRealTime = YES;

writer.shouldOptimizeForNetworkUse = NO;

adaptor = [[AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerVideoInput
                                                                           sourcePixelBufferAttributes:pixBufSettings] retain];
[writer addInput:writerVideoInput];

void *videoData;
int64_t frameTime;
int64_t frameDuration;

videoFrame->GetBytes(&videoData);
videoFrame->GetStreamTime(&frameTime, &frameDuration, 3000);

CMTime presentationTime = CMTimeMake(frameDuration, 3000);

CVPixelBufferRef buffer = NULL;

CVPixelBufferPoolCreatePixelBuffer(NULL, adaptor.pixelBufferPool, &buffer);
CVPixelBufferLockBaseAddress(buffer, 0);

void *rasterData = CVPixelBufferGetBaseAddress(buffer);
memcpy(rasterData, videoData, (videoFrame->GetRowBytes()*videoFrame->GetHeight()));

CVPixelBufferUnlockBaseAddress(buffer, 0);

if (buffer)
{
    if(![adaptor appendPixelBuffer:buffer withPresentationTime:presentationTime]) {
        NSLog(@"ERROR appending pixelbuffer: %@", writer.error);
        [writerVideoInput markAsFinished];
        if(![writer finishWriting])
            NSLog(@"ERROR finishing writing: %@", [writer.error localizedDescription]);
    }
    else {
        NSLog(@"SUCCESS");
        if(buffer)
            CVPixelBufferRelease(buffer);
    }
}

此代码将帧附加到AvassetWriterInputPixelBufferAdapter，但所有帧都是绿色的

---

有人知道我做错了什么吗？或者有人有使用BlackMagic Decklink SDK使用AVFoundation捕获和压缩帧的经验吗

当您看到“绿色”并在YUV颜色空间中工作时，您会看到缓冲区中的值为0。由于AVWriter正在写入帧，“缓冲区”包含的值很可能为0。我认为有几种方法可以实现

1） 您要附加的缓冲区很可能已用0初始化，因此您的复制可能失败。在代码中，如果（videoFrame->GetRowBytes（）*videoFrame->GetHeight（））的计算结果为0，则可能会发生这种情况。这似乎不可能，但我会检查一下

2） CVPixelBufferGetBaseAddress要么返回错误的指针，要么PixelBuffer本身的格式错误，要么可能无效（但由于API中的保护措施，没有崩溃）

3） 不管出于什么原因，“视频数据”本身就充满了0。DeckLinkCaptureDelegate在不喜欢输入格式时返回的帧中没有任何内容（通常这是因为传递给EnableVideoInput的BMDDisplayMode与您的视频源不匹配）

int flags=videoFrame->GetFlags();
if (flags & bmdFrameHasNoInputSource)
{
    //our input format doesn't match the source
}

除了更改源模式并重试之外，快速检查是将memcpy行更改为以下内容：

memset(rasterData, 0x3f, 1920*1080*2);

如果仍然看到绿色帧，请仔细查看#2。如果看到不同颜色的帧，则问题是#1或#3，并且很可能视频输入的分辨率与您选择的BMDDisplay模式不匹配

还有一件事需要注意。我认为您创建演示时间的行是错误的。它可能应该是（注意将frameDuration更改为frameTime:

CMTime presentationTime = CMTimeMake(frameTime, 3000);