how to fetch raw YUV420p camera data

问题

I don't know which value to use to fetch raw YUV420p data. code below first:

AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
output.alwaysDiscardsLateVideoFrames = YES;
output.videoSettings = @{(id)kCVPixelBufferPixelFormatTypeKey: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange]};
//output.videoSettings = @{(id)kCVPixelBufferPixelFormatTypeKey: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA]};

dispatch_queue_t queue;
queue = dispatch_queue_create("CameraQueue", NULL);
[output setSampleBufferDelegate:self queue:queue];

[session addOutput:output];

I noticed that kCVPixelFormatType has some values, does somebody know which value is right to fetch raw YUV420p data?

kCVPixelFormatType_420YpCbCr8Planar
kCVPixelFormatType_420YpCbCr8PlanarFullRange
kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange
kCVPixelFormatType_420YpCbCr8BiPlanarFullRange

can be one of them?

回答1:

It depends on which particular YUV420 you want to get: Planar/Biplanar refers to the arrangement of the luma and chroma components in memory, Planar meaning that each component comes in a buffer, contiguous or not, and Biplanar pointing to two buffers, one for luma and another for chroma, usually interleaved. An example of Planar is YUV420 format and an example of Biplanar is NV21 or NV12

VideoRange and FullRange refers to the values of the luma component, Video referring to [16,235] accepted levels and FullRange to [0,255]. This confusing agreement comes from the MPEG standard (see here)...

来源：https://stackoverflow.com/questions/24113392/how-to-fetch-raw-yuv420p-camera-data