iOS 从摄像头获取YUV420SP数据

需要引入两个库

#import <AVFoundation/AVFoundation.h>

#import <AssetsLibrary/AssetsLibrary.h>

所在类需遵守AVCaptureVideoDataOutputSampleBufferDelegate代理

设置Session

<span style="font-size:18px;">- (void)setSession
{
_captureInput = [[AVCaptureDeviceInput alloc]initWithDevice:[self getFrontCameraDevice] error:nil];
AVCaptureVideoDataOutput *captureOutput = [[AVCaptureVideoDataOutput alloc]
init];
captureOutput.alwaysDiscardsLateVideoFrames = YES;

dispatch_queue_t queue;
queue = dispatch_queue_create("cameraQueue", NULL);
[captureOutput setSampleBufferDelegate:self queue:queue];
NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
NSNumber* value = [NSNumber
numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange];
NSDictionary* videoSettings = [NSDictionary
dictionaryWithObject:value forKey:key];
[captureOutput setVideoSettings:videoSettings];
self.captureSession = [[AVCaptureSession alloc] init];
[self.captureSession addInput:_captureInput];
[self.captureSession addOutput:captureOutput];
[self.captureSession setSessionPreset:AVCaptureSessionPreset640x480];

}</span>

NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange];
表示设置摄像头返回的数据类型为YUV420SP类型

[self.captureSessionsetSessionPreset:AVCaptureSessionPreset640x480];
设置分辨率

<span style="font-size:18px;">/**
*  获取前置摄像头
*
*  @return 摄像头设备
*/
- (AVCaptureDevice *)getFrontCameraDevice{
NSArray *cameras= [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
for (AVCaptureDevice *camera in cameras) {
if ([camera position] == AVCaptureDevicePositionFront) {
return camera;
}
}
return nil;
}</span>

AVCaptureVideoDataOutputSampleBufferDelegate代理中的操作

<span style="font-size:18px;">#pragma mark AVCaptureSession - delegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection {
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

// Lock the base address of the pixel buffer
CVPixelBufferLockBaseAddress(imageBuffer, 0);
CMTime pts = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
CMTime duration = CMSampleBufferGetDuration(sampleBuffer);
// Get the number of bytes per row for the plane pixel buffer
void *imageAddress = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0);

size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);

Byte *buf = malloc(width * height * 3/ 2);
memcpy(buf, imageAddress, width * height);
size_t a = width * height;
size_t b = width * height * 5 / 4;
for (NSInteger i = 0; i < width * height/ 2; i ++) {
memcpy(buf + a, imageAddress + width * height + i , 1);
a++;
i++;
memcpy(buf + b, imageAddress + width * height + i, 1);
b++;

}
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
}</span>

将YUV420SP的数据重新排列为YUV420P

    Byte *buf =
malloc(width * height *3/
2);

    memcpy(buf, imageAddress, width * height);

    size_t a = width * height;

    size_t b = width * height *
5 / 4;

    for (NSInteger i =0; i < width * height/
2; i ++) {

        memcpy(buf + a, imageAddress + width * height + i ,1);

        a++;

        i++;

        memcpy(buf + b, imageAddress + width * height + i,1);

        b++;

        

    }

buf中的数据就是YUV420P的数据可以供OpenGL ES显示