iOS RTMP 视频直播开发笔记（1）----- 采集摄像头图像

这里简单说下 iOS 的摄像头采集。

首先初始化AVCaptureSession，说到Session，有没有人想到AVAudioSession呢？

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// 初始化 AVCaptureSession

_session = [[AVCaptureSession alloc] init];

设置采集的 Video 和 Audio 格式，这两个是分开设置的，也就是说，你可以只采集视频。

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// 配置采集输入源（摄像头）

NSError*error=nil;

// 获得一个采集设备，例如前置/后置摄像头

AVCaptureDevice*videoDevice=[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

// 用设备初始化一个采集的输入对象

AVCaptureDeviceInput*videoInput=[AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];

if(error){

    NSLog(@"Error getting video input device: %@",error.description);

}

if([_session canAddInput:videoInput]){

    [_session addInput:videoInput];// 添加到Session

}

 

// 配置采集输出，即我们取得视频图像的接口

_videoQueue=dispatch_queue_create("Video Capture Queue",DISPATCH_QUEUE_SERIAL);

_videoOutput=[[AVCaptureVideoDataOutputalloc] init];

[_videoOutput setSampleBufferDelegate:self queue:_videoQueue];

 

// 配置输出视频图像格式

NSDictionary*captureSettings=@{(NSString*)kCVPixelBufferPixelFormatTypeKey:@(kCVPixelFormatType_32BGRA)};

 

_videoOutput.videoSettings=captureSettings;

_videoOutput.alwaysDiscardsLateVideoFrames=YES;

if([_session canAddOutput:_videoOutput]){

    [_session addOutput:_videoOutput];  // 添加到Session

}

 

// 保存Connection，用于在SampleBufferDelegate中判断数据来源（是Video/Audio？）

_videoConnection=[_videoOutput connectionWithMediaType:AVMediaTypeVideo];

实现 AVCaptureOutputDelegate：

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- (void) captureOutput:(AVCaptureOutput *)captureOutput

didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer

        fromConnection:(AVCaptureConnection *)connection

{

    // 这里的sampleBuffer就是采集到的数据了，但它是Video还是Audio的数据，得根据connection来判断

    if (connection == _videoConnection) {  // Video

        /*

        // 取得当前视频尺寸信息

        CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

        int width = CVPixelBufferGetWidth(pixelBuffer);

        int height = CVPixelBufferGetHeight(pixelBuffer);

        NSLog(@"video width: %d  height: %d", width, height);

        */

         NSLog(@"在这里获得video sampleBuffer，做进一步处理（编码H.264）");

    } else if (connection == _audioConnection) {  // Audio

        NSLog(@"这里获得audio sampleBuffer，做进一步处理（编码AAC）");

    }

}

关于实时编码H.264和AAC Buffer，这里又是两个技术点，之后再讲吧。

配置完成，现在启动 Session：

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// 启动 Session

[_sessionstartRunning];

1.1 附加任务：将当前硬件采集视频图像显示到屏幕

很简单，发送端直接使用自家的AVCaptureVideoPreviewLayer显示，so easy

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_previewLayer=[AVCaptureVideoPreviewLayer layerWithSession:_session];

_previewLayer.videoGravity=AVLayerVideoGravityResizeAspectFill;// 设置预览时的视频缩放方式

[[_previewLayerconnection] setVideoOrientation:AVCaptureVideoOrientationPortrait];// 设置视频的朝向

 

_previewLayer.frame=self.view.layer.bounds;

[self.view.layer addSublayer:_previewLayer];

然后将这个layer添加到界面中即可显示了。

具体实现代码：

#import "MyAVController.h"

#import <AVFoundation/AVFoundation.h>

#import <CoreGraphics/CoreGraphics.h>

#import <CoreVideo/CoreVideo.h>

#import <CoreMedia/CoreMedia.h>

@interface MyAVController()<AVCaptureVideoDataOutputSampleBufferDelegate>

@property (nonatomic,retain) AVCaptureSession *captureSession;

@property (nonatomic,retain) UIImageView *imageView;

@property (nonatomic,retain) CALayer *customLayer;

@property (nonatomic,retain) AVCaptureVideoPreviewLayer *prevLayer;

- (void)initCapture;

@end

#import "MyAVController.h"

@implementation MyAVController

{

    AVCaptureSession *_captureSession;

    UIImageView *_imageView;

    CALayer *_customLayer;

    AVCaptureVideoPreviewLayer *_prevLayer;

    AVCaptureConnection *_videoConnection;

    AVCaptureConnection *_audioConnection;

}

#pragma mark -

#pragma mark Initialization

- (id)init {

    self = [superinit];

    if (self) {

        self.imageView =nil;

        self.prevLayer =nil;

        self.customLayer =nil;

    }

    returnself;

}

- (void)viewDidLoad {

    [selfinitCapture];

}

- (void)initCapture {

    //配置采集输入源（摄像头）

    AVCaptureDevice*videoDevice=[AVCaptureDevicedefaultDeviceWithMediaType:AVMediaTypeVideo];

    //用设备初始化一个采集的输入对象

    AVCaptureDeviceInput *captureInput = [AVCaptureDeviceInputdeviceInputWithDevice:videoDevice error:nil];

    AVCaptureVideoDataOutput *captureOutput = [[AVCaptureVideoDataOutputalloc]init];

    captureOutput.alwaysDiscardsLateVideoFrames =YES;

    //captureOutput.minFrameDuration = CMTimeMake(1, 10);

    

    //配置采集输出，即我们取得视频图像的接口

    dispatch_queue_t queue;

    queue = dispatch_queue_create("cameraQueue",NULL);

    

    [captureOutput setSampleBufferDelegate:selfqueue:queue];

    dispatch_release(queue);

    NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;

    //配置输出视频图像格式

    NSNumber* value = [NSNumbernumberWithUnsignedInt:kCVPixelFormatType_32BGRA];

    NSDictionary* videoSettings = [NSDictionary

                                   dictionaryWithObject:valueforKey:key];

    [captureOutput setVideoSettings:videoSettings];

    self.captureSession = [[AVCaptureSessionalloc] init];

    [self.captureSessionaddInput:captureInput];

    [self.captureSessionaddOutput:captureOutput];

    [self.captureSessionstartRunning];

    

    //保存Connection，用于在SampleBufferDelegate中判断数据来源（是Video/Audio？）

    _videoConnection=[captureOutput

                      connectionWithMediaType:AVMediaTypeVideo];

    

    //view

    self.customLayer = [CALayerlayer];

    self.customLayer.frame =self.view.bounds;

    self.customLayer.transform = CATransform3DRotate(

                                                     CATransform3DIdentity,M_PI/2.0f,0, 0,1);

    self.customLayer.contentsGravity = kCAGravityResizeAspectFill;

    [self.view.layeraddSublayer:self.customLayer];

    self.imageView = [[UIImageViewalloc] init];

    self.imageView.frame =CGRectMake(0,0, 100,100);

    [self.viewaddSubview:self.imageView];

    self.prevLayer = [AVCaptureVideoPreviewLayer

                      layerWithSession:self.captureSession];

    self.prevLayer.frame =CGRectMake(100,0, 100,100);

    self.prevLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    [self.view.layeraddSublayer: self.prevLayer];

}

#pragma mark -

#pragma mark AVCaptureSession delegate

- (void)captureOutput:(AVCaptureOutput *)captureOutput

didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer

       fromConnection:(AVCaptureConnection *)connection

{

    

    // 这里的sampleBuffer就是采集到的数据了，但它是Video还是Audio的数据，得根据connection来判断

    if (connection ==_videoConnection) {  // Video

        /*

         // 取得当前视频尺寸信息

         CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

         int width = CVPixelBufferGetWidth(pixelBuffer);

         int height = CVPixelBufferGetHeight(pixelBuffer);

         NSLog(@"video width: %d  height: %d", width, height);

         */

        NSLog(@"在这里获得video sampleBuffer，做进一步处理（编码H.264）");

    } elseif (connection == _audioConnection) {  // Audio

        NSLog(@"这里获得audio sampleBuffer，做进一步处理（编码AAC）");

    }

    

    

    

    NSAutoreleasePool * pool = [[NSAutoreleasePoolalloc] init];

    // 这里的sampleBuffer就是采集到的数据了，但它是Video还是Audio的数据，得根据connection来判断

    CVImageBufferRef imageBuffer =CMSampleBufferGetImageBuffer(sampleBuffer);

    CVPixelBufferLockBaseAddress(imageBuffer,0);

    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);

    size_t bytesPerRow =CVPixelBufferGetBytesPerRow(imageBuffer);

    size_t width =CVPixelBufferGetWidth(imageBuffer);

    size_t height =CVPixelBufferGetHeight(imageBuffer);

    

    CGColorSpaceRef colorSpace =CGColorSpaceCreateDeviceRGB();

    CGContextRef newContext =CGBitmapContextCreate(baseAddress,

                                                    width, height,8, bytesPerRow, colorSpace,

                                                    kCGBitmapByteOrder32Little |kCGImageAlphaPremultipliedFirst);

    CGImageRef newImage =CGBitmapContextCreateImage(newContext);

    

    CGContextRelease(newContext);

    CGColorSpaceRelease(colorSpace);

    

    [self.customLayerperformSelectorOnMainThread:@selector(setContents:)

                                       withObject: (__bridgeid) newImage waitUntilDone:YES];

    

    UIImage *image= [UIImageimageWithCGImage:newImagescale:1.0

                                  orientation:UIImageOrientationRight];

    

    CGImageRelease(newImage);

    

    [self.imageViewperformSelectorOnMainThread:@selector(setImage:)

                                     withObject:imagewaitUntilDone:YES];

    

    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    

    [pool drain];

}

#pragma mark -

#pragma mark Memory management

- (void)viewDidUnload {

    self.imageView =nil;

    self.customLayer =nil;

    self.prevLayer =nil;

}

- (void)dealloc {

    [self.captureSessionrelease];

    [superdealloc];

}

@end