本文分享webrtc的ios端上自定义采集视频
本质问题：从摄像机里面取出数据给webrtc模块使用。
建立 RTCCameraVideoCapturer （视频生产者）--->RTCVideoSource(消费者) 之间的通道

头问题 *.h

@property(nonatomic, strong) RTCMediaStream* _Nullable streamLocal; //本地流
@property(nonatomic, strong) RTCCameraVideoCapturer* cameraCapturer; //capture
@property(nonatomic, strong) RTCVideoSource* videoSource;      //数据源头


//methord
-(void) setupLocal；
-(void)startCapture；

实现文件 *.m

-(void) setupLocal
{
        RTCPeerConnectionFactory* factory = [RTCEngine sharedInstance].connectionFactory;
        _streamLocal = [factory mediaStreamWithStreamId:_streamId]; //本地流RTCMediaStream
        _videoSource = [_factory videoSource];//--2--获取数据源头RTCVideoSource
       
        //视频  RTCCameraVideoCapturer
         cameraCapturer = [[RTCCameraVideoCapturer alloc] initWithDelegate:videoFrameConsumer];

       //cameraCapturer = [[RTCCameraVideoCapturer alloc] initWithDelegate:videoSource]; //这里判断需不需要取出webrtc进行进一步处理。美颜，滤镜等处理。具体处理下一个章节详细记录,

         RTCVideoTrack* videoTrack = [factory videoTrackWithSource:videoSource trackId:[[NSUUID UUID] UUIDString]];
          [_streamLocal addVideoTrack:videoTrack];

      //音频
         RTCAudioSource* audioSource = [factory audioSourceWithConstraints:nil];
         RTCVideoTrack*     videoTrack = [factory audioTrackWithSource:audioSource trackId:[[NSUUID UUID] UUIDString]];
        [_streamLocal addAudioTrack:audioTrack];

}

//begin
-(void)startCapture
{
    AVCaptureDevicePosition position =
    usingFrontCamera ? AVCaptureDevicePositionFront : AVCaptureDevicePositionBack;
    AVCaptureDevice *device = [self findDeviceForPosition:position];
    
    AVCaptureDeviceFormat *format = [self selectFormatForDevice:device];
    [cameraCapturer startCaptureWithDevice:device format:format fps:frameRate];
}

//inner methord
- (AVCaptureDevice *)findDeviceForPosition:(AVCaptureDevicePosition)position {
    NSArray<AVCaptureDevice *> *captureDevices = [RTCCameraVideoCapturer captureDevices];
    for (AVCaptureDevice *device in captureDevices) {
        if (device.position == position) {
            return device;
        }
    }
    return captureDevices[0];
}
// 查找最接近采集方案的采集格式
- (AVCaptureDeviceFormat *)selectFormatForDevice:(AVCaptureDevice *)device {
    NSArray<AVCaptureDeviceFormat *> *formats = [RTCCameraVideoCapturer supportedFormatsForDevice:device];
    int targetWidth = (int)minWidth;
    int targetHeight = (int)minHeight;
    AVCaptureDeviceFormat *selectedFormat = nil;
    int currentDiff = INT_MAX;
    for (AVCaptureDeviceFormat *format in formats) {
        CMVideoDimensions dimension = CMVideoFormatDescriptionGetDimensions(format.formatDescription);
        int diff = abs(targetWidth - dimension.width) + abs(targetHeight - dimension.height);
        if (diff < currentDiff) {
            selectedFormat = format;
            currentDiff = diff;
        }
    }
    NSAssert(selectedFormat != nil, @"No suitable capture format found.");
    CMVideoDimensions dimension = CMVideoFormatDescriptionGetDimensions(selectedFormat.formatDescription);
    cameraWidth = dimension.width;
    cameraHeight = dimension.height;
    return selectedFormat;
}

以上是是webrtc采集代码，另外本地需要预览的这个怎么做呢？
//找到对应的
if (stream && stream.videoTracks.count > 0) {
[stream.videoTracks[0] addRenderer:self]; //
}

@interface RTCView() <RTCVideoViewDelegate>
-(void)renderFrame:(RTCVideoFrame *)frame //会在这里回调帧数据，
{
// todo it is hack, need to remove this
if(subview==nil){
return;
}
[subview renderFrame:frame]; //放到渲染的RTCMTLVideoView or RTCEAGLVideoView 即可
}

****补充：RTCVideoFrameConsumer 代码

头问题RTCVideoFrameConsumer.h

#import <Foundation/Foundation.h>

@import WebRTC;

@protocol RTCVideoFrameDelegate <NSObject>

- (void)didGotVideoFrame:(RTCVideoFrame *_Nonnull)frame;

@end

@interface RTCVideoFrameConsumer : NSObject <RTCVideoCapturerDelegate>

@property (nonatomic, weak) id<RTCVideoFrameDelegate> _Nullable delegate;

-(instancetype _Nonnull )initWithDelegate:(id<RTCVideoFrameDelegate>_Nullable)delegate;

@end

RTCVideoFrameConsumer.m

#import "RTCVideoFrameConsumer.h"

@implementation RTCVideoFrameConsumer

-(instancetype)initWithDelegate:(id<RTCVideoFrameDelegate>)delegate
{
    self = [super init];
    _delegate = delegate;
    return self;
}


-(void)capturer:(RTCVideoCapturer *)capturer didCaptureVideoFrame:(RTCVideoFrame *)frame
{
    if (self.delegate != nil && frame != nil) {
        [self.delegate didGotVideoFrame:frame];
    }
}

- (void)dealloc {
    
    
}
@end

本质就是一个代理从 RTCCameraVideoCapturer 获取数据 回调didCaptureVideoFrame交给数据给RTCVideoFrameConsumer，然后再交给didGotVideoFrame:frame 的处理类，通常是美颜类模块。
处理完了，数据交回去的 [videoSource capturer:cameraCapturer didCaptureVideoFrame:frame]; 把属于videoSource的数据还给source，这样就是可以开启后续的处理了。

cameraCapturer = [[RTCCameraVideoCapturer alloc] initWithDelegate:videoFrameConsumer];