UIImageH264Encode

UIImage convert to CVPixelBufferRef ,then be encoded by VideoToolBox api

• UIImageEncode01

  UIImage--> RGBA --> kCVPixelFormatType_420YpCbCr8Planar (YUV420p) --> CVPixelBufferRef --> CMSampleBufferRef --> Encode

• UIImageEncode02 UIImage--> RGBA --> kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange

    `size_t srcPlaneSize = frame_width * frame_height / 4;
    uint8_t *uDataAddr = _outbuffer_yuv + frame_width * frame_height;
    uint8_t *vDataAddr = uDataAddr + frame_width * frame_height / 4 ;
  
    for(size_t i = 0; i< srcPlaneSize; i++){
    	_outbuffer_uv[2*i  ]=uDataAddr[i];
    	_outbuffer_uv[2*i+1]=vDataAddr[i];
    }
    `
  

  --> CVPixelBufferRef --> CMSampleBufferRef --> Encode

  --> 这里说明下，使用 kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange 作为CVPixelBufferRef 的format的话，uv存储要交错存储，对应ffmpeg中avframe理解的话就是二维的，不像Encode01中是三维的类似yuv420p存储。

参考 - https://github.com/manishganvir/iOS-h264Hw-Toolbox - libyuv