Reading Video with the cv::VideoCapture Object
  
  对象创建的三种方法:
  
  // 1. Input filename
  
  cv::VideoCapture::VideoCapture(
  
  const string& filename
  
  );
  
  // 2. Video capture device id
  
  cv::VideoCapture::VideoCapture(
  
  int device
  
  );
  
  // 3.
  
  cv::VideoCapture::VideoCapture();
  
  构造函数的第一种:
  
  在第一种方法中,传入视频路径,创建对象后,需要加入视频是否成功打开:
  
  // e.g.
  
  cv::VideoCapture cap("1.mp4");
  
  if (!cap.isOpen(www.quwanyule157.com)) {
  
  std::cout << "Failed to open the video" << std::endl;
  
  视频打不开的常见原因:
  
  视频路径错误
  
  视频编码格式未知
  
  后一种原因的解决方案:
  
  you will need to have the appropriate library already residing on your computer in order to successfully read the video file.
  
  构造函数的第二种:
  
  通常为设备的代号,整型
  
  小tip:
  
  cv::VideoCapture cap(-1);
  
  1
  
  可打开一个窗口供以选择捕获视频的设备
  
  构造函数的第三种:
  
  cv::VideoCapture cap;
  
  cap.open("video.avi");
  
  1
  
  2
  
  读取视频帧数据
  
  // 1. read function
  
  bool cv::VideoCapture::read(
  
  cv::OutputArray image yongshiyule178.com/// Image into which to read data, return true for read frame successfully, false for failue
  
  );
  
  // 2. >> operator
  
  cv::VideoCapture& cv:www.wanmeiyuele.cn:VideoCapture::operator>>( cv::Mat& image // Image into which to read data
  
  );
  
  // NOTE:
  
  // << return a reference to the original object, should check the return array is not empty
  
  // 3. grab && retrieve function
  
  bool cv::VideoCapture::grab(www.mhylpt.com/ void ); // is designed simply to get it onto the computer as quickly as possible
  
  bool cv::VideoCapture::retrieve(
  
  cv::OutputArray image, // Image into which to read data
  
  int channel = 0 // Used for multihead devices
  
  );
  
  // NOTE:
  
  // can read images from mutiple cameras
  
  // more general
  
  设置&获取视频属性
  
  double cv::VideoCapture::get(
  
  int propid //www.mcyllpt.com Property identifier (see Table 8-4)
  
  );
  
  bool cv::VideoCapture::set(
  
  int propid,
  
  double value // Value to which to set the property
  
  //Example 8-1. Unpacking a four-character code to identify a video codec
  
  cv::VideoCapture cap( "my_video.avi" );
  
  unsigned f = (unsigned)cap.get( cv::CAP_PROP_FOURCC );
  
  char fourcc[] = {
  
  (char) f, // First character is lowest bits
  
  (char)(f >> 8), // Next character is bits 8-15
  
  (char)(f >> 16), // Next character is bits 16-23
  
  (char)(f >> 24), // Last character is bits 24-31
  
  '\0' // and don't forget to terminate
  
  Reading Video with the cv::VideoCapture Object
  
  两种构造方式:
  
  // 1. an uninitialized video object
  
  cv::VideoWriter::VideoWriter();
  
  // 2. an initialized video object
  
  cv::VideoWriter::VideoWriter(
  
  const string& filename, // output filename
  
  int fourcc, // codec, use CV_FOURCC(www.michenggw.com/) macro
  
  double fps, // Frame rate (stored in output file)
  
  cv::Size frame_size, // Size of individual images
  
  bool is_color = true // if false, you can pass gray frames
  
  );
  
  // e.g.
  
  Don’t forget that you are providing characters (single quotes), not strings (double quotes).
  
  同cv::VideoCapture,也有cv::VideoWriter::isOpened()方法暗示是否可以写视频,如果返回false,可能存在以下几点原因:
  
  没有写权限
  
  编码格式不可用
  
  NOTES:
  
  The codecs available to you depend on your operating system installation and the additional libraries you have installed.
  
  For portable code, it is especially important to be able to gracefully handle the case in which the desired codec is not available on any particular machine.
  
  写入视频的两个函数:
  
  // 1. write function
  
  cv::VideoWriter::write(
  
  const Mat& image // Image to write as next frame
  
  );
  
  /*
  
  NOTES:
  
  - This image must have the same size as the size you gave to the writer when you configured it in the first place. - If you told the writer that the frames would be in color, this must also be a three-channel image.
  
  */
  
  // 2. << Operator
  
  my_video_writer << my_frame;
  
  /*
  
  NOTE:
  
  once you have your video writer open, you can write images to the video stream in the same manner you would write to cout or a file ofstream object
  
  简单实例
  
  #include<opencv2/opencv.hpp>
  
  #include<iostream>
  
  using namespace cv;
  
  int main() {
  
  // params & input path && output path configure
  
  int caseVideo = 6;
  
  char pathInVideo[200], pathOutVideo[200];
  
  sprintf(pathInVideo, "%d.avi", caseVideo);
  
  sprintf(pathOutVideo, "%d_output.avi", caseVideo);
  
  // read video
  
  cv::VideoCapture cap(pathInVideo);
  
  if (!cap.isOpened()) {
  
  std::cerr << "Failed to open the video" << std::endl;
  
  return -1;
  
  }
  
  int frameLength = cap.get(CAP_PROP_FRAME_COUNT);
  
  // params for writting output video
  
  cv::VideoWriter outputVideo;
  
  cv::Size sWH = cv::Size((int)cap.get(CAP_PROP_FRAME_WIDTH),
  
  (int)cap.get(CAP_PROP_FRAME_HEIGHT));
  
  if (!outputVideo.open(pathOutVideo, cv::VideoWriter::fourcc('M', 'P', '4', '2'), cap.get(CAP_PROP_FPS), sWH)) {
  
  std::cerr << "Failed to write video" << std::endl;
  
  return -1;
  
  }
  
  // gauss filter frame by frame
  
  for (int i = 0; i < frameLength; i++) {
  
  std::cout << "Process the " << i << " frame" << std::endl;
  
  cv::Mat inputImg, outputImg;
  
  cap.read(inputImg);
  
  if (!inputImg.empty()) {
  
  cv::GaussianBlur(inputImg, outputImg, cv::Size(25, 25), 0.0, 0.0);
  
  outputVideo.write(outputImg);
  
  }
  
  }
  
  // release cap && outputVideo
  
  cap.release();
  
  outputVideo.release();

【学习笔记】Learning OpenCV3——Ch8 working with video的更多相关文章

  1. 流媒体技术学习笔记之(四)解决问题video.js 播放m3u8格式的文件,根据官方的文档添加videojs-contrib-hls也不行的原因解决了

    源码地址:https://github.com/Tinywan/PHP_Experience 总结: 说明: 测试环境:本测试全部来自阿里云直播和OSS存储点播以及本地服务器直播和点播 播放器:Vid ...

  2. 我的Android进阶之旅------>Android中编解码学习笔记

    编解码学习笔记(一):基本概念 媒体业务是网络的主要业务之间.尤其移动互联网业务的兴起,在运营商和应用开发商中,媒体业务份量极重,其中媒体的编解码服务涉及需求分析.应用开发.释放license收费等等 ...

  3. Deep Learning(深度学习)学习笔记整理系列之(八)

    Deep Learning(深度学习)学习笔记整理系列 zouxy09@qq.com http://blog.csdn.net/zouxy09 作者:Zouxy version 1.0 2013-04 ...

  4. 【原】Learning Spark (Python版) 学习笔记(三)----工作原理、调优与Spark SQL

    周末的任务是更新Learning Spark系列第三篇,以为自己写不完了,但为了改正拖延症,还是得完成给自己定的任务啊 = =.这三章主要讲Spark的运行过程(本地+集群),性能调优以及Spark ...

  5. OpenCV学习笔记(一)——OpenCV3.1.0+VS2015开发环境配置

    摘要: 由于最近AR(增强现实)这个概念非常火爆,各种基于AR的应用及游戏逐渐面向大众,而在AR中最重要的两个技术就是跟踪识别和增强渲染,其中跟踪识别是通过OpenCV这个开源的计算机视觉库来实现的, ...

  6. 阅读《LEARNING HARD C#学习笔记》知识点总结与摘要系列文章索引

    从发表第一篇文章到最后一篇文章,时间间隔有整整一个月,虽只有5篇文章,但每一篇文章都是我吸收<LEARNING HARD C#学习笔记>这本书的内容要点及网上各位大牛们的经验,没有半点废话 ...

  7. 阅读《LEARNING HARD C#学习笔记》知识点总结与摘要三

    最近工作较忙,手上有几个项目等着我独立开发设计,所以平时工作日的时候没有太多时间,下班累了就不想动,也就周末有点时间,今天我花了一个下午的时间来继续总结与整理书中要点,在整理的过程中,发现了书中的一些 ...

  8. 阅读《LEARNING HARD C#学习笔记》知识点总结与摘要二

    今天继续分享我的阅读<LEARNING HARD C#学习笔记>知识点总结与摘要二,仍然是基础知识,但可温故而知新. 七.面向对象 三大基本特性: 封装:把客观事物封装成类,并隐藏类的内部 ...

  9. 阅读《LEARNING HARD C#学习笔记》知识点总结与摘要一

    本人有幸在Learning Hard举行的整点抢书活动<Learninghard C#学习笔记>回馈网友,免费送书5本中免费获得了一本<LEARNING HARD C#学习笔记> ...

随机推荐

  1. php GD 圆图 -处理成圆图片

    <?php /** * 处理成圆图片,如果图片不是正方形就取最小边的圆半径,从左边开始剪切成圆形 * @param string $imgpath [description] * @return ...

  2. memcached搭建

    MemCache 安装使用 安装memcached之前首先需要安装libevent, 如果没有安装的请自行去安装. 下载memcache http://www.memcached.org/files/ ...

  3. 基于OMAPL138的Linux字符驱动_GPIO驱动AD9833(二)之cdev与read、write

    基于OMAPL138的Linux字符驱动_GPIO驱动AD9833(二)之cdev与read.write 0. 导语 在上一篇博客里面,基于OMAPL138的字符驱动_GPIO驱动AD9833(一)之 ...

  4. unity独立游戏开发日志2018/09/22

    f::很头痛之前rm做的游戏在新电脑工程打不开了...只能另起炉灶... 还不知道新游戏叫什么名...暂且叫方块世界.(素材已经授权) 首先是规划下场景和素材文件夹的建立. unity常用的文件夹有: ...

  5. 公用的cefsharp窗口

    书接上回,.net实现一个nw,一个字,简单. 结构,无废话,上图. 要说这部分上回展示过的,大致结构如此,其实要说清楚结构,还是得从工作流程开始说起 流程 1.通过桌面的快捷方式启动WebOnDes ...

  6. Gradle 设置本地meaven

    repositories { maven { url uri("F:\\meaven")} }

  7. jmeter插件下载

    https://jmeter-plugins.org/wiki/Start/ 插件下载好后,将插件lib目录下的jar包放在jmeter安装目录下的lib里,插件ext目录下的jar包放在jmeter ...

  8. 线段树简单入门 (含普通线段树, zkw线段树, 主席树)

    线段树简单入门 递归版线段树 线段树的定义 线段树, 顾名思义, 就是每个节点表示一个区间. 线段树通常维护一些区间的值, 例如区间和. 比如, 上图 \([2, 5]\) 区间的和, 为以下区间的和 ...

  9. 「题目代码」P1007~P1012(Java)

    1007 C基础-计负均正 import java.util.*; import java.io.*; public class Main { public static void main(Stri ...

  10. Python 3基础教程32-正则

    本文介绍Python的正则,通过本文介绍和一个练习,对正则有一个基本了解就可以. # 正则表达式 ''' 正则表达式是有一些特殊字符组成,能够帮你找到一些符合一定规则的字符串 先来了解几个符号所代表的 ...