Using C++ to call ffmpeg for rtmp streaming.

title: Using ffmpeg in C++ for rtmp streaming
date: 2021-09-27 16:12:35
comments: true
hide: false
tags:

C++
ffmpeg
opencv
rtmp
categories:
C++
cover: https://image.hauhau.cn/blog/%E6%88%AA%E5%B1%8F2021-09-27%20%E4%B8%8B%E5%8D%884.35.33.png
abbrlink: 4edea31e

Effect 🔅#

Demonstration in Clion

Clion Debugging Effect

No issues when running in the terminal

Effect when running in the terminal

Idea 💡#

Use fork to create a child process to call ffmpeg for streaming. Obtain video frames using OpenCV, transmit them to the child process through a pipeline, and achieve streaming.

Code 🔨#

Note that ffmpeg must be installed on the machine, and the video frame rate must match, otherwise there may be unexpected issues.

main.cc:#

#include <iostream>
#include <csignal>
#include <opencv4/opencv2/opencv.hpp>

bool is_running = true;

void OnSignal(int) {
  is_running = false;
}

int main() {
  // Exit when triggering the following signals
  signal(SIGINT, OnSignal);
  signal(SIGQUIT, OnSignal);
  signal(SIGTERM, OnSignal);

  // Open the camera
  cv::VideoCapture capture(0);
  if (!capture.isOpened()) {
    std::cerr << "Failed to open camera." << std::endl;
    return EXIT_FAILURE;
  }
  capture.set(cv::CAP_PROP_FRAME_WIDTH, 1280);
  capture.set(cv::CAP_PROP_FRAME_HEIGHT, 720);

  std::string rtmp_server_url = "rtmp://localhost:1935/live/test";

  std::stringstream command;
  command << "ffmpeg ";

  // infile options
  command << "-y "  // overwrite output files
          << "-an " // disable audio
          << "-f rawvideo " // force format to rawvideo
          << "-vcodec rawvideo "  // force video rawvideo ('copy' to copy stream)
          << "-pix_fmt bgr24 "  // set pixel format to bgr24
          << "-s 1280x720 "  // set frame size (WxH or abbreviation)
          << "-r 30 "; // set frame rate (Hz value, fraction or abbreviation)

  command << "-i - "; //

  // outfile options
  command << "-c:v libx264 "  // Hyper fast Audio and Video encoder
          << "-pix_fmt yuv420p "  // set pixel format to yuv420p
          << "-preset ultrafast " // set the libx264 encoding preset to ultrafast
          << "-f flv " // force format to flv
          << rtmp_server_url;

  cv::Mat frame;

  // Call ffmpeg for streaming in the child process
  FILE *fp = nullptr;
  fp = popen(command.str().c_str(), "w");

  // Pass each frame read by cv to the child process
  if (fp != nullptr) {
    while (is_running) {
      capture >> frame;
      if (frame.empty()) {
        continue;
      }

      fwrite(frame.data, sizeof(char), frame.total() * frame.elemSize(), fp);
    }
    pclose(fp);
    return EXIT_SUCCESS;
  } else {
    return EXIT_FAILURE;
  }
}

CMakeLists.txt:#

cmake_minimum_required(VERSION 3.20)
project(rtmp_test)

set(CMAKE_CXX_STANDARD 20)

message("")
message("Operation system is ${CMAKE_SYSTEM}")
if (CMAKE_SYSTEM_NAME MATCHES "Linux")
    message("Current platform: Linux")
    link_directories(/usr/local/lib)
    include_directories(/usr/local/include)
    message(STATUS "Load link directories from /usr/local/lib")
    message(STATUS "Load include directories from /usr/local/include")
elseif (CMAKE_SYSTEM_NAME MATCHES "Darwin")
    message("Current platform: Darwin")
    link_directories(/opt/homebrew/lib)
    include_directories(/opt/homebrew/include)
    message(STATUS "Load link directories from /opt/homebrew/lib")
    message(STATUS "Load include directories from /opt/homebrew/include")
    SET(OPENSSL_ROOT_DIR /opt/homebrew/Cellar/openssl@1.1/1.1.1l)
    SET(OPENSSL_INCLUDE_DIR /opt/homebrew/Cellar/openssl@1.1/1.1.1l/include)
else ()
    message(FATAL_ERROR "Platform ${CMAKE_SYSTEM_NAME} is not support for this project")
endif ()

find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})

if (CMAKE_BUILD_TYPE STREQUAL Debug)
    ADD_DEFINITIONS(-DDEBUG)
    message(STATUS "CMake Build Type: Debug")
    message("")
elseif (CMAKE_BUILD_TYPE STREQUAL Release)
    message(STATUS "CMake Build Type: Release")
    message("")
endif ()

file(GLOB ProjectSRC
        "*.cc")

add_executable(${PROJECT_NAME} ${ProjectSRC})
target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})