Helper class for exporting video from openFrameworks.

README.md

Video export for openFrameworks

This is a small helper that uses ffmpeg to record h264 video from openFrameworks.

It starts ffmpeg in a subprocess, so ffmpeg should be available on your system. Tested on Linux but probably works on macOS too.

How to use

• Add the videxport.h file to your project and include it.
• VidRecorder::start to start ffmpeg and configure output filename and framerate.
• VidRecorder::recordViewport adds a frame to the video file.
• VidRecorder::finish stops ffmpeg.
• Watch the console output for errors and messages from the ffmpeg process.
• All functions return false if something goes wrong (see the example file draw function).

example.cpp

#include "ofApp.h"
#include "ofMain.h"

#include "videxport.h"

class VidRecorderExample : public ofBaseApp {
public:
  void setup() {
    ofBackground(ofColor::gray);
    ofSetBackgroundAuto(false);
    recorder.start("example.mp4", 60);
    position.x = 0;
    position.y = ofGetViewportHeight() / 2;
  }
  void update() {
    position.x =
        ofGetViewportWidth() * static_cast<float>(ofGetFrameNum()) / 300;
  }
  void draw() {
    ofSetColor(ofColor::white, 16);
    ofFill();
    ofDrawRectangle(0, 0, ofGetViewportWidth(), ofGetViewportHeight());
    ofSetColor(ofColor::black);
    ofDrawCircle(position, 100);
    bool recording = recorder.recordViewport();
    if (!recording) {
      ofExit();
    }
    if (ofGetFrameNum() > 300) {
      recorder.finish();
      ofExit();
    }
  }

  ofPoint position;
  VidRecorder recorder;
};

int main() {
  ofSetupOpenGL(1000, 1000, OF_WINDOW);
  ofSetFrameRate(60);
  ofSetVerticalSync(true);
  ofRunApp(new VidRecorderExample());
}

videxport.h

#ifndef VIDEXPORT_H
#define VIDEXPORT_H

#include <stdio.h>

#include "ofMain.h"

extern template class ofPixels_<unsigned char>;

struct VidRecorder {
  FILE *f = nullptr;
  ofPixels p;
  ofBuffer b;
  void logError(std::string m) { ofLogError("VidRecorder", m); }
  bool start(std::string filename, unsigned int fps = 60) {
    // If we don't call this and ffmpeg crashes, the whole app stops.
    signal(SIGPIPE, SIG_IGN);
    std::stringstream cmd;
    cmd << "ffmpeg "
        << "-f image2pipe "
        << "-framerate " << fps << " -i - -c:v libx264 -pix_fmt yuv420p "
        << filename;
    f = popen(cmd.str().c_str(), "w");
    if (!f) {
      logError(std::string(strerror(errno)));
      return false;
    }
    return true;
  }
  bool recordViewport() {
    if (!f) {
      logError("File handle is null.");
      return false;
    }
    ofGetGLRenderer()->saveFullViewport(p);
    ofSaveImage(p, b, OF_IMAGE_FORMAT_BMP);
    auto written = fwrite(b.getData(), sizeof(char), b.size(), f);
    if (written != b.size()) {
      logError(std::string(strerror(errno)));
      return false;
    }
    return true;
  }
  bool finish() {
    if (!f) {
      logError("File handle is null.");
      return false;
    }
    auto r = pclose(f);
    if (r == -1) {
      logError(std::string(strerror(errno)));
      f = nullptr;
      return false;
    }
    f = nullptr;
    return true;
  }
};

#endif // VIDEXPORT_H