openFrameworks + ofxVideoRecorder setup to record video with h264

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/**
 * openFrameworks + ofxVideoRecorder setup to record video with h264
 * You will need ffmpeg and libx264 in your system. On mac, you can use homebrew.
 * reason for yuv420p:
 * 'QuickTime only supports YUV planar color space with 4:2:0 chroma subsampling (use -vf format=yuv420p or -pix_fmt yuv420p) for H.264 video.'
 * as mentioned here: https://trac.ffmpeg.org/wiki/Encode/H.264
 */

recorder.setVideoCodec("libx264");
string fileName = ofToDataPath("v" + ofGetTimestampString() + ".mp4");
recorder.setupCustomOutput(fbo.getWidth(), fbo.getHeight(), 60, 44100, 0, "-vf format=yuv420p -preset ultrafast " + fileName);