yjxiong/OpenCV H264 VideoWriter.md

## OpenCV H264 VideoWriter.md

      
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              OpenCV H264 VideoWriter.md
            
          
    To use OpenCV's VideoWriter class to write an H264 encoded video, one would encounter some error like
Could not open codec libx264: unspecified error

Here is the trick. Beforehand, one has to make sure

--enable-libx264 is switched on in ffmpeg
OpenCV is downloaded in sources.

Then make following changes to modules/highgui/src/cap_ffmpeg_impl.hpp:
    ...
    c->bit_rate = (int)lbit_rate;

    /************** modifications to enable x264 writer ************************/
    c->me_range = 16;
    c->max_qdiff = 4;
    c->qmin = 1;
    c->qmax = 30;
    c->qcompress = 0.9;
    c->qcompress = 0.6;
    /************** end of modificaiton ****************************************/
  

    /* open the codec */
    if ((err=
#if LIBAVCODEC_VERSION_INT >= ((53<<16)+(8<<8)+0)
         avcodec_open2(c, codec, NULL)
#else
         avcodec_open(c, codec)
#endif
         ) < 0) {
        fprintf(stderr, "Could not open codec '%s': %s", codec->name, icvFFMPEGErrStr(err));
        return false;
    }


Compile OpenCV, then you will be able to use the VideoWriter with FOURCC H264.