Why do you use new Codec() object in examples? about avcpp HOT 2 OPEN

vdec = VideoDecoderContext(vst);

CodecContext2(vst, Codec(), Direction::Decoding, AVMEDIA_TYPE_VIDEO)

... CodecContext2()...
...
    Codec c = codec;
    if (codec.isNull())
    {
        if (st.direction() == Direction::Decoding)
            c = findDecodingCodec(codecId);
        else
            c = findEncodingCodec(codecId);
    }
...

vdec.open(ec);

vdec.open(Codec(), ec);

void CodecContext2::open(const Codec &codec, AVDictionary **options, OptionalErrorCode ec)
{
    clear_if(ec);

    if (isOpened() || !isValid()) {
        throws_if(ec, isOpened() ? Errors::CodecAlreadyOpened : Errors::CodecInvalid);
        return;
    }

    int stat = avcodec_open2(m_raw, codec.raw(), options);
    if (stat < 0)
        throws_if(ec, stat, ffmpeg_category());
}

 * @param codec The codec to open this context for. If a non-NULL codec has been
 *              previously passed to avcodec_alloc_context3() or
 *              for this context, then this parameter MUST be either NULL or
 *              equal to the previously passed codec.