完整的核心函数示例如下：

public int AddStream(AVStream* in_stream, bool isAudioDemuxer = false)
{
	int ret = -1;
	if (in_stream == null || (in_stream->codecpar->codec_type != AVMEDIA_TYPE_VIDEO && in_stream->codecpar->codec_type != AVMEDIA_TYPE_AUDIO)) return ret;
	AVStream *out_stream;
	var in_codecpar = in_stream->codecpar;
	out_stream = avformat_new_stream(fmtCtx, null);
	if (out_stream == null) return -1;
	ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
	if (ret < 0) return ret;
	AVDictionaryEntry* b = null;
	while (true)
	{
		b = av_dict_get(in_stream->metadata, "", b, AV_DICT_IGNORE_SUFFIX);
		if (b == null) break;
		if (Utils.BytePtrToStringUTF8(b->key).ToLower() == "language" || Utils.BytePtrToStringUTF8(b->key).ToLower() == "lang")
			av_dict_set(&out_stream->metadata, Utils.BytePtrToStringUTF8(b->key), Utils.BytePtrToStringUTF8(b->value), 0);
	}
	out_stream->codecpar->codec_tag = 0;	
	if (isAudioDemuxer)
	{
		mapInOutStreams2.Add((IntPtr)in_stream, (IntPtr)out_stream);
		mapInInStream2.Add(in_stream->index, (IntPtr)in_stream);
	}
	else
	{
		mapInOutStreams.Add((IntPtr)in_stream, (IntPtr)out_stream);
		mapInInStream.Add(in_stream->index, (IntPtr)in_stream);
	}
	return 0;
}

avformat_new_stream：Add a new stream to a media file.

avcodec_parameters_copy：ccopy the contents of src to dst any allocated fields in dst are freed and replaced with newly allocated duplicates of the corresponding fields in src.

av_dict_get：Get a dictionary entry with matching key.

av_dict_set：Set the given entry in *pm, overwriting an existing entry.