/// <summary>
        /// 开启线程
        /// </summary>
        /// <param name="fileName"></param>
        /// <param name="sdlVideo"></param>
        public void Start(string fileName, SDLHelper sdlvideo, SDLAudio sdlAudio)
        {
            // 视频线程
            threadVideo = new Thread(() =>
            {
                try
                {
                    RunVideo(fileName, sdlvideo);
                }
                catch (Exception ex)
                {
                    Console.WriteLine("JT1078CodecForMp4.Run Video", ex);
                }
            });
            threadVideo.IsBackground = true;
            threadVideo.Start();

            // 音频线程
            //threadAudio = new Thread(() =>
            //{
            //    try
            //    {
            //        RunAudio(fileName, sdlAudio);
            //    }
            //    catch (Exception ex)
            //    {
            //        Console.WriteLine("JT1078CodecForMp4.Run Audio", ex);
            //    }
            //});
            //threadAudio.IsBackground = true;
            //threadAudio.Start();
        }
        /// <summary>
        /// 音频AAC转PCM并使用SDL进行播放
        /// </summary>
        /// <param name="fileName"></param>
        /// <param name="sdlAudio"></param>
        /// <returns></returns>
        public unsafe int RunAudio(string fileName, SDLAudio sdlAudio)
        {
            IsRun        = true;
            exit_thread  = false;
            pause_thread = false;
            threadAudio  = Thread.CurrentThread;
            int error, frame_count = 0;
            int got_frame, ret;
            AVFormatContext *ofmt_ctx = null;
            SwsContext *     pSwsCtx  = null;
            IntPtr           convertedFrameBufferPtr = IntPtr.Zero;

            try
            {
                // 注册编解码器
                ffmpeg.avcodec_register_all();

                // 获取文件信息上下文初始化
                ofmt_ctx = ffmpeg.avformat_alloc_context();

                // 打开媒体文件
                error = ffmpeg.avformat_open_input(&ofmt_ctx, fileName, null, null);
                if (error != 0)
                {
                    throw new ApplicationException($"ffmepg avformat_open_input error: {error}");
                }

                // 获取流的通道
                for (int i = 0; i < ofmt_ctx->nb_streams; i++)
                {
                    if (ofmt_ctx->streams[i]->codec->codec_type == AVMediaType.AVMEDIA_TYPE_AUDIO)
                    {
                        audioindex = i;
                        Console.WriteLine("audio.............." + audioindex);
                    }
                }

                if (audioindex == -1)
                {
                    Console.WriteLine("Couldn't find a  audio stream.(没有找到音频流)");
                    return(-1);
                }

                // 音频流处理
                if (audioindex > -1)
                {
                    //根据索引拿到对应的流,根据流拿到解码器上下文
                    AVCodecContext *pCodeCtx = ofmt_ctx->streams[audioindex]->codec;

                    //再根据上下文拿到编解码id,通过该id拿到解码器
                    AVCodec *pCodec = ffmpeg.avcodec_find_decoder(pCodeCtx->codec_id);
                    if (pCodec == null)
                    {
                        Console.WriteLine("没有找到编码器");
                        return(-1);
                    }
                    //打开编码器
                    if (ffmpeg.avcodec_open2(pCodeCtx, pCodec, null) < 0)
                    {
                        Console.WriteLine("编码器无法打开");
                        return(-1);
                    }
                    Console.WriteLine("Find a  audio stream. channel=" + audioindex);

                    //编码数据
                    AVPacket *packet = (AVPacket *)ffmpeg.av_malloc((ulong)(sizeof(AVPacket)));
                    //解压缩数据
                    AVFrame *frame = ffmpeg.av_frame_alloc();

                    //frame->16bit 44100 PCM 统一音频采样格式与采样率
                    SwrContext *swrCtx = ffmpeg.swr_alloc();
                    //重采样设置选项-----------------------------------------------------------start
                    //输入的采样格式
                    AVSampleFormat in_sample_fmt = pCodeCtx->sample_fmt;
                    //输出的采样格式 16bit PCM
                    AVSampleFormat out_sample_fmt = AVSampleFormat.AV_SAMPLE_FMT_S16;
                    //输入的采样率
                    int in_sample_rate = pCodeCtx->sample_rate;
                    //输出的采样率
                    int out_sample_rate = 44100;
                    //输入的声道布局
                    long in_ch_layout = (long)pCodeCtx->channel_layout;
                    //输出的声道布局
                    int out_ch_layout = ffmpeg.AV_CH_LAYOUT_MONO;

                    ffmpeg.swr_alloc_set_opts(swrCtx, out_ch_layout, out_sample_fmt, out_sample_rate, in_ch_layout, in_sample_fmt, in_sample_rate, 0, null);
                    ffmpeg.swr_init(swrCtx);
                    //重采样设置选项-----------------------------------------------------------end
                    //获取输出的声道个数
                    int out_channel_nb = ffmpeg.av_get_channel_layout_nb_channels((ulong)out_ch_layout);
                    //存储pcm数据
                    byte *out_buffer = (byte *)ffmpeg.av_malloc(2 * 44100);

                    //一帧一帧读取压缩的音频数据AVPacket
                    while (ffmpeg.av_read_frame(ofmt_ctx, packet) >= 0)
                    {
                        // 退出线程
                        if (exit_thread)
                        {
                            break;
                        }
                        // 暂停解析
                        if (pause_thread)
                        {
                            while (pause_thread)
                            {
                                Thread.Sleep(100);
                            }
                        }
                        if (packet->stream_index == audioindex)
                        {
                            //解码AVPacket->AVFrame
                            ret = ffmpeg.avcodec_decode_audio4(pCodeCtx, frame, &got_frame, packet);
                            if (ret < 0)
                            {
                                Console.WriteLine("音频解码失败");
                                return(-1);
                            }
                            // 读取帧数据
                            if (got_frame > 0)
                            {
                                frame_count++;
                                Console.WriteLine("音频帧数:第 " + frame_count + " 帧");
                                var data_ = frame->data;
                                ffmpeg.swr_convert(swrCtx, &out_buffer, 2 * 44100, (byte **)&data_, frame->nb_samples);
                                //获取sample的size
                                int out_buffer_size = ffmpeg.av_samples_get_buffer_size(null, out_channel_nb, frame->nb_samples, out_sample_fmt, 1);
                                //写入文件进行测试
                                var data = out_buffer;
                                sdlAudio.PlayAudio((IntPtr)data, out_buffer_size);
                            }
                        }
                        ffmpeg.av_free_packet(packet);
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
            finally
            {
                if (&ofmt_ctx != null)
                {
                    ffmpeg.avformat_close_input(&ofmt_ctx);//关闭流文件
                }
            }
            IsRun = false;
            return(0);
        }