在做一個數據通道

要求有兩個

1.支持打開實時流，解碼得到圖片

2.支持打開視頻文件，得到解碼圖片

第一個要求前任已經實現

 1 bool FfmpegStreamChr::Open(const char *pstrFilename)
 2 {
 3     Close();
 4     avformat_network_init();
 5     av_register_all();
 6   
 7 
 8     std::string tempfile = pstrFilename;
 9     AVDictionary* options = NULL;
 
10     if (tempfile.size() > 10)
11     {
12         if (memcmp(tempfile.c_str() + tempfile.size() - 4, "#tcp", 4) == 0)
13         {
14             av_dict_set(&options, "rtsp_transport", "tcp", 0);
15             tempfile.erase(tempfile.size() - 4);
16         }
17     }
18 
19     //format_context_ = avformat_alloc_cotext();
 

20 
21     av_dict_set(&options, "stimeout","2000000", 0);
22     if (avformat_open_input(&format_context_, tempfile.c_str(), NULL, &options) < 0)
23     return false;
24 
25     if (avformat_find_stream_info(format_context_, nullptr) < 0)
26     return false;
27 
28     av_dump_format(format_context_, 0
 
, tempfile.c_str(), 0);
29 
30     video_stream_index_ = -1;
31 
32     pts_first = true;
33     duration = format_context_->duration / AV_TIME_BASE;
34 
35     int video_stream_idx = av_find_best_stream(format_context_, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
36     video_st = format_context_->streams[video_stream_idx];
37 
38 
39     for (unsigned int i = 0; i < format_context_->nb_streams; i++)
40     {
41     AVCodecParameters *enc = format_context_->streams[i]->codecpar;
42     if (!enc)
43         continue;
44     if (AVMEDIA_TYPE_VIDEO == enc->codec_type && video_stream_index_ < 0)
45     {
46         width_ = enc->width;
47         height_ = enc->height;
48 
49         codec_ = avcodec_find_decoder(enc->codec_id);
50         if (!codec_)
51         return false;
52         codec_context_ = avcodec_alloc_context3(codec_);
53         if (!codec_context_)
54             return false;
55         if (avcodec_open2(codec_context_, codec_, NULL) < 0)
56         {
57         avcodec_free_context(&codec_context_);
58         return false;
59         }
60 
61         if (width_ && (enc->width != width_))
62         enc->width = width_;
63 
64         if (height_ && (enc->height != height_))
65 
66         enc->height = height_;
67 
68         video_stream_index_ = i;
69     }
70     }
71     if (video_stream_index_ == -1)
72     return false;
73 
74     yuv_frame_ = av_frame_alloc();
75     memset(rgb_data_, 0, sizeof(uint8_t *) * 8);
76     memset(rgb_line_size_, 0, sizeof(int) * 8);
77     rgb_line_size_[0] = 3 * width_;
78     DecodeToImage();
79     return true;
80 }

bool FfmpegStreamChr::DecodeToImage(){
    if (!format_context_ ||!codec_context_)
        return false;
    int count_no_video_stream = 0;
    int continue_counts = 0;
    const int max_number_of_attempts = 250;
   // const int max_number_of_video_stream_attempts = 1 << 16;
    for (;;)
    {
        TempImg = cv::Mat();
        if (continue_counts > max_number_of_attempts)
            return false;

        //    opt_time = GetTickCount();
        int ret = av_read_frame(format_context_, &packet_);

        if (ret == AVERROR(EAGAIN))
        {
            ++continue_counts;
            continue;
        }
        if (ret < 0)
           continue;

        if (packet_.stream_index != video_stream_index_)
        {
           // count_no_video_stream++;
            //if (count_no_video_stream > max_number_of_video_stream_attempts)
            //    return false;
            av_packet_unref(&packet_);
            TempImg.release();
            continue;
        }

       // std::chrono::system_clock::time_point t1 = std::chrono::system_clock::now();
        ret = avcodec_send_packet(codec_context_, &packet_);

        if (avcodec_receive_frame(codec_context_, yuv_frame_) == 0)
        {
            //std::chrono::system_clock::time_point t2 = std::chrono::system_clock::now();
            if (!y2r_sws_context_)
            {
                y2r_sws_context_ = sws_getContext(width_, height_,
                    codec_context_->pix_fmt, codec_context_->width, codec_context_->height, /*video_stream_->codec->pix_fmt*/ AV_PIX_FMT_BGR24, /*SWS_BICUBIC*/ SWS_BILINEAR, NULL, NULL, NULL);
                if (!y2r_sws_context_)
                {
                    av_packet_unref(&packet_);
                    TempImg.release();
                    continue;
                }
            }

            if (!TempImg.data)
                TempImg.create(height_, width_, CV_8UC3);
            rgb_data_[0] = TempImg.data;

            if (sws_scale(y2r_sws_context_, yuv_frame_->data, yuv_frame_->linesize, 0, codec_context_->height, rgb_data_, rgb_line_size_) <= 0)
            {
                av_packet_unref(&packet_);
                TempImg.release();
                av_frame_unref(yuv_frame_);
                return false;
            }

           // std::chrono::system_clock::time_point t3 = std::chrono::system_clock::now();
            //printf("decode : %d , switch : %d\n", std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1).count(), std::chrono::duration_cast<std::chrono::milliseconds>(t3 - t2).count());
            if (pts_first)
            {
                bg_pts = packet_.pts;
                pts_first = false;
            }
            //timestamp = yuv_frame_->pts*av_q2d(video_st->time_base);
           // timestamp = (packet_.pts - bg_pts)*av_q2d(video_st->time_base);
           // durationstamp = duration;

            av_packet_unref(&packet_);
            av_frame_unref(yuv_frame_);
           // return true;
            LOG_DEBUG(100) << "SendToAll \n";
            SendToAll(TempImg);

        }

        ++continue_counts;
        av_packet_unref(&packet_);
    }

}

解碼文件的時候報如下錯

Error splitting the input into NAL units

加入如下代碼添加到open函數的54行後面，正常解碼文件

        //TODO:: add to hanldle file
        if (avcodec_parameters_to_context(codec_context_, enc) < 0){
            return false;
        }

ffempg支持文件解碼