ffmpeg - 在 avio_open() 函数执行之前，它与 RTMP 服务器没有连接

Question

我是 ffmpeg API 的初学者。我认为连接到 RTMP 服务器的函数是 avio_open() 函数。在我的代码中，在执行 avio_open() 函数之前，它与 RTMP 服务器没有连接。我是否理解正确。
我这个时候有个问题:客户端连接RTMP服务器后5秒内RTMP服务器没有找到关键帧，服务器将关闭连接。
但是根据我的理解，客户端在连接服务器之前已经找到了关键帧，所以服务器应该也找到了关键帧。为什么找不到关键帧？

#include "/usr/local/include/libavcodec/avcodec.h"
#include "/usr/local/include/libavformat/avformat.h"
#include "/usr/local/include/libavfilter/avfilter.h"
#include "/usr/local/include/libavutil/mathematics.h"
#include "/usr/local/include/libavutil/time.h"

extern VideoDataStruct *VideoDataListHeader;
extern PushVideoStruct PushVideoInfo;
extern enum IsPushingVideo IsPushingVideoFlag;
extern UCHAR ChangeAnotherVideo;
typedef long long int64;


#define READ_BUF_LEN       1024*12

extern enum IsStopPushVideo StopPushVideoFlag;  

static int read_packet(void *opaque, uint8_t *buf, int buf_size)
{
    int64 dataLen = 0;

    while (dataLen < buf_size)
    {
        if ((VideoDataListHeader != NULL) && (VideoDataListHeader->flag == 1))
        {
            memcpy(&buf[dataLen], VideoDataListHeader->buf, sizeof(VideoDataListHeader->buf));
            dataLen += sizeof(VideoDataListHeader->buf);

            VideoDataListHeader->flag = 0;
            VideoDataListHeader = VideoDataListHeader->next;
        }
        else 
        {
            usleep(10000);
        }
    }
    return buf_size;
}

void *PushVideoFunction(void *arg)
{
    AVFormatContext *m_pFmtCtx = NULL;
    AVPacket pkt;   
    AVIOContext *m_pIOCtx = NULL;
    AVInputFormat *in_fmt = NULL;
    int ret = 0;
    unsigned int i = 0;
    int vid_idx =-1;
    unsigned char *m_pIOBuf = NULL;
    int m_pIOBuf_size = READ_BUF_LEN;
    int64 start_time = 0;
    int frame_index = 0;
    //const char *rtmp_url = "rtmp://192.168.1.108/mytv/01";
    char rtmp_url[140] = {0};
    memset(rtmp_url, 0, sizeof(rtmp_url));
    strcpy(rtmp_url, PushVideoInfo.VideoServer);
    CHAR fileName[64] = {0};

    avformat_network_init(); 
    if (strcmp(PushVideoInfo.VideoType, REAL_VIDEO) == 0) 
    {
        m_pIOBuf = (unsigned char*)av_malloc(m_pIOBuf_size);
        if(m_pIOBuf == NULL)
        {
            printf("av malloc failed!\n");
            goto end;
        }

    
        m_pIOCtx = avio_alloc_context(m_pIOBuf, m_pIOBuf_size, 0, NULL, read_packet, NULL, NULL);       
        if (!m_pIOCtx) 
        {
            printf("avio alloc context failed!\n");
            goto end;
        }

    
        m_pFmtCtx = avformat_alloc_context();
        if (!m_pFmtCtx)  
        {
            printf("avformat alloc context failed!\n");
            goto end;
        }


        //m_pFmtCtx->probesize = BYTES_PER_FRAME * 8;
        m_pFmtCtx->pb = m_pIOCtx;  
        ret = avformat_open_input(&m_pFmtCtx, "", in_fmt, NULL);
    }
    else if (strcmp(PushVideoInfo.VideoType, HISTORY_VIDEO) == 0) 
    {
        sprintf(fileName, "%s", VIDEO_FILE_FOLDER);
        sprintf(fileName+strlen(fileName), "%s", PushVideoInfo.VideoFile);
        ret = avformat_open_input(&m_pFmtCtx, fileName, NULL, NULL);
    }
    if (ret < 0)
    {
        printf("avformat open failed!\n");
        goto end;           
    }

    ret = avformat_find_stream_info(m_pFmtCtx, 0);
    if (ret < 0)
    {
        printf("could not find stream info!\n");
        goto end;           
    }       
    for(i = 0; i < m_pFmtCtx->nb_streams; i++)
    {
        if((m_pFmtCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) && (vid_idx < 0))
        {
            vid_idx = i;
        }
    }

    AVFormatContext *octx = NULL;

    ret = avformat_alloc_output_context2(&octx, 0, "flv", rtmp_url);
    if (ret < 0)
    {
        printf("avformat alloc output context2 failed!\n");
        goto end;
    }   

    av_init_packet(&pkt);    

    
    for (i = 0;i < m_pFmtCtx->nb_streams; i++)
    {
        AVCodec *codec = avcodec_find_decoder(m_pFmtCtx->streams[i]->codecpar->codec_id);
        AVStream *out = avformat_new_stream(octx, codec);
        ret = avcodec_parameters_copy(out->codecpar, m_pFmtCtx->streams[i]->codecpar);
        out->codecpar->codec_tag = 0;
    }

    ret = avio_open(&octx->pb, rtmp_url, AVIO_FLAG_WRITE);
    if (!octx->pb)
    {
        printf("avio open failed!\n");
        goto end;       
    }

    ret = avformat_write_header(octx, 0);
    if (ret < 0)
    {
        printf("avformat write header failed!\n");
        goto end;           
    }

    start_time = av_gettime();
    AVStream *in_stream, *out_stream;
    AVRational time_base1;
    AVRational time_base;
    AVRational time_base_q;
    int64 calc_duration;
    int64 pts_time;
    int64 now_time;
    
    ChangeAnotherVideo = 0;
    while((!StopPushVideoFlag) && (ChangeAnotherVideo == 0))
    {
        ret = av_read_frame(m_pFmtCtx, &pkt);
        if (ret < 0)
        {
            break;
        }
        if (pkt.pts == AV_NOPTS_VALUE)
        {
            time_base1 = m_pFmtCtx->streams[vid_idx]->time_base;
            calc_duration = (double)AV_TIME_BASE/av_q2d(m_pFmtCtx->streams[vid_idx]->r_frame_rate);
            
            pkt.pts = (double)(frame_index*calc_duration)/(double)(av_q2d(time_base1)*AV_TIME_BASE);
            pkt.dts = pkt.pts;
            pkt.duration = (double)calc_duration/(double)(av_q2d(time_base1)*AV_TIME_BASE);
        }
        if (pkt.stream_index == vid_idx)
        {
            time_base = m_pFmtCtx->streams[vid_idx]->time_base;
            time_base_q = (AVRational){1, AV_TIME_BASE};            
            pts_time = av_rescale_q(pkt.dts, time_base, time_base_q);
            now_time = av_gettime() - start_time;
            if (pts_time > now_time)
            {
                av_usleep(pts_time - now_time);
            }
        }
        in_stream  = m_pFmtCtx->streams[pkt.stream_index];
        out_stream = octx->streams[pkt.stream_index];
        pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, (enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
        pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
        pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
        pkt.pos = -1;
        if(pkt.stream_index == vid_idx)
        {
            printf("Send %8d video frames to output URL\n",frame_index);
            frame_index++;
        }
        ret = av_interleaved_write_frame(octx, &pkt);
        if (ret < 0)
        {
            goto end;
        }
        av_packet_unref(&pkt);
    }
    
end:
    printf("---------------------------------stop push video -------------------------------------------\n");
    StopPushVideoFlag = NO_STOP_PUSH;
    IsPushingVideoFlag = NO_PUSHING;    
    ChangeAnotherVideo = 0;
    avformat_close_input(&m_pFmtCtx);
    if (octx)
    {
        avio_closep(&octx->pb);
        avformat_free_context(octx);
    }
    /* note: the internal buffer could have changed, and be != avio_ctx_buffer */
    if (m_pIOCtx) 
    {
        av_freep(&m_pIOCtx->buffer);
        av_freep(&m_pIOCtx);
    }

    if (ret < 0) 
    {
        printf("Error occured : %s\n", av_err2str(ret));
        //return 1;
    }
    pthread_exit((void*)"push video end!"); 
    
}


void PushVideo(void)
{
    int ret = 0;
    pthread_t pushVideoThread;

    ret = pthread_create(&pushVideoThread, NULL, PushVideoFunction, NULL);
    if(ret != 0)
    {
        printf("error : push video thread create failed!\n");
        exit(-1);
    }
    else
    {
        printf("(debug) push video thread create success!\n");
    } 
} 

Answer 1

关于未找到关键帧:
因为我在缓存视频数据的时候，没有用SPS、PPS、I帧缓存，所以执行AA函数的时候会报这些错误。
虽然这些错误不会影响后续的推流过程，但是为了减少这些错误的显示，我在缓存数据之前找到了SPS&PPS&I帧。
关于断开连接:
客户端有一个 0x0a 类型的 Nalu，服务器不知道。因此，服务器发送一个 FIN 消息并断开连接。不是因为找不到关键帧。