项目场景：

使用ffmpeg拉取rtsp服务器的码流，并且推rtmp流到nginx，web前端使用flv码流进行点播；
拉流以及推流使用的是ffmpeg原生接口；
点播服务器使用是NGINX，并集成了http-flv模块（可以参考我的其他文档。）

问题描述：

        AVStream *in_stream = ifmt_ctx->streams[videoindex];        AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);       ......        //复制AVCodecContext的设置（Copy the settings of AVCodecContext）        ret = avcodec_copy_context(out_stream->codec, in_stream->codec);       ......       //紧接着调用打开、写入头、设置一些参数、循环读取数据、写入数据        ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);       ......          ret = avformat_write_header(ofmt_ctx, /*NULL*/&options);     	......         av_dump_format(ofmt_ctx, 0, out_filename, 1);       ......        while (m_bRun)        {            AVStream *in_stream, *out_stream;            ret = av_read_frame(ifmt_ctx, &pkt);            if (ret < 0)            {                int err_code = ret;                char buf[1024] = { 0 };                if (ret < 0) {                    av_strerror(err_code, buf, 1024);                    qDebug()<<buf;						//在此处报错                               }                         }			......                    ret = av_interleaved_write_frame(ofmt_ctx, &pkt);        }

原因分析：

1. 抓包分析

   通过抓包看，是nginx服务器主动结束了连接；

2. 分析nginx日志
   由于是在 av_interleaved_write_frame函数发生了异常，该函数直接作用是将“h264数据”送至nginx服务器，所以进一步打开nginx debug日志等级，错误日志如下：

2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 02 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0A ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (10) 6F 6E 4D 65 74 61 44 61 74 61 ‘onMetaData’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 03 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 06 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (6) 53 65 72 76 65 72 ‘Server’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 02 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 44 ‘?D’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (68) 4E 47 49 4E 58 20 48 54 54 50 2D 46 4C 56 20 28 ‘NGINX HTTP-FLV (’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 05 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (5) 77 69 64 74 68 ‘width’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 40 84 00 00 00 00 00 00 ‘@???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 06 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (6) 68 65 69 67 68 74 ‘height’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 40 7E 00 00 00 00 00 00 ‘@~???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0C ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (12) 64 69 73 70 6C 61 79 57 69 64 74 68 ‘displayWidth’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 40 84 00 00 00 00 00 00 ‘@???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0D ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (13) 64 69 73 70 6C 61 79 48 65 69 67 68 74 ‘displayHeight’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 40 7E 00 00 00 00 00 00 ‘@~???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 08 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 64 75 72 61 74 69 6F 6E ‘duration’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 09 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (9) 66 72 61 6D 65 72 61 74 65 ‘framerate’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 03 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (3) 66 70 73 ‘fps’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0D ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (13) 76 69 64 65 6F 64 61 74 61 72 61 74 65 ‘videodatarate’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0C ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (12) 76 69 64 65 6F 63 6F 64 65 63 69 64 ‘videocodecid’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 40 1C 00 00 00 00 00 00 ‘@???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0D ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (13) 61 75 64 69 6F 64 61 74 61 72 61 74 65 ‘audiodatarate’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 0C ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (12) 61 75 64 69 6F 63 6F 64 65 63 69 64 ‘audiocodecid’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 00 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (8) 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 07 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (7) 70 72 6F 66 69 6C 65 ‘profile’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 02 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 20 "? ’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (32) 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 05 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (5) 6C 65 76 65 6C ‘level’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 02 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 20 "? ’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (32) 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ‘???’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (2) 00 00 ‘??’
2021/09/22 20:07:50 [debug] 1729538#0: *17 AMF write (1) 09 ‘?’
2021/09/22 20:07:50 [debug] 1729538#0: *17 RTMP prep amf_meta (18) fmt=0 csid=5 timestamp=0 mlen=409 msid=1 nbufs=4
2021/09/22 20:07:50 [debug] 1729538#0: *17 reusing formerly read data: 17
2021/09/22 20:07:50 [debug] 1729538#0: *17 RTMP bheader fmt=0 csid=6
2021/09/22 20:07:50 [debug] 1729538#0: *17 RTMP mheader fmt=0 video (9) time=0+0 mlen=5 len=0 msid=1
2021/09/22 20:07:50 [debug] 1729538#0: *17 RTMP recv video (9) csid=6 timestamp=0 mlen=5 msid=1 nbufs=1
2021/09/22 20:07:50 [debug] 1729538#0: *17 nhandlers: 6
2021/09/22 20:07:50 [debug] 1729538#0: *17 calling handler 0
2021/09/22 20:07:50 [debug] 1729538#0: *17 codec: avc header 1700000000
2021/09/22 20:07:50 [error] 1729538#0: *17 123456 codec: invalid video codec header size=5, client: 172.21.34.145, server: 0.0.0.0:1935
2021/09/22 20:07:50 [debug] 1729538#0: *17 handler 0 failed
2021/09/22 20:07:50 [debug] 1729538#0: *17 finalize session
2021/09/22 20:07:50 [debug] 1729538#0: *17 post event 0000000001654C48
2021/09/22 20:07:50 [debug] 1729538#0: timer delta: 42
2021/09/22 20:07:50 [debug] 1729538#0: posted event 0000000001654C48
2021/09/22 20:07:50 [debug] 1729538#0: *17 delete posted event 0000000001654C48
2021/09/22 20:07:50 [debug] 1729538#0: *17 close session
2021/09/22 20:07:50 [info] 1729538#0: *17 disconnect, client: 172.21.34.145, server: 0.0.0.0:1935

2021/09/22 20:07:50 [debug] 1729538#0: *17 codec: avc header 1700000000
2021/09/22 20:07:50 [error] 1729538#0: *17 123456 codec: invalid video codec header size=5, client: 172.21.34.145, server: 0.0.0.0:1935

avc header 是h264的编码头，这一段是无效数据，导致了异常，以及后面的close session;

3. ffmpeg 函数对应的avc header是哪？
   对应下面数据结构中的“ extradata”；

typedef struct AVCodecParameters {    /**     * General type of the encoded data.     */    enum AVMediaType codec_type;    /**     * Specific type of the encoded data (the codec used).     */    enum AVCodecID   codec_id;    /**     * Additional information about the codec (corresponds to the AVI FOURCC).     */    uint32_t         codec_tag;    /**     * Extra binary data needed for initializing the decoder, codec-dependent.     *     * Must be allocated with av_malloc() and will be freed by     * avcodec_parameters_free(). The allocated size of extradata must be at     * least extradata_size + AV_INPUT_BUFFER_PADDING_SIZE, with the padding     * bytes zeroed.     */    uint8_t *extradata;    /**     * Size of the extradata content in bytes.     */    int      extradata_size;    /**     * - video: the pixel format, the value corresponds to enum AVPixelFormat.     * - audio: the sample format, the value corresponds to enum AVSampleFormat.     */    int format;    /**     * The average bitrate of the encoded data (in bits per second).     */    int64_t bit_rate;    /**     * The number of bits per sample in the codedwords.     *     * This is basically the bitrate per sample. It is mandatory for a bunch of     * formats to actually decode them. It"s the number of bits for one sample in     * the actual coded bitstream.     *     * This could be for example 4 for ADPCM     * For PCM formats this matches bits_per_raw_sample     * Can be 0     */    int bits_per_coded_sample;    /**     * This is the number of valid bits in each output sample. If the     * sample format has more bits, the least significant bits are additional     * padding bits, which are always 0. Use right shifts to reduce the sample     * to its actual size. For example, audio formats with 24 bit samples will     * have bits_per_raw_sample set to 24, and format set to AV_SAMPLE_FMT_S32.     * To get the original sample use "(int32_t)sample >> 8"."     *     * For ADPCM this might be 12 or 16 or similar     * Can be 0     */    int bits_per_raw_sample;    /**     * Codec-specific bitstream restrictions that the stream conforms to.     */    int profile;    int level;    /**     * Video only. The dimensions of the video frame in pixels.     */    int width;    int height;    /**     * Video only. The aspect ratio (width / height) which a single pixel     * should have when displayed.     *     * When the aspect ratio is unknown / undefined, the numerator should be     * set to 0 (the denominator may have any value).     */    AVRational sample_aspect_ratio;    /**     * Video only. The order of the fields in interlaced video.     */    enum AVFieldOrder                  field_order;    /**     * Video only. Additional colorspace characteristics.     */    enum AVColorRange                  color_range;    enum AVColorPrimaries              color_primaries;    enum AVColorTransferCharacteristic color_trc;    enum AVColorSpace                  color_space;    enum AVChromaLocation              chroma_location;    /**     * Video only. Number of delayed frames.     */    int video_delay;    /**     * Audio only. The channel layout bitmask. May be 0 if the channel layout is     * unknown or unspecified, otherwise the number of bits set must be equal to     * the channels field.     */    uint64_t channel_layout;    /**     * Audio only. The number of audio channels.     */    int      channels;    /**     * Audio only. The number of audio samples per second.     */    int      sample_rate;    /**     * Audio only. The number of bytes per coded audio frame, required by some     * formats.     *     * Corresponds to nBlockAlign in WAVEFORMATEX.     */    int      block_align;    /**     * Audio only. Audio frame size, if known. Required by some formats to be static.     */    int      frame_size;    /**     * Audio only. The amount of padding (in samples) inserted by the encoder at     * the beginning of the audio. I.e. this number of leading decoded samples     * must be discarded by the caller to get the original audio without leading     * padding.     */    int initial_padding;    /**     * Audio only. The amount of padding (in samples) appended by the encoder to     * the end of the audio. I.e. this number of decoded samples must be     * discarded by the caller from the end of the stream to get the original     * audio without any trailing padding.     */    int trailing_padding;    /**     * Audio only. Number of samples to skip after a discontinuity.     */    int seek_preroll;} AVCodecParameters;

4. 常规手段之，打印分析in_stream 以及out_stream的对应的parameter参数中的exteradata字段；
   加入以下代码，将

void myprintf(uint8_t* data,int len){    QString disp_string,S;    QByteArray ba;    ba.resize(len);    QString m_strMSG = QString("myprintf len=:%1").arg(len);    for (int i = 0 ;i < len; i++)    {        ba[i] = data[i];    }    for(int i=0;i<ba.size();i++)    {        S.sprintf("0x%02x, ", (unsigned char)ba.at(i));        disp_string += S;    }       qDebug()<<m_strMSG<<"/n";       qDebug()<<disp_string<<"/n";}......//进行打印 myprintf(out_stream->codecpar->extradata,out_stream->codecpar->extradata_size);

解决方案：

文章的最后：如果需要研究flv封装格式的特点，可以具体搜索网络资源。