基于FFMPEG封装aac及h264为FargmentMP4

FargmentMP4是一种特殊的MP4，这边他的特点及格式，不再详细说明 ，网上资料不少可以进行参考。

这边说下基于FFMPEG封装aac及h264为FargmentMP4的步骤：

1.  
   关键代码：
2.  
   1、创建两个输入对象和一个输出对象并打开。
3.  
   AVFormatContext *ifmt_ctx_v = NULL, *ifmt_ctx_a = NULL, *ofmt_ctx = NULL;
4.  
   if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, NULL, NULL)) < 0) {
5.  
   printf("Could not open input file.");
6.  
   goto end;
7.  
   }
8.  
   // printf("=====2========RET:%d\n",ret);
9.  
   if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {
10.  
    printf("Failed to retrieve input stream information");
11.  
    if (acc_length > 0)
12.  
    goto end;
13.  
    }
14.  
     
15.  
    if ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, NULL, NULL)) < 0) {
16.  
    printf("Could not open input file:%d\n", ret);
17.  
    goto end;
18.  
    }
19.  
    if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {
20.  
    printf("Failed to retrieve input stream information");
21.  
    goto end;
22.  
    }
23.  
    avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
24.  
    if (!ofmt_ctx) {
25.  
    printf("Could not create output context\n");
26.  
    ret = AVERROR_UNKNOWN;
27.  
    goto end;
28.  
    }
29.  
    ofmt = ofmt_ctx->oformat;
30.  
     
31.  
    2、初始化过滤器 因为aac打包到mp4需要去掉adts头。
32.  
    const AVBitStreamFilter *absFilter = av_bsf_get_by_name("aac_adtstoasc");
33.  
    AVBSFContext *absCtx = NULL;
34.  
    av_bsf_alloc(absFilter, &absCtx);
35.  
     
36.  
    3、获取视频流信息并拷贝相应编码格式
37.  
    for (i = 0; i < ifmt_ctx_v->nb_streams; i++) {
38.  
    //Create output AVStream according to input AVStream
39.  
    if (ifmt_ctx_v->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
40.  
    AVStream *in_stream = ifmt_ctx_v->streams[i];
41.  
    AVCodec *avcodec = avcodec_find_decoder(in_stream->codecpar->codec_id);
42.  
    AVStream *out_stream = avformat_new_stream(ofmt_ctx, avcodec);
43.  
    videoindex_v = i;
44.  
    if (!out_stream) {
45.  
    printf("Failed allocating output stream\n");
46.  
    ret = AVERROR_UNKNOWN;
47.  
    goto end;
48.  
    }
49.  
    videoindex_out = out_stream->index;
50.  
    AVCodecContext *codec_ctx = avcodec_alloc_context3(avcodec);
51.  
    ret = avcodec_parameters_to_context(codec_ctx, in_stream->codecpar);
52.  
    if (ret < 0) {
53.  
    printf("Failed to copy context from input to output stream codec context\n");
54.  
    goto end;
55.  
    }
56.  
    codec_ctx->codec_tag = 0;
57.  
    if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
58.  
    codec_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
59.  
     
60.  
    ret = avcodec_parameters_from_context(out_stream->codecpar, codec_ctx);
61.  
    int q = 0;
62.  
    }
63.  
    }
64.  
     
65.  
    4、获取音频流信息并拷贝相应编码格式
66.  
    for (i = 0; i < ifmt_ctx_a->nb_streams; i++) {
67.  
    if (ifmt_ctx_a->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
68.  
    AVStream *in_stream = ifmt_ctx_a->streams[i];
69.  
    AVCodec *avcodec = avcodec_find_decoder(in_stream->codecpar->codec_id);
70.  
    AVStream *out_stream = avformat_new_stream(ofmt_ctx, avcodec);
71.  
    audioindex_a = i;
72.  
    if (!out_stream) {
73.  
    printf("Failed allocating output stream\n");
74.  
    ret = AVERROR_UNKNOWN;
75.  
    goto end;
76.  
    }
77.  
    audioindex_out = out_stream->index;
78.  
    avcodec = avcodec_find_decoder(in_stream->codecpar->codec_id);
79.  
     
80.  
    avcodec_parameters_copy(absCtx->par_in, in_stream->codecpar);
81.  
    av_bsf_init(absCtx);
82.  
     
83.  
    AVCodecContext *codec_ctx = avcodec_alloc_context3(avcodec);
84.  
    ret = avcodec_parameters_to_context(codec_ctx, in_stream->codecpar);
85.  
    if (ret < 0) {
86.  
    printf("Failed to copy context from input to output stream codec context\n");
87.  
    goto end;
88.  
    }
89.  
    codec_ctx->codec_tag = 0;
90.  
    if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
91.  
    codec_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
92.  
     
93.  
    ret = avcodec_parameters_from_context(out_stream->codecpar, codec_ctx);
94.  
    out_stream->codecpar->extradata = (uint8_t*)av_malloc(2);
95.  
    out_stream->codecpar->extradata_size = 2;
96.  
    unsigned char dsi1[2];
97.  
    unsigned int sampling_frequency_index = (unsigned int)get_sr_index(8000);
98.  
    make_dsi(sampling_frequency_index, 1, dsi1);
99.  
    memcpy(out_stream->codecpar->extradata, dsi1, 2);
100.  
      
101.  
     break;
102.  
     }
103.  
     }
104.  
     5、打开MP4文件
105.  
     if (!(ofmt->flags & AVFMT_NOFILE)) {
106.  
     if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE) < 0) {
107.  
     printf("Could not open output file '%s'", out_filename);
108.  
     goto end;
109.  
     }
110.  
     }
111.  
     6、设置字典fmp4的关键
112.  
     AVDictionary *movflags = nullptr;
113.  
     const bool low_delay = true;
114.  
     if (low_delay) {
115.  
     // In case of low delay, set fragment duration to 200 ms.
116.  
     av_dict_set(&movflags, "movflags", "empty_moov+default_base_moof", 0);
117.  
     av_dict_set_int(&movflags, "frag_duration", 200 * 1000, 0);
118.  
     }
119.  
     else {
120.  
     // Only produce fragment until we have next key frame.
121.  
     av_dict_set(&movflags, "movflags", "empty_moov+default_base_moof+frag_keyframe", 0);
122.  
     }
123.  
     //avformat_open_input(&addofmt_ctx, addinputAacFileName, 0, &movflags);
124.  
     ret = avformat_write_header(ofmt_ctx, &movflags);
125.  
     if (ret < 0) {
126.  
     fprintf(stderr, "Error occurred when opening output file\n");
127.  
     goto end;
128.  
     }
129.  
     7、打包
130.  
      
131.  
     if ((ret = av_interleaved_write_frame(ofmt_ctx, &pkt)) < 0) {
132.  
     printf("Error muxing packet\n");
133.  
     break;
134.  
     }

具体工程参考：https://download.csdn.net/download/venice0708/11434379