trak box的解析

常见的MP4结构图

trak box的定义

/* ** trak box的定义，包含： ** tkhd、mdia */  static mp4_atom_handler mp4_trak_atoms[] = {      { "tkhd", &Mp4Meta::mp4_read_tkhd_atom },      { "mdia", &Mp4Meta::mp4_read_mdia_atom },      { NULL, NULL }  }; 
trak box的解析
// 读取trak boxintMp4Meta::mp4_read_trak_atom(int64_t atom_header_size, int64_t atom_data_size){    int             rc;    Mp4Trak         *trak;    if (trak_num >= MP4_MAX_TRAK_NUM - 1)        return -1;    trak = new Mp4Trak();    trak_vec[trak_num++] = trak;    trak->trak_atom.buffer = TSIOBufferCreate();    trak->trak_atom.reader = TSIOBufferReaderAlloc(trak->trak_atom.buffer);    TSIOBufferCopy(trak->trak_atom.buffer, meta_reader, atom_header_size, 0);    mp4_meta_consume(atom_header_size);	// 该函数内部实际会进行下面的处理：	// 调用mp4_read_tkhd_atom读取tkhd box	// 调用mp4_read_mdia_atom读取mdia box    rc = mp4_read_atom(mp4_trak_atoms, atom_data_size);    return rc;}