if (fmt_ctx->nb_streams > nb_streams) {
#define REALLOCZ_ARRAY_STREAM (ptr, cur_n, new_n)                      \
{                                                                      \
    ret = av_reallocp_array(&(ptr), (new_n), sizeof(*(ptr)));          \
    if( ret < 0)                                                       \
        goto end;                                                      \
    memset( (ptr) + (cur_n), 0, (new_n) - (cur_n) * sizeof(*(ptr)) )   \
}
            REALLOCZ_ARRAY_STREAM(nb_streams_frames, nb_streams, fmt_ctx->nb_streams);
            REALLOCZ_ARRAY_STREAM(nb_streams_packets,fmt_ctx->nb_streams);
            REALLOCZ_ARRAY_STREAM(selected_streams,fmt_ctx->nb_streams);
            nb_streams = fmt_ctx->nb_streams;
        }