事实上你需要的是先用 http 源，然后安装 apt-transport-https，这之后就可以改用 https 源了。
出现这样的问题是因为 Debian 的 apt 默认没有 https 支持的原因

如果是多条音轨的话在 MKVToolNix 里就会显示成多条音轨的，如果你只看到一条的话那就是本来就混在一起分不开了。

用 where 命令看看有没有同名的可执行的东西吧

@codechaser
Appendix C (C++11, C.1.2)

“ Change: A name of file scope that is explicitly declared const, and not explicitly declared extern, has internal linkage, while in C it would have external linkage

Rationale: Because const objects can be used as compile-time values in C++, this feature urges programmers to provide explicit initializer values for each const. This feature allows the user to put const objects in header files that are included in many compilation units.”