我很少摆弄我高效的 debian 8 系统，所以我不记得这个问题是何时或如何引入的。我在尝试安装openshot并获得未满足的依赖项时注意到了这一点（最后输出，因为我的问题似乎更深入）。
我这样做了apt-get update，它像往常一样工作，没有警告或错误。但apt-get upgrade报道称：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
librtmp1
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
为什么要退缩？试apt-get install librtmp1：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
librtmp1 : Depends: libgnutls30 (>= 3.5.6) but it is not installable
Depends: libhogweed4 but it is not installable
Depends: libnettle6 but it is not installable
E: Unable to correct problems, you have held broken packages.
“无法安装”听起来很糟糕。但我无法删除它，因为（直接或间接）依赖于它的软件包中有 cmake、libre-office 和 kde-runtime（以及 Blender、gimp、qemu 等）等基础知识。
一些帖子建议这样做apt-get dist-upgrade，但这没有任何作用：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
在我的手动修复尝试中，还有一个奇怪的观察结果，apt-get install python-mlt它涉及到 libstdc++6 的非常基本的冲突：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
python-mlt : Depends: libmlt++3 (>= 1:6.4.1) but it is not going to be installed
Depends: libmlt6 (>= 1:6.4.1) but it is not going to be installed
Depends: libstdc++6 (>= 5) but 4.9.2-10 is to be installed
E: Unable to correct problems, you have held broken packages.
更新：/etc/apt/sources.list：
deb [arch=amd64,i386] http://ftp.de.debian.org/debian jessie main contrib non-free
deb-src http://ftp.de.debian.org/debian/ jessie main
deb [arch=amd64,i386] http://ftp2.de.debian.org/debian jessie-backports main
deb-src http://ftp2.de.debian.org/debian jessie-backports main
deb http://www.deb-multimedia.org testing main non-free
我不记得多媒体测试是什么时候开始的......
答案1
编辑您的sources.list，替换testing为jessie然后运行：
apt-get update
apt-get upgrade
pt-get install python-mlt