由于Ubuntu18.04中安装gstreamer的版本默认为1.14，在QGC的rtsp视频显示中有问题，所以需要对gstreamer进行升级，查询后：
在Linux（UButun）和Windows编译GStreamer 过程 - 知乎
可以直接下载1.19版本的进行编译安装，meson build后出现提示：
The Meson build system
Version: 0.45.1
Source dir: /home/cubar/code/gstreamer/gst-build
Build dir: /home/cubar/code/gstreamer/gst-build/build
Build type: native build
meson.build:87:15: ERROR: lexer
['gstreamer', {'build-hotdoc': true}],网上查询没有结果，最后 考虑是不是版本问题，通过meson -v查看
meson -v
0.45.1
由于我使用的是sudo apt-get install meson命令进行安装的，版本太低了，删除后使用 pip3 install meson安装，结果：
meson -v
0.61.4
这个时候，再meson build就正常了!
meson build
The Meson build system
Version: 0.61.4
Source dir: /home/***/code/gstreamer/gst-build
Build dir: /home/***/code/gstreamer/gst-build/build
Build type: native build
Project name: All GStreamer modules
Project version: 1.19.2
C compiler for the host machine: cc (gcc 7.5.0 "cc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0")
C linker for the host machine: cc ld.bfd 2.30
Host machine cpu family: x86_64
Host machine cpu: x86_64
meson.build:9: WARNING:
======================================================================================================
gst-build is now obsolete and has now been moved into the GStreamer monorepo, see
https://gstreamer.freedesktop.org/documentation/frequently-asked-questions/mono-repository.html
for more details.
======================================================================================================
Program python3 found: YES (/usr/bin/python3)
WARNING: Python files installed by Meson might not be found by python interpreter.
This warning can be avoided by setting "python.platlibdir" option.
WARNING: Python files installed by Meson might not be found by python interpreter.
This warning can be avoided by setting "python.purelibdir" option.
WARNING: You should add the boolean check kwarg to the run_command call.
It currently defaults to false,
but it will default to true in future releases of meson.
See also: https://github.com/mesonbuild/meson/issues/9300
Executing subproject orc
orc| Project name: orc
orc| Project version: 0.4.32
orc| C compiler for the host machine: cc (gcc 7.5.0 "cc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0")
orc| C linker for the host machine: cc ld.bfd 2.30
orc| Compiler for C supports link arguments -Wl,-Bsymbolic-functions: YES
orc| Compiler for C supports arguments -fvisibility=hidden: YES
orc| Run-time dependency threads found: YES
orc| Library m found: YES
orc| Checking for function "clock_gettime" : YES
orc| Header <android/log.h> has symbol "__android_log_print" : NO
orc| Checking for function "gettimeofday" : YES
orc| Checking for function "posix_memalign" : YES
orc| Checking for function "mmap" : YES
orc| Checking for function "pthread_jit_write_protect_np" : NO
orc| Has header "sys/time.h" : YES
orc| Has header "unistd.h" : YES
orc| Has header "valgrind/valgrind.h" : NO
...................
