在jetson nano上尝试用python调用.so文件，但是报错，报错信息显示是opencv出现问题，遂决定重装opencv。先是编译opencv 3.4.10，报错，后面又重装之前的opencv 4.1.1，居然依旧报错。遂记录。

1. 报错

无论是opencv的3.4.10还是4.1.1，均报同样的错，所以肯定不是opencv的问题。

报错如下

/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp:585:34: error: ‘AVStream {aka struct AVStream}’ has no member named ‘codec’
         avcodec_close( video_st->codec );
                                  ^~~~~
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp: At global scope:
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp:775:39: error: ‘AVLockOp’ has not been declared
 static int LockCallBack(void **mutex, AVLockOp op)
                                       ^~~~~~~~
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp: In function ‘int LockCallBack(void**, int)’:
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp:780:14: error: ‘AV_LOCK_CREATE’ was not declared in this scope
         case AV_LOCK_CREATE:
              ^~~~~~~~~~~~~~
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp:780:14: note: suggested alternative: ‘AV_LOG_TRACE’
         case AV_LOCK_CREATE:
              ^~~~~~~~~~~~~~
              AV_LOG_TRACE
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp:789:14: error: ‘AV_LOCK_OBTAIN’ was not declared in this scope
         case AV_LOCK_OBTAIN:
              ^~~~~~~~~~~~~~
/opt/opencv4/opencv-4.1.1/modules/videoio/src/cap_ffmpeg_impl.hpp:789:14: note: suggested alternative: ‘CLOCK_TAI’
         case AV_LOCK_OBTAIN:
              ^~~~~~~~~~~~~~
              CLOCK_TAI
...

报错信息还有很多，但是均指向同一个文件modules/videoio/src/cap_ffmpeg_impl.hpp，考虑ffmpeg出现问题。

2. 报错原因

参考opencv官方论坛上的回答


报错原因为ffmpeg版本过高，解决方法为安装ffmpeg 4.4及以前版本。

3. 卸载当前ffmpeg

参考博客《Ubuntu16.04卸载旧的ffmpeg安装新的ffmpeg》

3.1. 卸载apt安装的ffmpeg

如果用apt-get install ffmpeg安装的，使用以下命令卸载

sudo apt-get --purge remove ffmpeg
sudo apt-get --purge autoremove

3.2. 卸载编译安装的ffmpeg

以ffmpeg-4.1为例，进入ffmpeg安装目录，如下

cd ffmpeg-4.1
make uninstall  ##删除由make install命令安装的文件
make clean  ##只删除make时产生的临时文件
make distclean  ##同时删除configure和make产生的临时文件

4. 编译安装ffmpeg 4.3

参考博客《Jetson 环境安装(三):jetson nano配置ffmpeg和nginx(亲测)》

4.1. 下载安装包

这里，我把安装包下载在~/Downloads/路径下，并解压

wget http://www.ffmpeg.org/releases/ffmpeg-4.3.tar.gz
tar -zxvf ffmpeg-4.3.tar.gz

4.2. 安装依赖

如下

sudo apt-get install -y nasm yasm cmake mercurial
sudo apt-get install -y libxcb-xfixes0-dev pkg-config texinfo wget zlib1g-dev
sudo apt-get install -y libtool libva-dev libvdpau-dev libvorbis-dev libxcb1-dev libxcb-shm0-dev
sudo apt-get install -y libfreetype6-dev libsdl2-dev libtheora-dev
sudo apt-get install -y autoconf automake build-essential git libass-dev
sudo apt-get install libx264-dev
sudo apt-get install libx265-dev libnuma-dev
sudo apt-get install libvpx-dev

注意，如果安装报错，考虑更换源，我的源如下

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb http://mirrors.ustc.edu.cn/ubuntu-ports bionic main restricted universe multiverse
# deb-src http://mirrors.ustc.edu.cn/ubuntu-ports bionic main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports bionic-updates main restricted universe multiverse
# deb-src http://mirrors.ustc.edu.cn/ubuntu-ports bionic-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports bionic-backports main restricted universe multiverse
# deb-src http://mirrors.ustc.edu.cn/ubuntu-ports bionic-backports main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu-ports bionic-security main restricted universe multiverse
# deb-src http://mirrors.ustc.edu.cn/ubuntu-ports bionic-security main restricted universe multiverse


# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse

# 预发布软件源，不建议启用
# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.aliyun.com/ubuntu-ports/ bionic main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu-ports/ bionic main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu-ports/ bionic-updates main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu-ports/ bionic-updates main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu-ports/ bionic-backports main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu-ports/s bionic-backports main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu-ports/ bionic-security main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu-ports/ bionic-security main restricted universe multiverse

# 预发布软件源，不建议启用
# deb https://mirrors.aliyun.com/ubuntu-ports/ bionic-proposed main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu-ports/ bionic-proposed main restricted universe multiverse

deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial main multiverse restricted universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-security main multiverse restricted universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-updates main multiverse restricted universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-backports main multiverse restricted universe
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial main multiverse restricted universe
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-security main multiverse restricted universe
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-updates main multiverse restricted universe
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ xenial-backports main multiverse restricted universe

4.3. 编译安装

这里，我们把~/Downloads/中已经解压的ffmpeg-4.3文件夹移入到/opt/路径下

cd ~/Downloads
sudo mv -f ffmpeg-4.3 /opt/

然后进入ffmpeg-4.3，编译

cd /opt/ffmpeg-4.3
sudo ./configure --enable-shared   --enable-libx264  --enable-gpl --enable-libx265  --prefix=/usr/local/ffmpeg
sudo make && sudo make install

然后配置全局环境变量

sudo vim /etc/profile

在最后加入

export FFMPEG_HOME=/usr/local/ffmpeg
export PATH=$FFMPEG_HOME/bin:$PATH

保存，退出，并输入

source /etc/profile

将ffmpeg添加进动态库目录，如下

sudo vim /etc/ld.so.conf.d/ffmpeg.conf 

添加如下内容

/usr/local/ffmpeg/lib

配置生效

ldconfig

4.4. 测试ffmpeg

ffmpeg -version

输出如下内容即可

5. 编译安装opencv 4.1.1

参考博客《jetson nano和jetson nx 重装opencv（opencv4.1.1+opencv-contrib安装）》