君正T41交叉编译ffmpeg、opencv并做h264软解，利用君正SDK做h264硬件编码

1 交叉编译ffmpeg----错误解决过程，不要看

1.1 下载源码

1.2 配置

1.3 编译安装

1.3.1 报错：libavfilter/libavfilter.so: undefined reference to `fminf'

1.3.2 报错：error: unknown type name 'HEVCContext'; did you mean 'HEVCPredContext'?

2 交叉编译opencv----错误解决过程，不要看了，直接看目录3

2.1 下载源码

2.2 修改mips.toolchain.cmake

2.3 配置

2.3.1 报错：can’t find ffmpeg – ‘pkg-config’ utility is missing

2.4 编译、安装

2.4.1编译报错：fatal error: zlib.h: No such file or directory

2.4.2 报错：undefined reference to `avcodec_find_encoder@LIBAVCODEC_57

2.4.3最终使用的cmake命令

2.4.4 编译出来的库是x86的

2.4.5 undefined reference to `avcodec_find_encoder@LIBAVCODEC_57----为什么这个错误又出现了

2.5 换个新的xshell终端做实验

3 交叉编译opencv----整理后的正确步骤,直接看这个

3.1 下载源码

3.2 修改../platforms/linux/mips.toolchain.cmake和../platforms/linux/mips32r5el-gnu.toolchain.cmake

3.3 配置PKG_CONFIG_LIBDIR

3.4 cmake

3.5 编译、安装

4 软件解码

4.1 libopencv_core.so: undefined reference to `__atomic_compare_exchange_8'

4.2 illegal instruction

4.3 错误： CAP_IMAGES: Stop scanning. Can't read image file

5 交叉编译ffmepg----正确步骤，直接看这个

5.1 下载源码

5.2 配置

5.3 编译、安装

参考文献：

君正T41芯片只有编码器没有解码器，所以需要用软件解码对h264进行解码，试一下ffmpeg和opencv。

1 交叉编译ffmpeg----错误解决过程，不要看

1.1 下载源码

Index of /releases

不需要用特别新的，我这里下载4.1.3的版本就行，然后解压

tar xzvf ffmpeg-4.1.3.tar.gz 
cd ffmpeg-4.1.3/
mkdir install

1.2 配置

./configure --enable-cross-compile --cross-prefix=mips-linux-uclibc- --arch=mips --target-os=linux --cc=mips-linux-uclibc-gcc --prefix=$PWD/install --enable-shared --enable-pic --disable-static --enable-gpl --enable-nonfree --enable-pthreads --enable-ffmpeg --disable-ffplay --enable-swscale --enable-mips32r2  --disable-mipsdsp1 --disable-mipsdspr2 --disable-mips32r1 --disable-mipsfpu  --disable-mips64r2  --disable-mips32r6

1.3 编译安装

make -j
make install

编译报错

1.3.1 报错：libavfilter/libavfilter.so: undefined reference to `fminf'

libavfilter/libavfilter.so: undefined reference to `fminf'
libavfilter/libavfilter.so: undefined reference to `fmaxf'

从这篇博客看海思3516ev200 _FFMPEG库编译_ffmpeg undefined reference to `fmaxf-CSDN博客

然后从博客的评论区看

行吧，应该是我的交叉编译工具链的问题，重新下载3.3.9的，然后重新重复上面的过程。

然后又报错

1.3.2 报错：error: unknown type name 'HEVCContext'; did you mean 'HEVCPredContext'?

libavcodec/mips/hevcpred_msa.c:1913:32: error: unknown type name 'HEVCContext'; did you mean 'HEVCPredContext'?
 void ff_intra_pred_8_16x16_msa(HEVCContext *s, int x0, int y0, int c_idx)
                                ^~~~~~~~~~~
                                HEVCPredContext
libavcodec/mips/hevcpred_msa.c:2426:32: error: unknown type name 'HEVCContext'; did you mean 'HEVCPredContext'?
 void ff_intra_pred_8_32x32_msa(HEVCContext *s, int x0, int y0, int c_idx)
                                ^~~~~~~~~~~
                                HEVCPredContext

好吧，直接vscode把整个ffmpeg代码打开看看怎么个事，查找HEVCContext的定义，

发现在ffmpeg-3.3.9/libavcodec/hevcpred.h中有

然后在ffmpeg-3.3.9/libavcodec/hevcdec.h中有

那么在ffmpeg-3.3.9/libavcodec/mips/hevcpred_msa.c中添加

//#include "libavcodec/hevcpred.h"  //添加了这一行没用，还是报错
#include "libavcodec/hevcdec.h"

然后make install之后发现

先这样，后面再看库能不能用。

2 交叉编译opencv----错误解决过程，不要看了，直接看目录3

2.1 下载源码

首先也还是下载opencv源码Releases - OpenCV，然后

2.2 修改mips.toolchain.cmake

cd opencv-3.4.9/
mkdir build
mkdir install
cd platforms/linux/

mips.toolchain.cmake本来内容如下

# ----------------------------------------------------------------------------------------------
#  MIPS ToolChanin can be downloaded from https://www.mips.com/develop/tools/codescape-mips-sdk/ .
#  Toolchains with 'mti' in the name (and install directory) are for MIPS R2-R5 instruction sets.
#  Toolchains with 'img' in the name are for MIPS R6 instruction sets.
#  It is recommended to use cmake-gui application for build scripts configuration and generation:
#  1. Run cmake-gui
#  2. Specifiy toolchain file for cross-compiling, mips32r5el-gnu.toolchian.cmake or mips64r6el-gnu.toolchain.cmake
#     can be selected.
#  3. Configure and Generate makefiles.
#  4. make -j4 & make install
# ----------------------------------------------------------------------------------------------

if(COMMAND toolchain_save_config)
  return() # prevent recursive call
endif()

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
if(NOT DEFINED CMAKE_SYSTEM_PROCESSOR)
  set(CMAKE_SYSTEM_PROCESSOR mips)
endif()

include("${CMAKE_CURRENT_LIST_DIR}/gnu.toolchain.cmake")

if(CMAKE_SYSTEM_PROCESSOR STREQUAL mips AND NOT MIPS_IGNORE_FP)
  set(FLOAT_ABI_SUFFIX "")
endif()

if(NOT "x${GCC_COMPILER_VERSION}" STREQUAL "x")
  set(__GCC_VER_SUFFIX "-${GCC_COMPILER_VERSION}")
endif()

if(NOT DEFINED CMAKE_C_COMPILER)
  find_program(CMAKE_C_COMPILER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-gcc${__GCC_VER_SUFFIX})
endif()
if(NOT DEFINED CMAKE_CXX_COMPILER)
  find_program(CMAKE_CXX_COMPILER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-g++${__GCC_VER_SUFFIX})
endif()
if(NOT DEFINED CMAKE_LINKER)
  find_program(CMAKE_LINKER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ld${__GCC_VER_SUFFIX} ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ld)
endif()
if(NOT DEFINED CMAKE_AR)
  find_program(CMAKE_AR NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ar${__GCC_VER_SUFFIX} ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ar)
endif()

if(NOT DEFINED MIPS_LINUX_SYSROOT AND DEFINED GNU_MACHINE)
  set(MIPS_LINUX_SYSROOT /usr/bin)
endif()

if(NOT DEFINED CMAKE_CXX_FLAGS)
  if(CMAKE_SYSTEM_PROCESSOR MATCHES "mips32r5el")
    set(CMAKE_C_FLAGS             "-march=mips32r5 -EL -mmsa -mhard-float -mfp64 -mnan=2008 -mabs=2008 -O3 -ffp-contract=off -mtune=p5600" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-march=mips32r5 -EL -mmsa -mhard-float -mfp64 -mnan=2008 -mabs=2008 -O3 -ffp-contract=off -mtune=p5600" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl -latomic" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "mips64r6el")
    set(CMAKE_C_FLAGS             "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
  endif()
  set(CMAKE_SHARED_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_SHARED_LINKER_FLAGS}")
  set(CMAKE_MODULE_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_MODULE_LINKER_FLAGS}")
  set(CMAKE_EXE_LINKER_FLAGS    "${MIPS_LINKER_FLAGS} ${CMAKE_EXE_LINKER_FLAGS}")
endif()

set(CMAKE_FIND_ROOT_PATH ${CMAKE_FIND_ROOT_PATH} ${MIPS_LINUX_SYSROOT})

set(TOOLCHAIN_CONFIG_VARS ${TOOLCHAIN_CONFIG_VARS}
    MIPS_LINUX_SYSROOT
)
toolchain_save_config()

修改成下面的形式

# ----------------------------------------------------------------------------------------------
# MIPS ToolChain can be downloaded from https://www.mips.com/develop/tools/codescape-mips-sdk/ .
# Toolchains with 'mti' in the name (and install directory) are for MIPS R2-R5 instruction sets.
# Toolchains with 'img' in the name are for MIPS R6 instruction sets.
# It is recommended to use cmake-gui application for build scripts configuration and generation:
# 1. Run cmake-gui
# 2. Specify toolchain file for cross-compiling, mips32r5el-gnu.toolchian.cmake or mips64r6el-gnu.toolchain.cmake
#    can be selected.
# 3. Configure and Generate makefiles.
# 4. make -j4 & make install
# ----------------------------------------------------------------------------------------------

if(COMMAND toolchain_save_config)
  return() # prevent recursive call
endif()

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
if(NOT DEFINED CMAKE_SYSTEM_PROCESSOR)
  set(CMAKE_SYSTEM_PROCESSOR mips)
endif()

include("${CMAKE_CURRENT_LIST_DIR}/gnu.toolchain.cmake")

if(CMAKE_SYSTEM_PROCESSOR STREQUAL mips AND NOT MIPS_IGNORE_FP)
  set(FLOAT_ABI_SUFFIX "")
endif()

if(NOT "x${GCC_COMPILER_VERSION}" STREQUAL "x")
  set(__GCC_VER_SUFFIX "-${GCC_COMPILER_VERSION}")
endif()

# Set GNU_MACHINE based on your toolchain prefix
set(GNU_MACHINE "mips-linux-uclibc-")

# Define paths to the compilers using the GNU_MACHINE variable and your toolchain path
if(NOT DEFINED CMAKE_C_COMPILER)
  find_program(CMAKE_C_COMPILER NAMES ${GNU_MACHINE}gcc${__GCC_VER_SUFFIX}
               PATHS /data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/bin/
               NO_DEFAULT_PATH)
endif()
if(NOT DEFINED CMAKE_CXX_COMPILER)
  find_program(CMAKE_CXX_COMPILER NAMES ${GNU_MACHINE}g++${__GCC_VER_SUFFIX}
               PATHS /data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/bin/
               NO_DEFAULT_PATH)
endif()
if(NOT DEFINED CMAKE_LINKER)
  find_program(CMAKE_LINKER NAMES ${GNU_MACHINE}ld${__GCC_VER_SUFFIX}
               PATHS /data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/bin/
               NO_DEFAULT_PATH)
endif()
if(NOT DEFINED CMAKE_AR)
  find_program(CMAKE_AR NAMES ${GNU_MACHINE}ar${__GCC_VER_SUFFIX}
               PATHS /data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/bin/
               NO_DEFAULT_PATH)
endif()

# Set the sysroot if it's not defined already
if(NOT DEFINED MIPS_LINUX_SYSROOT)
  set(MIPS_LINUX_SYSROOT /data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/sysroot/)
endif()

# Add your specific compiler flags here
if(NOT DEFINED CMAKE_CXX_FLAGS)
  if(CMAKE_SYSTEM_PROCESSOR MATCHES "mips32r5el")
    set(CMAKE_C_FLAGS             "-march=mips32r5 -EL -mmsa -mhard-float -mfp64 -mnan=2008 -mabs=2008 -O3 -ffp-contract=off -mtune=p5600" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-march=mips32r5 -EL -mmsa -mhard-float -mfp64 -mnan=2008 -mabs=2008 -O3 -ffp-contract=off -mtune=p5600" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl -latomic" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "mips64r6el")
    set(CMAKE_C_FLAGS             "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
  endif()
  set(CMAKE_SHARED_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_SHARED_LINKER_FLAGS}")
  set(CMAKE_MODULE_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_MODULE_LINKER_FLAGS}")
  set(CMAKE_EXE_LINKER_FLAGS    "${MIPS_LINKER_FLAGS} ${CMAKE_EXE_LINKER_FLAGS}")
endif()

set(CMAKE_FIND_ROOT_PATH ${CMAKE_FIND_ROOT_PATH} ${MIPS_LINUX_SYSROOT})

set(TOOLCHAIN_CONFIG_VARS ${TOOLCHAIN_CONFIG_VARS}
    MIPS_LINUX_SYSROOT
)
toolchain_save_config()

2.3 配置

cd ../../build   先退到opencv路径再创建build和install，不要在platforms/linux目录下创建

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF - ..

配置后发现ffmpeg并没有找到

2.3.1 报错：can’t find ffmpeg – ‘pkg-config’ utility is missing

然后执行下面这一行

export PKG_CONFIG_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/pkgconfig:$PKG_CONFIG_PATH

然后继续config

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF ..

然后看到这这篇博客：OpenCV+FFmpeg交叉编译_opencv ffmpeg-CSDN博客

上面说原因是ffmpeg test code没有编译成功然后HAVE_FFMPEG被置为了OFF。

然后我在我的日志中搜test code果然发现了

看opencv-3.4.9/cmake/OpenCVFindLibsVideo.cmake

他的博客上说直接注释掉下面的内容，但其实不应该这么做。

因为注释掉之后发现为什么最后一个还是NO，

这里最后一个为什么还是NO，是因为ffmpeg中库libavresample改名为libswresample.so了，所以opencv找不到，其实修改 opencv-3.4.9/cmake/OpenCVFindLibsVideo.cmake中

就可以了，也就是让opencv去找libswresample这个库。

所以就都找到了，不需要像那篇博客上说的那样把内容注释掉，而是修改库的名字就可以了，

2.4 编译、安装

make -j8
make install

2.4.1编译报错：fatal error: zlib.h: No such file or directory

好吧，服了，这破东西，这是找不到zlib，处理png的图片时候需要用zlib，那么根据我之前交叉编译opencv时候cmake-gui的提示：ubuntu交叉编译opencv-CSDN博客

那次是用的cmake-gui，那么这次我在cmake中增加相应的配置， cmake命令中增加zlib的-DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib，然后重新配置，重新编译。

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF -DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib ..

2.4.2 报错：undefined reference to `avcodec_find_encoder@LIBAVCODEC_57

./../lib/libopencv_videoio.so.3.4.9: undefined reference to `avcodec_find_encoder@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `sws_getContext@LIBSWSCALE_4'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_frame_unref@LIBAVUTIL_55'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_write_frame@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_log_set_level@LIBAVUTIL_55'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avformat_close_input@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_bitstream_filter_init@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avformat_get_riff_video_tags@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avcodec_get_context_defaults3@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avcodec_decode_video2@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_lockmgr_register@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `sws_freeContext@LIBSWSCALE_4'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_bitstream_filter_filter@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_malloc@LIBAVUTIL_55'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_read_frame@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avformat_alloc_context@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avformat_network_init@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_guess_sample_aspect_ratio@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_image_get_buffer_size@LIBAVUTIL_55'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `avcodec_flush_buffers@LIBAVCODEC_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_write_trailer@LIBAVFORMAT_57'
../../lib/libopencv_videoio.so.3.4.9: undefined reference to `av_dict_set@LIBAVUTI

好吧，这破东西是找不到库，直接在opencv-3.4.9/CMakeLists.txt中增加

link_directories("/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib")

然后还是重新直接cmake，然后make，还是报错，说明这个方法不行。

然后google搜索交叉编译x264 ffmpeg opencv 关键字，看到了这篇博客：Linux aarch64-linux-gnu-交叉编译x264、ffmpeg、opencv并移植-CSDN博客

它里面有这个

行，那我也试一下，然后也不行，然后总之我又中查找，发现了这个命令可以用，

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF -DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib -DFFMPEG_LIBRARIES=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/ -DFFMPEG_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/ -DFFMPEG_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/include -DCMAKE_PREFIX_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/ ..

但是我觉得虽然问题解决了，我还不知道哪一条起作用的，所以我做了下面的几个实验。

2.4.3最终使用的cmake命令

cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF -DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib -DFFMPEG_LIBRARIES=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/ -DFFMPEG_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/include -DCMAKE_PREFIX_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/ ..

然后直接 make -j; make install就可以了。编译出来之后，发现

file libopencv_videostab.so.3.4.9
libopencv_videostab.so.3.4.9: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, BuildID[sha1]=0b27b56ce5c93949283722a2b136399ebfa933dd, with debug_info, not stripped

这怎么是x86的。。。。。

2.4.4 编译出来的库是x86的

针对编译出来的库是x86，那我觉得大概率是toolchain那个脚本不对，于是这次我只修改上层的opencv-3.4.9/platforms/linux/mips32r5el-gnu.toolchain.cmake 在里面增加交叉编译工具链的路径

set(CMAKE_SYSTEM_PROCESSOR mips32r5el)
set(GCC_COMPILER_VERSION "" CACHE STRING "GCC Compiler version")
set(GNU_MACHINE "/data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/bin/mips-linux-uclibc" CACHE STRING "GNU compiler triple")

include("${CMAKE_CURRENT_LIST_DIR}/mips.toolchain.cmake")

其实是类似的，可以看到opencv-3.4.9/platforms/linux/mips32r5el-gnu.toolchain.cmake里面包含了 include("${CMAKE_CURRENT_LIST_DIR}/mips.toolchain.cmake")，

然后opencv-3.4.9/platforms/linux/mips.toolchain.cmake内容也修改成mips32r2，因为我用的君正的是mips32r2的指令集。

然后make -j; make instll就可以了。然后file ../install/lib/libopencv_photo.so.3.4.9
../install/lib/libopencv_photo.so.3.4.9: ELF 32-bit LSB shared object, MIPS, MIPS32 rel2 version 1 (SYSV), dynamically linked, with debug_info, not stripped

发现可以了，是mips的了。

2.4.5 undefined reference to `avcodec_find_encoder@LIBAVCODEC_57----为什么这个错误又出现了

当我编译完成之后，我想把步骤重新来一遍，然后按照上面的步骤又试了下，然后发现这种找不到ffmpeg的错误又来了，不行，必须找到根本原因。然后我发现一个奇怪的现象

 2424  mv opencv-3.4.9 correct_backup_opencv-3.4.9
 2425  unzip opencv-3.4.9.zip 
 2426  cd opencv-3.4.9/
 2427  ll
 2428  mkdir build
 2429  mkdir install
 2430  cd build
 2431  export PKG_CONFIG_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/pkgconfig:$PKG_CONFIG_PATH
 2432  cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips32r5el-gnu.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF -DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib -DFFMPEG_LIBRARIES=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/ -DFFMPEG_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/include -DCMAKE_PREFIX_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/ ..
 2433  make -j
 2434  export PKG_CONFIG_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/pkgconfig:$PKG_CONFIG_PATH
 2435  make -j
 2436  make clean
 2437  cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips32r5el-gnu.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DSOFTFP=ON -DENABLE_PROFILING=OFF -DWITH_OPENCL=OFF -DWITH_TBB=ON -DWITH_V4L=ON -DHAVE_CAMV4L2=ON -DBUILD_TESTS=OFF -DINSTALL_PYTHON_EXAMPLES=OFF -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_opencv_js=OFF -DENABLE_NEON=OFF -DENABLE_VFPV3=OFF -DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib -DFFMPEG_LIBRARIES=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/ -DFFMPEG_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/include -DCMAKE_PREFIX_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/ ..
 2438  export PKG_CONFIG_PATH=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.3.9/install/lib/pkgconfig:$PKG_CONFIG_PATH
 2439  make -j
 2440  history]
 2441  history

我发现我的命令都是一样的，但是执行2433的make -j的时候报错，但是当我2439的那次make -j发现并不报错了，前后两次的命令一模一样的呀，那么为什么，一定是哪里做错了，我反复试了几次，有时候成功，有时候报错，那么问题在哪里，问题到了这里已经有些离谱了，这时候感觉是我的服务器环境有问题了。。。。。。。。。。。。需要把当前的xshell终端给关了，重新打开一个继续做实验。

2.5 换个新的xshell终端做实验

换个新的xshell终端，然后把之前的opencv删掉，重新unzip一个，然后做实验。

实验过程不写了，直接把正确步骤写到下面正确步骤的目录.

3 交叉编译opencv----整理后的正确步骤,直接看这个

3.1 下载源码

首先也还是下载opencv源码Releases - OpenCV，

unzip opencv-3.4.9.zip
cd opencv-3.4.9/
mkdir build
mkdir install

3.2 修改../platforms/linux/mips.toolchain.cmake和../platforms/linux/mips32r5el-gnu.toolchain.cmake

修改../platforms/linux/mips32r5el-gnu.toolchain.cmake在里面添加上交叉编译工具链的路径

set(CMAKE_SYSTEM_PROCESSOR mips32r5el)
set(GCC_COMPILER_VERSION "" CACHE STRING "GCC Compiler version")
set(GNU_MACHINE "/data3/t41_toolchain/mips-gcc720-uclibc0.9.33.2-r5.1.4/bin/mips-linux-uclibc" CACHE STRING "GNU compiler triple")

include("${CMAKE_CURRENT_LIST_DIR}/mips.toolchain.cmake")

因为我用的君正t41是mips32r2指令集的，所以修改../platforms/linux/mips.toolchain.cmake(这个不是mips32r5el-gnu.toolchain.cmake，mips32r5el-gnu.toolchain.cmake会包含mips.toolchain.cmake)里面把-march=mips32r5修改成-march=mips32r2。并且加上ffmpeg的链接路径，并且把-mmsa -mhard-float -O3这些东西删掉。修改后的如下

为什么这么改

增加的-Wl,-rpath-link=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.4.13/install/lib/才是解决 undefined reference to `avcodec_find_encoder@LIBAVCODEC_57那一堆错误的方法，也就是加上ffmpeg库的路径，找到库了就不会报错了。
删掉-mmsa -mhard-float -O3是为了解决后面程序运行时候的illegal instruction，这个illegal instruction的原因一个是硬件上有些计算芯片不支持，另一个就是O3之后有问题，所以这两个删掉。
然后我的君正t41是mips32r2，所以修改成-march=mips32r2

# ----------------------------------------------------------------------------------------------
#  MIPS ToolChanin can be downloaded from https://www.mips.com/develop/tools/codescape-mips-sdk/ .
#  Toolchains with 'mti' in the name (and install directory) are for MIPS R2-R5 instruction sets.
#  Toolchains with 'img' in the name are for MIPS R6 instruction sets.
#  It is recommended to use cmake-gui application for build scripts configuration and generation:
#  1. Run cmake-gui
#  2. Specifiy toolchain file for cross-compiling, mips32r5el-gnu.toolchian.cmake or mips64r6el-gnu.toolchain.cmake
#     can be selected.
#  3. Configure and Generate makefiles.
#  4. make -j4 & make install
# ----------------------------------------------------------------------------------------------

if(COMMAND toolchain_save_config)
  return() # prevent recursive call
endif()

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
if(NOT DEFINED CMAKE_SYSTEM_PROCESSOR)
  set(CMAKE_SYSTEM_PROCESSOR mips)
endif()

include("${CMAKE_CURRENT_LIST_DIR}/gnu.toolchain.cmake")

if(CMAKE_SYSTEM_PROCESSOR STREQUAL mips AND NOT MIPS_IGNORE_FP)
  set(FLOAT_ABI_SUFFIX "")
endif()

if(NOT "x${GCC_COMPILER_VERSION}" STREQUAL "x")
  set(__GCC_VER_SUFFIX "-${GCC_COMPILER_VERSION}")
endif()

if(NOT DEFINED CMAKE_C_COMPILER)
  find_program(CMAKE_C_COMPILER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-gcc${__GCC_VER_SUFFIX})
endif()
if(NOT DEFINED CMAKE_CXX_COMPILER)
  find_program(CMAKE_CXX_COMPILER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-g++${__GCC_VER_SUFFIX})
endif()
if(NOT DEFINED CMAKE_LINKER)
  find_program(CMAKE_LINKER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ld${__GCC_VER_SUFFIX} ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ld)
endif()
if(NOT DEFINED CMAKE_AR)
  find_program(CMAKE_AR NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ar${__GCC_VER_SUFFIX} ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ar)
endif()

if(NOT DEFINED MIPS_LINUX_SYSROOT AND DEFINED GNU_MACHINE)
  set(MIPS_LINUX_SYSROOT /usr/bin)
endif()

if(NOT DEFINED CMAKE_CXX_FLAGS)
  if(CMAKE_SYSTEM_PROCESSOR MATCHES "mips32r5el")
    set(CMAKE_C_FLAGS             "-Wl,-rpath-link=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.4.13/install/lib/ -march=mips32r2 -EL  -mfp64 -mnan=2008 -mabs=2008  -ffp-contract=off " CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-Wl,-rpath-link=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.4.13/install/lib/ -march=mips32r2 -EL  -mfp64 -mnan=2008 -mabs=2008  -ffp-contract=off " CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl -latomic" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "mips64r6el")
    set(CMAKE_C_FLAGS             "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
  endif()
  set(CMAKE_SHARED_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_SHARED_LINKER_FLAGS}")
  set(CMAKE_MODULE_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_MODULE_LINKER_FLAGS}")
  set(CMAKE_EXE_LINKER_FLAGS    "${MIPS_LINKER_FLAGS} ${CMAKE_EXE_LINKER_FLAGS}")
endif()

set(CMAKE_FIND_ROOT_PATH ${CMAKE_FIND_ROOT_PATH} ${MIPS_LINUX_SYSROOT})

set(TOOLCHAIN_CONFIG_VARS ${TOOLCHAIN_CONFIG_VARS}
    MIPS_LINUX_SYSROOT
)
toolchain_save_config()

3.3 配置PKG_CONFIG_LIBDIR

export PKG_CONFIG_LIBDIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-3.4.13/install/lib/pkgconfig/:$PKG_CONFIG_LIBDIR

用PKG_CONFIG_LIBDIR不要用PKG_CONFIG_PATH。

PKG_CONFIG_PATH：用于扩展 pkg-config 的搜索路径，适合添加额外的库路径而不影响默认路径。
PKG_CONFIG_LIBDIR：用于完全替换 pkg-config 的默认搜索路径，适合需要严格控制库路径的场景，如交叉编译。

3.4 cmake

cd build
cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_TOOLCHAIN_FILE=../platforms/linux/mips32r5el-gnu.toolchain.cmake -DCMAKE_INSTALL_PREFIX=../install -DBUILD_TESTS=OFF  -DBUILD_EXAMPLES=OFF -DWITH_FFMPEG=ON -DHAVE_FFMPEG=ON -DBUILD_ZLIB=ON -DZLIB_INCLUDE_DIR=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/3rdparty/zlib ..

cmake命令中也不需要增加那些什么FFMPEG的头文件路径库文件路径一类的。

3.5 编译、安装

make -j
make install

然后

file ../install/lib/libopencv_videoio.so.3.4.9
../install/lib/libopencv_videoio.so.3.4.9: ELF 32-bit LSB shared object, MIPS, MIPS32 rel2 version 1 (SYSV), dynamically linked, with debug_info, not stripped

可以了。

4 软件解码

直接就用opencv的接口读取视频

    VideoCapture cap(inputPath);
    if (!cap.isOpened()) {
        cerr << "Error opening video stream or file" << endl;
        return -1;
    }

4.1 libopencv_core.so: undefined reference to `__atomic_compare_exchange_8'

我的opencv编译通过之后，我把我的opencv库放到我的工程中使用的时候，编译报这个错误

./lib/opencv/libopencv_core.so: undefined reference to `__atomic_compare_exchange_8'
./lib/opencv/libopencv_core.so: undefined reference to `__atomic_fetch_sub_8'
./lib/opencv/libopencv_core.so: undefined reference to `__atomic_load_8'
./lib/opencv/libopencv_core.so: undefined reference to `__atomic_store_8'
./lib/opencv/libopencv_core.so: undefined reference to `__atomic_fetch_add_8'
collect2: error: ld returned 1 exit status

我本来以为又是opencv编译有问题，但是我去看了下我opencv的opencv-3.4.9/platforms/linux/mips.toolchain.cmake里面有一个

set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl -latomic" CACHE INTERNAL "Added for mips cross build error")

然后那么我又看了下我的工程的makefile，我觉得问题在于我工程中没有包含atomic，所以我在工程的makefile中增加-latomic，重新编译，问题解决。

4.2 illegal instruction

再次运行程序，提示illegal instruction，然后网上搜大多数说是ffmpeg的问题，但是我按照网上的各种方法试了，不行，然后我调试发现

那就是跟opencv有关系，于是我修改opencv-3.4.9/platforms/linux/mips.toolchain.cmake把里面的类似-mmsa -mhard-float -O3等这些东西去掉，最终改成

# ----------------------------------------------------------------------------------------------
#  MIPS ToolChanin can be downloaded from https://www.mips.com/develop/tools/codescape-mips-sdk/ .
#  Toolchains with 'mti' in the name (and install directory) are for MIPS R2-R5 instruction sets.
#  Toolchains with 'img' in the name are for MIPS R6 instruction sets.
#  It is recommended to use cmake-gui application for build scripts configuration and generation:
#  1. Run cmake-gui
#  2. Specifiy toolchain file for cross-compiling, mips32r5el-gnu.toolchian.cmake or mips64r6el-gnu.toolchain.cmake
#     can be selected.
#  3. Configure and Generate makefiles.
#  4. make -j4 & make install
# ----------------------------------------------------------------------------------------------

if(COMMAND toolchain_save_config)
  return() # prevent recursive call
endif()

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
if(NOT DEFINED CMAKE_SYSTEM_PROCESSOR)
  set(CMAKE_SYSTEM_PROCESSOR mips)
endif()

include("${CMAKE_CURRENT_LIST_DIR}/gnu.toolchain.cmake")

if(CMAKE_SYSTEM_PROCESSOR STREQUAL mips AND NOT MIPS_IGNORE_FP)
  set(FLOAT_ABI_SUFFIX "")
endif()

if(NOT "x${GCC_COMPILER_VERSION}" STREQUAL "x")
  set(__GCC_VER_SUFFIX "-${GCC_COMPILER_VERSION}")
endif()

if(NOT DEFINED CMAKE_C_COMPILER)
  find_program(CMAKE_C_COMPILER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-gcc${__GCC_VER_SUFFIX})
endif()
if(NOT DEFINED CMAKE_CXX_COMPILER)
  find_program(CMAKE_CXX_COMPILER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-g++${__GCC_VER_SUFFIX})
endif()
if(NOT DEFINED CMAKE_LINKER)
  find_program(CMAKE_LINKER NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ld${__GCC_VER_SUFFIX} ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ld)
endif()
if(NOT DEFINED CMAKE_AR)
  find_program(CMAKE_AR NAMES ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ar${__GCC_VER_SUFFIX} ${GNU_MACHINE}${FLOAT_ABI_SUFFIX}-ar)
endif()

if(NOT DEFINED MIPS_LINUX_SYSROOT AND DEFINED GNU_MACHINE)
  set(MIPS_LINUX_SYSROOT /usr/bin)
endif()

if(NOT DEFINED CMAKE_CXX_FLAGS)
  if(CMAKE_SYSTEM_PROCESSOR MATCHES "mips32r5el")
    set(CMAKE_C_FLAGS             "-Wl,-rpath-link=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-4.1.3/install/lib/ -march=mips32r2 -EL -mmsa -mhard-float -mfp64 -mnan=2008 -mabs=2008 -O3 -ffp-contract=off -mtune=p5600" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-Wl,-rpath-link=/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/ffmpeg-4.1.3/install/lib/ -march=mips32r2 -EL -mmsa -mhard-float -mfp64 -mnan=2008 -mabs=2008 -O3 -ffp-contract=off -mtune=p5600" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl -latomic" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections  -Wa,--noexecstack -fsigned-char -Wno-psabi")
  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "mips64r6el")
    set(CMAKE_C_FLAGS             "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_SHARED_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_CXX_FLAGS           "-O3 -march=i6500 -EL -mmsa -mabi=64 -mhard-float -mfp64 -mnan=2008" CACHE INTERNAL "")
    set(CMAKE_MODULE_LINKER_FLAGS "" CACHE INTERNAL "")
    set(CMAKE_EXE_LINKER_FLAGS    "-lpthread -lrt -ldl" CACHE INTERNAL "Added for mips cross build error")

    set(CMAKE_CXX_FLAGS           "${CMAKE_CXX_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
    set(CMAKE_C_FLAGS             "${CMAKE_C_FLAGS} -fdata-sections -Wa,--noexecstack -fsigned-char -Wno-psabi")
  endif()
  set(CMAKE_SHARED_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_SHARED_LINKER_FLAGS}")
  set(CMAKE_MODULE_LINKER_FLAGS "${MIPS_LINKER_FLAGS} ${CMAKE_MODULE_LINKER_FLAGS}")
  set(CMAKE_EXE_LINKER_FLAGS    "${MIPS_LINKER_FLAGS} ${CMAKE_EXE_LINKER_FLAGS}")
endif()

set(CMAKE_FIND_ROOT_PATH ${CMAKE_FIND_ROOT_PATH} ${MIPS_LINUX_SYSROOT})

set(TOOLCHAIN_CONFIG_VARS ${TOOLCHAIN_CONFIG_VARS}
    MIPS_LINUX_SYSROOT
)
toolchain_save_config()

然后不报错illegal instruction了，但是运行又出现了新的错误。

4.3 错误： CAP_IMAGES: Stop scanning. Can't read image file

 ./gdbserver :1234 ./sku_demo  ./image/test.h264   ./image/masaic.mp4
Process ./sku_demo created; pid = 696
Listening on port 1234
Remote debugging from host 192.168.1.10
[AIP@12b00000] successfully initialized, version[10105]
inputPath: ./image/test.h264
[ INFO:0] VIDEOIO: Enabled backends(4, sorted by priority): FFMPEG(1000); V4L2(990); CV_IMAGES(980); CV_MJPEG(970)
warning: Error opening file (/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/modules/videoio/src/cap_ffmpeg_impl.hpp:940)
warning: ./image/test.h264 (/data3/sku_mount/chw/x264_ffmpeg_opencv_20241230/opencv-3.4.9/modules/videoio/src/cap_ffmpeg_impl.hpp:941)
[ INFO:0] Pattern: ./image/test.h%03d @ 264
[ INFO:0] CAP_IMAGES: Stop scanning. Can't read image file: ./image/test.h264
Error opening video stream or file

Child exited with status 255

我明明是想打开视频，但是报错怎么是image file，论七八糟的，我现在先不运行我的工程代码了，我先试试命令行不行，先保证命令行了之后再往下进行。

./ffmpeg -i /mnt/chw/cars.mp4 -threads 0 -f mp4 -movflags +faststart decoded_output.mp4

我又重新下载ffmpeg代码，然后编译完了之后，./ffmpeg -i /mnt/chw/cars.mp4 -threads 0 -f mp4 -movflags +faststart decoded_output.mp4
可以用了，但是继续运行我的工程代码，发现还是报错

 ./sku_demo ./image/cars.mp4 ./image/m
as.mp4
[AIP@12b00000] successfully initialized, version[10105]
inputPath: ./image/cars.mp4
[ INFO:0] VIDEOIO: Enabled backends(4, sorted by priority): FFMPEG(1000); V4L2(990); CV_IMAGES(980); CV_MJPEG(970)
OpenCV: FFMPEG: tag 0x34363248/'H264' is not supported with codec id 28 and format 'mp4 / MP4 (MPEG-4 Part 14)'
OpenCV: FFMPEG: fallback to use tag 0x31637661/'avc1'
[h264_v4l2m2m @ 0xa84560] Could not find a valid device
[h264_v4l2m2m @ 0xa84560] can't configure encoder
Could not open codec 'h264_v4l2m2m': Unspecified error
Could not open the output video file for write

这是因为我不仅仅用ffmpeg解码，我还用他编码了，我先把编码的删掉，只用opencv ffmpeg打开视频就不会报错了，至于编码后面我会用君正的SDK做硬件编码。

5 交叉编译ffmepg----正确步骤，直接看这个

通过上面的这些错误，我重新整理了一下正确的步骤。

5.1 下载源码

Download FFmpeg

这次下载3.4.13的版本。

5.2 配置

tar xzvf ffmpeg-3.4.13.tar.gz 
cd ffmpeg-3.4.13/
mkdir install

 ./configure --cross-prefix=mips-linux-uclibc- --enable-cross-compile --target-os=linux --cc=mips-linux-uclibc-gcc --arch=mips --prefix=$PWD/install --enable-shared --disable-static --enable-ffmpeg --enable-mips32r2 --disable-mips32r5 --disable-mips64r2 --disable-mips32r6 --disable-mips64r6 --disable-mipsdsp --disable-mipsdspr2 --disable-mipsfpu

5.3 编译、安装

make -j
make install

然后在板子上用下面的命令发现可以

./ffmpeg -i /mnt/chw/cars.mp4 -threads 0 -f mp4 -movflags +faststart decoded_output.mp4

参考文献：

Linux aarch64-linux-gnu-交叉编译x264、ffmpeg、opencv并移植-CSDN博客

ubuntu交叉编译opencv-CSDN博客

RK1808交叉编译opencv with ffmpeg（解决FFMPEG始终为NO）_交叉编译opencv带有ffmpeg-CSDN博客

OpenCV+FFmpeg交叉编译_opencv ffmpeg-CSDN博客

Linux aarch64-linux-gnu-交叉编译x264、ffmpeg、opencv并移植-CSDN博客

Download FFmpeg