Cannot compile, using ffmpeg from sources

[xultz]

Hello, I'm using Ubuntu 18.04, did a clean install in a virtual machine. I downloaded libvpx from sources, compiled and installed without any problems. Then I downloaded ffmpeg source (from git, from git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg), and compiled it (passing --enable-libvpx to it), make compiled without any issues, and did a make install.

When I try to make the 0_hello_world.c, make gives me the following error: (you can check the output with a better looking text at https://pastebin.com/wPKY99ue )

mkdir build gcc -g -Wall -o build/hello_world -lavformat -lavcodec -lswscale -lavutil -lz 0_hello_world.c
&& ./build/hello_world small_bunny_1080p_60fps.mp4` 0_hello_world.c: In function ‘main’: 0_hello_world.c:35:3: warning: ‘av_register_all’ is deprecated [-Wdeprecated-declarations] av_register_all(); ^~~~~~~~~~~~~~~ In file included from 0_hello_world.c:15:0: /usr/local/include/libavformat/avformat.h:2033:6: note: declared here void av_register_all(void); ^~~~~~~~~~~~~~~ /tmp/ccbsfyh8.o: In function 'av_make_error_string': /usr/local/include/libavutil/error.h:111: undefined reference to 'av_strerror' /tmp/ccbsfyh8.o: In function 'main': /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:35: undefined reference to 'av_register_all' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:40: undefined reference to 'avformat_alloc_context' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:54: undefined reference to 'avformat_open_input' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:73: undefined reference to 'avformat_find_stream_info' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:103: undefined reference to 'avcodec_find_decoder' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:125: undefined reference to 'avcodec_alloc_context3' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:134: undefined reference to 'avcodec_parameters_to_context' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:142: undefined reference to 'avcodec_open2' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:149: undefined reference to 'av_frame_alloc' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:156: undefined reference to 'av_packet_alloc' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:180: undefined reference to 'av_packet_unref' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:168: undefined reference to 'av_read_frame' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:185: undefined reference to 'avformat_close_input' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:186: undefined reference to 'avformat_free_context' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:187: undefined reference to 'av_packet_free' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:188: undefined reference to 'av_frame_free' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:189: undefined reference to 'avcodec_free_context' /tmp/ccbsfyh8.o: In function 'decode_packet': /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:207: undefined reference to 'avcodec_send_packet' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:218: undefined reference to 'avcodec_receive_frame' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:230: undefined reference to 'av_get_picture_type_char' /home/xultz/libav/ffmpeg-libav-tutorial/0_hello_world.c:242: undefined reference to 'av_frame_unref' collect2: error: ld returned 1 exit status Makefile:4: recipe for target 'hello_world' failed make: *** [hello_world] Error 1

I took a look at pkg-config outputs from --libs and --cflags for some libs (lib libavformat, libavutil, etc) and I changed the gcc line on the Makefile to the following, but I couldn't see any changes on the make output: gcc -g -Wall -I/usr/local/include -o build/hello_world -L/usr/local/lib -lavformat -lavcodec -lswscale -lavutil -lz -lvpx -lm -lswresample -pthread 0_hello_world.c

What else can I do in order to compile the code?

Thank you in advance for any help!

[ginaluca]

Hi,

I'm compiling with a different setup (on Ubuntu16 and not from ffmpeg sources) but I had a similar error, so my solution might work for you as well.

I moved all the library parameters after the source file name, like this: gcc -g -Wall -o build/hello_world 0_hello_world.c -lavformat -lavcodec -lswscale -lavutil -lz

and I could compile successfully.

[hustzhao]

Hi I use Ubuntu18.04, and ffmpeg-4.0.1 source code, and use ./configure --disable-x86asm --disable-doc --prefix=output to make, make install

I use gcc -o build/hello_world -g -Wall 0_hello_world.c -I./include -L./lib -lavformat -lavcodec -lswscale -lavutil -lswresample -lz -lm -lpthread It could compile well

[hxtruong6]

I have same errors. How to build with CMakeLists.txt in Clion IDE of intellij? I add -lavformat -lavcodec -lswscale -lavutil -lz to target_link_libraries but the output like /usr/bin/ld: cannot find -lavformat_alloc_context.

[hxtruong6]

I have same errors. How to build with CMakeLists.txt in Clion IDE of intellij? I add -lavformat -lavcodec -lswscale -lavutil -lz to target_link_libraries but the output like /usr/bin/ld: cannot find -lavformat_alloc_context.

I solved: target_link_libraries(avformat avutil). Adding other if necessary. I think with lavformat, I can drop l characer.

[vandanachadha]

For me, the following worked: gcc -g -Wall -L/home/vandana/ffmpeg/ /home/vandana/ipdecoder/ffmpeg_custom/transcoding.c /home/vandana/ipdecoder/ffmpeg_custom/video_debugging.c -lavformat -lavcodec -lx264 -lavdevice -lavfilter -lavutil -lswscale -lswresample -lm -lz -lpthread -o /home/vandana/ipdecoder/ffmpeg_custom/build/transcoding

[Canta]

Instructions for Ubuntu 20.04, using ffmpeg from master branch on git repo (as of 2021-02-28). Asuming a "ffmpeg" directory created inside home.

1. ffmpeg repo:
   • cd ~/ffmpeg
   • git clone https://git.ffmpeg.org/ffmpeg.git repo
   • cd repo
   • ./configure --enable-gpl --disable-programs (this may vary, but the point of "disable programs" is to not replace the ffmpeg executable from ubuntu repos: we just need the libs for this tutorial).
   • make
   • sudo make install
2. ffmpeg-libav-tutorial "hello world" compilation:
   • cd ~/ffmpeg
   • git clone https://github.com/leandromoreira/ffmpeg-libav-tutorial
   • cd ffmpeg-libav-tutorial
   • gcc -g -Wall 0_hello_world.c $(pkg-config --libs libavformat libavcodec libavdevice libavfilter libavutil libswscale libswresample) -lz -o build/hello