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• Undefined reference to av_log

  12 novembre 2017, par Dana Prakoso

  I am cross-compiling FFMPEG source in Linux for Windows using i686-w64-mingw32 using this script :

  ../ffmpeg/configure --disable-ffmpeg --disable-ffprobe --disable-ffplay --disable-shared --enable-static --arch=x86 --target-os=mingw32 --cross-prefix=i686-w64-mingw32- --enable-cross-compile

  And it generates all static library files with extension *.a inside "lib" folder. Then I try to link those libraries with my own source, with this script :

  i686-w64-mingw32-gcc -m32 -c videoplayer.c -o videoplayer.o -w $(INCLUDEDIR) -Wl,--add-stdcall-alias
  
  i686-w64-mingw32-gcc -static -m32 -o libvideoplayer.dll videoplayer.o -Wl,--out-implib,libvideoplayer_dll.lib -Wl,--add-stdcall-alias -L../../ffmpeg/lib -lavdevice -lavformat -lavcodec -lavutil -lwsock32 -lswresample ../../ffmpeg/lib/libWs2_32.lib

  And I got this bunch of error messages :

  ../../ffmpeg/lib/libavformat.a(rtpproto.o): In function `rtp_resolve_host':
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/rtpproto.c:140: undefined reference to `_imp__getaddrinfo@16'
  
  ../../ffmpeg/lib/libavformat.a(rtpproto.o): In function `rtp_parse_addr_list':
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/rtpproto.c:282: undefined reference to `_imp__freeaddrinfo@4'
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/rtpproto.c:277: undefined reference to `_imp__freeaddrinfo@4'
  
  ../../ffmpeg/lib/libavformat.a(tcp.o): In function `tcp_open':
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/tcp.c:112: undefined reference to `_imp__getaddrinfo@16'
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/tcp.c:114: undefined reference to `_imp__getaddrinfo@16'
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/tcp.c:177: undefined reference to `_imp__freeaddrinfo@4'
  
  /home/dana/Sources/build-ffmpeg/src/libavformat/tcp.c:192: undefined reference to `_imp__freeaddrinfo@4'

  How do I resolve this ? Do I miss something in my script ? Big thanks for someone replying.

• Building ffmpeg for ARM with libopencore-amr support

  20 janvier 2013, par brux

  I am trying to build ffmpeg with opencore-amr and libx264 support, I found this build script http://sourceforge.net/projects/ffmpeg4android/, this compiles as expected, the resultant binary works fine on the device and —enable-libx264 appears in the output of the binary when I pass no arguments.

  However when I try to include support for libopencore-amr it doesnt seem to work, I have installed libopencore-amr and libopencore-amr-devel (I should add that I have tried this whole procedure on both fedora and ubuntu). I modified the Android_Configure.mk file so that it looks like this :

  FF_CONFIGURATION_STRING := \
  
      --arch=$(TARGET_ARCH) \
  
      --target-os=linux \
  
      --enable-cross-compile \
  
      --cross-prefix=$(NDK_CROSS_
  
  PREFIX) \
  
      --sysroot=$(NDK_SYSROOT) \
  
      --enable-shared \
  
      --enable-static \
  
      --enable-libopencore-amrnb   <-- i've added this line

  However when I run ./configure I see :

  libopencore-amrnb support no
  
  libopencore-amrwb support no

  Despite this the build goes well with zero compilation errors. When I run ffmpeg on the device everything seems to work however there is definitely no support for amrnb.

• using ffmpeg to automate splitting video into quarters and stacking

  11 février 2014, par user3297049

  I need to create a quick FFMPEG batch file that takes a very wide video file and splits it into quaters (dimension wise not time wise), then outputting a file where each quarter is under the previous.

  E.g.

  A B C D

  would become
  A
  B
  C
  D
  

  I know this should be possible with crop and pad commands, and through research I've found that someone divided into quarters and put the top left and bottom right next to each other horizontally using :

  "% dp0\ffmpeg.exe" -i %1 -filter_complex "[0:0]crop=iw/2:ih/2:0:0,pad=iw*2:ih:0:0[tl] ;[0:0]crop=iw/2:ih:iw/2:ih/2[br] ;[tl][br]overlay=W/2" -b:v 32000k -b:a 128k %1_2.avi

  Can anyone help as the command line is beyond me.
  Thanks
  Steve