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• How to find the presentation time stamp of a given frame number for FFMPEG decoding ?

  21 août 2017, par Deepankar Arya

  I am using the C APIs of ffmpeg for some video processing. My aim is to extract the screen shot of a given frame number. I have understood that ffmpeg has an av_seek_frame function to seek to a given timestamp(expressed in appropriated base units of the video stream). I assume that I will have to goto to the most recent I frame for the given frame(using the AVSEEK_FLAG_BACKWARD flag) and read onwards untill I meet the required frame. For that I need to give a seek time stamp to the av_seek_frame function. My main issue is that given a frame number, how do I find an associated presentation time stamp to seek to ?

• comple librtmp for android error : cannot find -ldl collect2 : error : ld returned 1 exit status

  26 mars 2014, par hosein

  I have problem on comple librtmp for android using :
  https://github.com/OnlyInAmerica/FFmpeg-Android

  ./build_librtmp_for_android.sh

  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot open crtbegin_so.o: No such file or directory
  
  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot open crtend_so.o: No such file or directory
  
  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot find -lssl
  
  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot find -lcrypto
  
  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot find -lz
  
  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot find -lc
  
  /home/user/loc_app/android-ndk-r9d/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld: error: cannot find -ldl
  
  collect2: error: ld returned 1 exit status
  
  make: *** [librtmp.so.1] Error 1

  here is build_librtmp_for_android.sh :

  #!/bin/bash
  
  NDK=/home/user/loc_app/android-ndk-r9
  
  #/home/user/loc_app/android-ndk-r9/platforms/android-19/arch-arm
  
  SYSROOT=$NDK/platforms/android-18/arch-arm
  
  #platforms/android-19/arch-arm/
  
  TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64
  
  #/home/user/loc_app/android-ndk-r9/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64
  
  OPENSSL_DIR=/home/user/libs/openssl-android-master/
  
  # Note: Change the above variables for your system.
  
  function build_one
  
  {
  
      set -e
  
      make clean
  
      ln -s ${SYSROOT}usr/lib/crtbegin_so.o
  
      ln -s ${SYSROOT}usr/lib/crtend_so.o
  
      export XLDFLAGS="$ADDI_LDFLAGS -L${OPENSSL_DIR}libs/armeabi -L${SYSROOT}usr/lib "
  
      export CROSS_COMPILE=$TOOLCHAIN/bin/arm-linux-androideabi-
  
      export XCFLAGS="${ADDI_CFLAGS} -I${OPENSSL_DIR}include -isysroot ${SYSROOT}"
  
      export INC="-I${SYSROOT}"
  
      make prefix=\"${PREFIX}\" OPT= install 
  
  }
  
  CPU=arm
  
  PREFIX=$(pwd)/android/$CPU 
  
  ADDI_CFLAGS="-marm"
  
  build_one

  OS : Fedora 64bit

  EDIT 1 : that seems to Makefile so i added it here

  VERSION=v2.4
  
  
  
  prefix=/usr/local
  
  
  
  incdir=$(prefix)/include/librtmp
  
  bindir=$(prefix)/bin
  
  libdir=$(prefix)/lib
  
  mandir=$(prefix)/man
  
  BINDIR=$(DESTDIR)$(bindir)
  
  INCDIR=$(DESTDIR)$(incdir)
  
  LIBDIR=$(DESTDIR)$(libdir)
  
  MANDIR=$(DESTDIR)$(mandir)
  
  
  
  CC=$(CROSS_COMPILE)gcc
  
  LD=$(CROSS_COMPILE)ld
  
  AR=$(CROSS_COMPILE)ar
  
  
  
  SYS=posix
  
  CRYPTO=OPENSSL
  
  #CRYPTO=GNUTLS
  
  DEF_POLARSSL=-DUSE_POLARSSL
  
  DEF_OPENSSL=-DUSE_OPENSSL
  
  DEF_GNUTLS=-DUSE_GNUTLS
  
  DEF_=-DNO_CRYPTO
  
  REQ_GNUTLS=gnutls,hogweed,nettle
  
  REQ_OPENSSL=libssl,libcrypto
  
  PUB_GNUTLS=-lgmp
  
  LIBZ=-lz
  
  LIBS_posix=
  
  LIBS_darwin=
  
  LIBS_mingw=-lws2_32 -lwinmm -lgdi32
  
  LIB_GNUTLS=-lgnutls -lhogweed -lnettle -lgmp $(LIBZ) 
  
  LIB_OPENSSL=-lssl -lcrypto $(LIBZ)
  
  LIB_POLARSSL=-lpolarssl $(LIBZ)
  
  PRIVATE_LIBS=$(LIBS_$(SYS))
  
  CRYPTO_LIB=$(LIB_$(CRYPTO)) $(PRIVATE_LIBS)
  
  CRYPTO_REQ=$(REQ_$(CRYPTO))
  
  CRYPTO_DEF=$(DEF_$(CRYPTO))
  
  PUBLIC_LIBS=$(PUB_$(CRYPTO))
  
  
  
  SO_VERSION=1
  
  SOX_posix=so
  
  SOX_darwin=dylib
  
  SOX_mingw=dll
  
  SOX=$(SOX_$(SYS))
  
  SO_posix=.$(SOX).$(SO_VERSION)
  
  SO_darwin=.$(SO_VERSION).$(SOX)
  
  SO_mingw=-$(SO_VERSION).$(SOX)
  
  SO_EXT=$(SO_$(SYS))
  
  
  
  SODIR_posix=$(LIBDIR)
  
  SODIR_darwin=$(LIBDIR)
  
  SODIR_mingw=$(BINDIR)
  
  SODIR=$(SODIR_$(SYS))
  
  
  
  SO_LDFLAGS_posix=-shared -Wl,-soname,$@
  
  SO_LDFLAGS_darwin=-dynamiclib -twolevel_namespace -undefined dynamic_lookup \
  
      -fno-common -headerpad_max_install_names -install_name $(libdir)/$@
  
  SO_LDFLAGS_mingw=-shared -Wl,--out-implib,librtmp.dll.a
  
  SO_LDFLAGS=$(SO_LDFLAGS_$(SYS))
  
  
  
  INSTALL_IMPLIB_posix=
  
  INSTALL_IMPLIB_darwin=
  
  INSTALL_IMPLIB_mingw=cp librtmp.dll.a $(LIBDIR)
  
  INSTALL_IMPLIB=$(INSTALL_IMPLIB_$(SYS))
  
  
  
  SHARED=yes
  
  SODEF_yes=-fPIC
  
  SOLIB_yes=librtmp$(SO_EXT)
  
  SOINST_yes=install_so
  
  SO_DEF=$(SODEF_$(SHARED))
  
  SO_LIB=$(SOLIB_$(SHARED))
  
  SO_INST=$(SOINST_$(SHARED))
  
  
  
  DEF=-DRTMPDUMP_VERSION=\"$(VERSION)\" $(CRYPTO_DEF) $(XDEF)
  
  OPT=-O2
  
  CFLAGS=-Wall $(XCFLAGS) $(INC) $(DEF) $(OPT) $(SO_DEF) 
  
  LDFLAGS=$(XLDFLAGS)
  
  
  
  
  
  OBJS=rtmp.o log.o amf.o hashswf.o parseurl.o
  
  
  
  all:    librtmp.a $(SO_LIB)
  
  
  
  clean:
  
      rm -f *.o *.a *.$(SOX) *$(SO_EXT) librtmp.pc
  
  
  
  librtmp.a: $(OBJS)
  
      $(AR) rs $@ $?
  
  
  
  librtmp$(SO_EXT): $(OBJS)
  
      $(CC) $(SO_LDFLAGS) $(LDFLAGS) -o $@ $^ $> $(CRYPTO_LIB)
  
      ln -sf $@ librtmp.$(SOX)
  
  
  
  log.o: log.c log.h Makefile
  
  rtmp.o: rtmp.c rtmp.h rtmp_sys.h handshake.h dh.h log.h amf.h Makefile
  
  amf.o: amf.c amf.h bytes.h log.h Makefile
  
  hashswf.o: hashswf.c http.h rtmp.h rtmp_sys.h Makefile
  
  parseurl.o: parseurl.c rtmp.h rtmp_sys.h log.h Makefile
  
  
  
  librtmp.pc: librtmp.pc.in Makefile
  
      sed -e "s;@prefix@;$(prefix);" -e "s;@libdir@;$(libdir);" \
  
          -e "s;@VERSION@;$(VERSION);" \
  
          -e "s;@CRYPTO_REQ@;$(CRYPTO_REQ);" \
  
          -e "s;@PUBLIC_LIBS@;$(PUBLIC_LIBS);" \
  
          -e "s;@PRIVATE_LIBS@;$(PRIVATE_LIBS);" librtmp.pc.in > $@
  
  
  
  install:    install_base $(SO_INST)
  
  
  
  install_base:   librtmp.a librtmp.pc
  
      -mkdir -p $(INCDIR) $(LIBDIR)/pkgconfig $(MANDIR)/man3 $(SODIR)
  
      cp amf.h http.h log.h rtmp.h $(INCDIR)
  
      cp librtmp.a $(LIBDIR)
  
      cp librtmp.pc $(LIBDIR)/pkgconfig
  
      cp librtmp.3 $(MANDIR)/man3
  
  
  
  install_so: librtmp$(SO_EXT)
  
      cp librtmp$(SO_EXT) $(SODIR)
  
      $(INSTALL_IMPLIB)
  
      cd $(SODIR); ln -sf librtmp$(SO_EXT) librtmp.$(SOX)

• Can't find ffmpeg.exe [on hold]

  31 juillet 2017, par Eldar Azulay

  I want to use ffmpeg for my c# program, so I downloaded it from their website here : https://www.ffmpeg.org/download.html by clicking on the big green button, but in this archive there’s no exe, which I need to run so I can use it.
  This is that I see when opening the file I downloaded :
  

  I just want to know how can I get the ffmpeg.exe file.