“Undefined Reference” when compiling FFMPEG with librtmp on Android

问题

I have searched, and while Building FFMPEG with librtmp for android answered part of my question, I ran into other issues further along in the compilation process.

First, I am trying to use the script in this github repo, changing the flags to include

  --enable-librtmp \
  --extra-cflags=-I/home/bradford/Development/FFMPEG/rtmp/rtmpdump/librtmp/ \
  --extra-ldflags=-L/home/bradford/Development/FFMPEG/rtmp/rtmpdump/librtmp"

I build librtmp with polarSSL following S74ck3r's instructions on his github repo and stream-recorder thread. That appears to work correctly, and I have a librtmp.so, librtmp.a and rtmp.h

When I try to compile ffmpeg with librtmp, I get the error

ERROR: librtmp not found

This SO question helped, and I modified ffmpeg's config file so that it wouldn't look at pkg-config for librtmp (even though pkg-config was aware of librtmp...):

#enabled librtmp    && require_pkg_config librtmp librtmp/rtmp.h RTMP_Socket

When I build now, it starts successfully, and I get the hopeful line:

librtmp enabled           yes

And later on I see more good news:

...
Enabled protocols:
applehttp       http            mmsh
cache           httpproxy       mmst
concat          librtmp         mmsu
crypto          librtmpe        pipe
fd          librtmps        rtp
file            librtmpt        tcp
gopher          librtmpte       udp
hls         md5
...

but finally, after compiling everything and during the installation phase, I get these types of errors:

INSTALL   libavutil/libavutil.pc
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_get_file_handle:libavformat/librtmp.c:190: error: undefined reference to 'RTMP_Socket'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_read_seek:libavformat/librtmp.c:180: error: undefined reference to 'RTMP_SendSeek'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_read_pause:libavformat/librtmp.c:161: error: undefined reference to 'RTMP_Pause'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_close:libavformat/librtmp.c:64: error: undefined reference to 'RTMP_Close'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_write:libavformat/librtmp.c:145: error: undefined reference to 'RTMP_Write'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_read:libavformat/librtmp.c:153: error: undefined reference to 'RTMP_Read'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:96: error: undefined reference to 'RTMP_LogSetLevel'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:97: error: undefined reference to 'RTMP_LogSetCallback'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:118: error: undefined reference to 'RTMP_Init'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:119: error: undefined reference to 'RTMP_SetupURL'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:127: error: undefined reference to 'RTMP_Connect'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:127: error: undefined reference to 'RTMP_ConnectStream'
/tmp/FFMPEG/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: libavformat/librtmp.o: in function rtmp_open:libavformat/librtmp.c:125: error: undefined reference to 'RTMP_EnableWrite'
collect2: ld returned 1 exit status

And I can't get past them. It sounds like it can't find rtmp.h, which includes references to those functions, but that is present where it should be (afaik).

Also, my project requires librtmp - the built-in rtmp features of ffmpeg are not sufficient because I require the authentication features of librtmp.

回答1:

Thanks for breaking this out into a separate question and thoroughly spelling out your process and problem.

Based on the provided data, you were able to build FFmpeg and execute the binary in order to see the list of protocols. But the installation phase failed? The rtmp.h file must have been present because the binary build (.h is needed during compilation-time, not link-time or run-time).

My best guess is that your compiled FFmpeg binary is dynamically linked to librtmp.so. Did you copy librtmp.so onto this system (assuming cross-compilation here)? If it's present, did you run /sbin/ldconfig in order to register the library? Run ldd ffmpeg to see what .so libraries the FFmpeg binrary wants to see. Is it missing a link to librtmp.so?

回答2:

I've documented my process of successfully building FFmpeg 2.1.3 with librtmp for Android.

Briefly, once you build Open/PolarSSL and librtmp, download the latest FFmpeg release and make the following changes to FFmpeg's configure:

# ffmpegX.X.X/configure
...
# Replace the following lines:

#SLIBNAME_WITH_MAJOR='$(SLIBNAME).$(LIBMAJOR)'
#LIB_INSTALL_EXTRA_CMD='$$(RANLIB) "$(LIBDIR)/$(LIBNAME)"'
#SLIB_INSTALL_NAME='$(SLIBNAME_WITH_VERSION)'
#SLIB_INSTALL_LINKS='$(SLIBNAME_WITH_MAJOR) $(SLIBNAME)'

# With: 

SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'
LIB_INSTALL_EXTRA_CMD='$$(RANLIB) "$(LIBDIR)/$(LIBNAME)"'
SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)'
SLIB_INSTALL_LINKS='$(SLIBNAME)'

...

# Replace this:
#enabled librtmp    && require_pkg_config librtmp librtmp/rtmp.h RTMP_Socket
# With:
enabled librtmp    && require librtmp librtmp/rtmp.h RTMP_Socket -L/path/to/rtmpdump/librtmp/android/arm/lib -lrtmp

Then use the following build script to compile FFmpeg:

# ffmpegX.X.X/build_ffmpeg_with_librtmp_for_android.sh
#!/bin/bash
NDK=/path/to/android-ndk-r9c
SYSROOT=$NDK/platforms/android-19/arch-arm/
TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/darwin-x86_64

OPENSSL_DIR=/path/to/openssl-android/
LIBRTMP_DIR=/path/to/rtmpdump/librtmp/
# Note: Change above variables to match your system
function build_one
{
./configure \
    --prefix=$PREFIX \
    --enable-librtmp \
    --enable-shared \
    --disable-static \
    --disable-doc \
    --disable-programs \
    --disable-doc \
    --disable-symver \
    --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
    --target-os=linux \
    --arch=arm \
    --enable-cross-compile \
    --sysroot=$SYSROOT \
    --extra-cflags="-Os -fpic $ADDI_CFLAGS" \
    --extra-ldflags="$ADDI_LDFLAGS" \
    $ADDITIONAL_CONFIGURE_FLAG
make clean
make -j8
make install
}
CPU=arm
PREFIX=$(pwd)/android/$CPU 
ADDI_CFLAGS="-marm -I${OPENSSL_DIR}include -I${LIBRTMP_DIR}android/arm/include -L${LIBRTMP_DIR}android/arm/lib -lrtmp"
ADDI_LFLAGS="-L${OPENSSL_DIR}libs/armeabi -L${LIBRTMP_DIR}android/arm/lib -lrtmp" 
build_one

Incredible thanks to my pal Chris for helping me through this.

回答3:

I guess you didn't link the library rtmp in your project. you need to link the rtmp library like this

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -L${CMAKE_SOURCE_DIR}/src/main/cpp/libs/${CMAKE_ANDROID_ARCH_ABI}")

target_link_libraries( native-lib avformat avcodec avfilter avutil swresample swscale z rtmp)

来源：https://stackoverflow.com/questions/20721445/undefined-reference-when-compiling-ffmpeg-with-librtmp-on-android

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