Cannot connect mpg123 and ao in project with cmakelists - c++

Question

I am using the cmakelists.txt below, that exists in the top folder of my project, and I am trying to connect mpg123 and ao to my project. In one .cpp file of the source folder I added a code with mpg123 and ao to play a song. This code can be compiled with this line:
g++ mpg.cpp -lmpg123 -lao -o mpg
I also added this line:
target_link_libraries(emotime ${LIBAO_LIBRARIES} ${MPG123_LIBRARIES})
in the cmakelists that exists in my source folder. When I am running make I get errors like "undefined reference to ao_initialize'" and "undefined reference tompg123_init'" in this piece of code:
int playaudio(int trackid)
{
char * traklink="";
int tid=trackid;
if (tid==1){
traklink= "/home/mixa/tutti_frutti.wav";
}
else if (tid==2){
traklink= "/home/mixa/karavi.wav";
}
else if (tid==3){
traklink= "/home/mixa/timon.wav";
}
else if (tid==4){
traklink= "/home/mixa/hippo.wav";
}
else{
traklink= "/home/mixa/nanourisma.wav";
}
mpg123_handle *mh;
unsigned char *buffer;
size_t buffer_size;
size_t done;
int err;
int driver;
ao_device *dev;
ao_sample_format format;
int channels, encoding;
long rate;
/* if(argc < 2)
exit(0);
*/
/* initializations */
ao_initialize();
driver = ao_default_driver_id();
mpg123_init();
mh = mpg123_new(NULL, &err);
buffer_size = mpg123_outblock(mh);
buffer = (unsigned char*) malloc(buffer_size * sizeof(unsigned char));
/* open the file and get the decoding format */
//mpg123_open(mh,traklink);
mpg123_open(mh,traklink);
mpg123_getformat(mh, &rate, &channels, &encoding);
/* set the output format and open the output device */
format.bits = mpg123_encsize(encoding) * BITS;
format.rate = rate;
format.channels = channels;
format.byte_format = AO_FMT_NATIVE;
format.matrix = 0;
dev = ao_open_live(driver, &format, NULL);
/* decode and play */
while (mpg123_read(mh, buffer, buffer_size, &done) == MPG123_OK)
//ao_play(dev, buffer, done);
ao_play(dev, (char*)buffer, done);
/* clean up */
free(buffer);
ao_close(dev);
mpg123_close(mh);
mpg123_delete(mh);
mpg123_exit();
ao_shutdown();
//system("mpg123 -q traklink");
// return 0;
}
void *threading (void *trackid)
{
long tid=(long)trackid;
cout<<"sound plays on:Thread id, "<<tid<<endl;
playaudio(tid);
pthread_exit(NULL);
}
cmakelists:
cmake_minimum_required(VERSION 2.8)
project(emotime)
find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})
FIND_PATH( MPG123_INCLUDE_DIR1
NAMES mpg123.h
PATH_SUFFIXES include
PATHS
~/Library/Frameworks
/Library/Frameworks
/usr/local
/usr
/sw # Fink
/opt/local # DarwinPorts
/opt/csw # Blastwave
/opt
extern/mpg123/ports/MSVC++
extern/mpg123/ports/Xcode
)
IF( MPG123_INCLUDE_DIR1 )
SET( MPG123_INCLUDE_DIRS ${MPG123_INCLUDE_DIRS} ${MPG123_INCLUDE_DIR1} )
ENDIF( MPG123_INCLUDE_DIR1 )
# Include dir (May not be necessary on all platforms)
FIND_PATH( MPG123_INCLUDE_DIR2
NAMES mpg123.h.in
PATHS
~/Library/Frameworks
/Library/Frameworks
/usr/local
/usr
/sw # Fink
/opt/local # DarwinPorts
/opt/csw # Blastwave
/opt
extern/mpg123/src/libmpg123
)
IF( MPG123_INCLUDE_DIR2 )
SET( MPG123_INCLUDE_DIRS ${MPG123_INCLUDE_DIRS} ${MPG123_INCLUDE_DIR2} )
ENDIF( MPG123_INCLUDE_DIR2 )
#MESSAGE( "MPG123_INCLUDE_DIR1: " ${MPG123_INCLUDE_DIR1} )
#MESSAGE( "MPG123_INCLUDE_DIR2: " ${MPG123_INCLUDE_DIR2} )
#MESSAGE( "MPG123_INCLUDE_DIRS: " ${MPG123_INCLUDE_DIRS} )
FIND_LIBRARY( MPG123_LIBRARIES
NAMES mpg123 libmpg123.lib
HINTS
PATH_SUFFIXES lib64 lib libs64 libs libs/Win32 libs/Win64 Release Debug
PATHS
~/Library/Frameworks
/Library/Frameworks
/usr/local
/usr
/sw
/opt/local
/opt/csw
/opt
extern/mpg123/ports/MSVC++/2005
extern/mpg123/ports/MSVC++/2008
extern/mpg123/ports/MSVC++/2008clr
extern/mpg123/ports/MSVC++/2010
)
SET( MPG123_FOUND 0 )
IF( MPG123_LIBRARIES AND MPG123_INCLUDE_DIRS )
SET( MPG123_FOUND 1 )
MESSAGE( STATUS "mpg123 found!" )
ELSE( MPG123_LIBRARIES AND MPG123_INCLUDE_DIRS )
MESSAGE( STATUS "mpg123 not found..." )
ENDIF( MPG123_LIBRARIES AND MPG123_INCLUDE_DIRS )
FIND_PATH(LIBAO_INCLUDE_DIR ao.h /usr/include/ao /usr/local/include/ao)
FIND_LIBRARY(LIBAO_LIBRARIES NAMES ao PATH /usr/lib /usr/local/lib)
IF (LIBAO_INCLUDE_DIR AND LIBAO_LIBRARIES)
SET(LIBAO_FOUND TRUE)
ENDIF (LIBAO_INCLUDE_DIR AND LIBAO_LIBRARIES)
IF (LIBAO_FOUND)
IF (NOT LIBAO_FIND_QUIETLY)
MESSAGE(STATUS "Found libao: ${LIBAO_LIBRARIES}")
ENDIF (NOT LIBAO_FIND_QUIETLY)
ELSE (LIBAO_FOUND)
IF (LIBAO_FIND_REQUIRED)
MESSAGE(FATAL_ERROR "Could not find libao")
ENDIF (LIBAO_FIND_REQUIRED)
ENDIF (LIBAO_FOUND)
include_directories(${LIBAO_INCLUDE_DIR} ${MPG123_INCLUDE_DIRS})
set(ASSETDIR "${emotime_SOURCE_DIR}/assets" )
set(HEADERDIR "${emotime_SOURCE_DIR}/include" )
set(SRCDIR "${emotime_SOURCE_DIR}/src" )
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
add_subdirectory(src
)

Answer 1

In CMake you achieve linking to those libraries using the following commands (don't add the libraries to CXX_FLAGS!):
include_directories(${LIBAO_INCLUDE_DIR} ${MPG123_INCLUDE_DIRS})
target_link_libraries(target_name ${LIBAO_LIBRARIES} ${MPG123_LIBRARIES})
were target_name needs to be replaced by your actual target's name.