交叉编译支持多线程的Android版X264库

博客原文：http://bashell.sinaapp.com/archives/cross-complie-pthread-android-x264-library.html

第一步,制作独立交叉编译链,我使用ndkr9制作的, 使用API 9平台,gcc4.6
进入ndk目录,执行

$ ./build/tools/make-standalone-toolchain.sh --platform=android-9 --install-dir=/home/aliang/arm-linux-androideabi

第二部,修改x264的configure

libpthread=""if [ "$thread" = "auto" ]; then    thread="no"    case $SYS in        BEOS)            thread="beos"            define HAVE_BEOSTHREAD            ;;        WINDOWS)            if cc_check pthread.h -lpthread "pthread_create(0,0,0,0);" ; then                thread="posix"                libpthread="-lpthread"            elif cc_check pthread.h -lpthreadGC2 "pthread_create(0,0,0,0);" ; then                thread="posix"                libpthread="-lpthreadGC2"            elif cc_check pthread.h "-lpthreadGC2 -lwsock32 -DPTW32_STATIC_LIB" "pthread_create(0,0,0,0);" ; then                thread="posix"                libpthread="-lpthreadGC2 -lwsock32"                define PTW32_STATIC_LIB            elif cc_check pthread.h "-lpthreadGC2 -lws2_32 -DPTW32_STATIC_LIB" "pthread_create(0,0,0,0);" ; then                thread="posix"                libpthread="-lpthreadGC2 -lws2_32"                define PTW32_STATIC_LIB            else                # default to native threading if pthread-win32 is unavailable                thread="win32"            fi            ;;        QNX)            cc_check pthread.h -lc && thread="posix" && libpthread="-lc"            ;;        *)            //这里            cc_check pthread.h -lc && thread="posix" && libpthread="-lc"            ;;    esacfi

改为红色行的内容,因为android的ndk虽然有pthread.h,但是没有libpthread.a,集成到libc.a里了

第三步,定位到制作的独立编译链的头文件目录 /home/aliang/arm-linux-androideabi/sysroot/usr/include/
使用这个sched.h替换原有的sched.h文件

ok
./configure –host=arm-linux-androideabi –cross-prefix=arm-linux-androideabi-
可以看到,已经支持多线程了

platform:      ARMsystem:        LINUXcli:           yeslibx264:       internalshared:        nostatic:        noasm:           yesinterlaced:    yesavs:           avxsynthlavf:          noffms:          nogpac:          nogpl:           yesthread:        posixopencl:        yesfilters:       crop select_everydebug:         nogprof:         nostrip:         noPIC:           novisualize:     nobit depth:     8chroma format: all

效果如何,我测试下看看

*************呃 不用试了,NDK头文件里虽然申明了方法,c库里却没有实现****************

好吧 解决方法当然是有的,修改x264/common/cpu.c
通过读取/sys/devices/system/cpu/present文件判断cpu核心数
0 单核
0-1 双核
0-3 四核
sched.h还是用以前的吧

博主注：

int x264_cpu_num_processors( void )

这个函数在ffmpeg2.1里面的原型已经不是上面那么简单了。

int x264_cpu_num_processors( void ){#if !HAVE_THREAD    return 1;#elif SYS_WINDOWS    return x264_pthread_num_processors_np();#elif SYS_CYGWIN || SYS_SunOS    return sysconf( _SC_NPROCESSORS_ONLN );#elif SYS_LINUX    cpu_set_t p_aff;    memset( &p_aff, 0, sizeof(p_aff) );    if( sched_getaffinity( 0, sizeof(p_aff), &p_aff ) )        return 1;#if HAVE_CPU_COUNT    return CPU_COUNT(&p_aff);#else    int np = 0;    for( unsigned int bit = 0; bit < 8 * sizeof(p_aff); bit++ )        np += (((uint8_t *)&p_aff)[bit / 8] >> (bit % 8)) & 1;    return np;#endif#elif SYS_BEOS    system_info info;    get_system_info( &info );    return info.cpu_count;#elif SYS_MACOSX || SYS_FREEBSD || SYS_OPENBSD    int ncpu;    size_t length = sizeof( ncpu );#if SYS_OPENBSD    int mib[2] = { CTL_HW, HW_NCPU };    if( sysctl(mib, 2, &ncpu, &length, NULL, 0) )#else    if( sysctlbyname("hw.ncpu", &ncpu, &length, NULL, 0) )#endif    {        ncpu = 1;    }    return ncpu;#else    return 1;#endif}

替换其中的这段代码代码就行了。

    cpu_set_t p_aff;    memset( &p_aff, 0, sizeof(p_aff) );    if( sched_getaffinity( 0, sizeof(p_aff), &p_aff ) )        return 1;#if HAVE_CPU_COUNT    return CPU_COUNT(&p_aff);#else    int np = 0;    for( unsigned int bit = 0; bit < 8 * sizeof(p_aff); bit++ )        np += (((uint8_t *)&p_aff)[bit / 8] >> (bit % 8)) & 1;    return np;