终于解决了那个顽固的问题。运行opencv_example的问题比较复杂，所以有两个步骤来解决：
1链接必要的OpenCV库
我最初的想法是正确的：创建 VLC 视频过滤器失败是由未链接的 OpenCV 库引起的。
要链接它们，请打开 configure.ac 进行编写。然后找到以下行：
PKG_ENABLE_MODULES_VLC([OPENCV], [opencv_example opencv_wrapper], [opencv], (OpenCV (computer vision) filter), [off])
这一行告诉 VLC NOT 将 OpenCV 链接到 opencv_example 和 opencv_wrapper。所以更改它并添加更多行来检查 CV 函数的可用性：
PKG_ENABLE_MODULES_VLC([OPENCV], [opencv_example opencv_wrapper], [opencv], (OpenCV (computer vision) filter), [on])
AC_MSG_CHECKING([opencv libs for opencv_example & opencv_wrapper])
AC_CHECK_LIB(opencv_objdetect, cvHaarDetectObjects,
[
VLC_ADD_PLUGIN([opencv_wrapper opencv_example])
VLC_ADD_CFLAGS([opencv_wrapper opencv_example], [$OPENCV_CFLAGS])
VLC_ADD_LIBS([opencv_wrapper opencv_example],[-lopencv_core -lopencv_objdetect])
AC_MSG_RESULT([opencv libs added, cvHaarDetectObjects is ok])
],
AC_MSG_ERROR([opencv libs for opencv_example & opencv_wrapper cannot be added!]))
保存这个文件，回到VLC目录，进行如下操作：
autoconf
./configure
make
make install
运行 ./configure 时，您的终端应显示的其他信息包括：
checking opencv libs for opencv_example & opencv_wrapper...
checking for cvHaarDetectObjects in -lopencv_objdetect... yes
这是一首好歌，意味着 OpenCV 已安装并且 VLC 已准备好将其链接到我们的插件。
安装完所有东西（make install）后，通过运行 /usr/local/lib/vlc/plugins/video_filter 目录中的 ldd 实用程序检查链接（或无论您的 VLC 插件安装在哪里）：
XXX@XXX:/usr/local/lib/vlc/plugins/video_filter# ldd libopencv_example_plugin.so
linux-vdso.so.1 => (0x00007fff549cd000)
libvlccore.so.5 => /usr/local/lib/libvlccore.so.5 (0x00007f036aa2a000)
libopencv_core.so.2.4 => /usr/local/lib/libopencv_core.so.2.4 (0x00007f036a5e8000)
libopencv_objdetect.so.2.4 => /usr/local/lib/libopencv_objdetect.so.2.4 (0x00007f036a367000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0369fa7000)
libdbus-1.so.3 => /lib/x86_64-linux-gnu/libdbus-1.so.3 (0x00007f0369d63000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f0369b5a000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f036993d000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f0369739000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f036943c000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f0369225000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f0368f25000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f0368d0e000)
libopencv_imgproc.so.2.4 => /usr/local/lib/libopencv_imgproc.so.2.4 (0x00007f036884c000)
libopencv_highgui.so.2.4 => /usr/local/lib/libopencv_highgui.so.2.4 (0x00007f03684ae000)
/lib64/ld-linux-x86-64.so.2 (0x00007f036af2f000)
libjpeg.so.8 => /usr/lib/x86_64-linux-gnu/libjpeg.so.8 (0x00007f036825d000)
libpng12.so.0 => /lib/x86_64-linux-gnu/libpng12.so.0 (0x00007f0368035000)
libtiff.so.4 => /usr/lib/x86_64-linux-gnu/libtiff.so.4 (0x00007f0367dd0000)
libgtk-x11-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0 (0x00007f0367796000)
libgdk-x11-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0 (0x00007f03674e4000)
libgobject-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 (0x00007f0367294000)
libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f0366f9f000)
libdc1394.so.22 => /usr/lib/x86_64-linux-gnu/libdc1394.so.22 (0x00007f0366d2c000)
libv4l1.so.0 => /usr/lib/x86_64-linux-gnu/libv4l1.so.0 (0x00007f0366b25000)
libavcodec.so.53 => /usr/lib/x86_64-linux-gnu/libavcodec.so.53 (0x00007f0365d15000)
libavformat.so.53 => /usr/lib/x86_64-linux-gnu/libavformat.so.53 (0x00007f0365a15000)
libavutil.so.51 => /usr/lib/x86_64-linux-gnu/libavutil.so.51 (0x00007f03657f4000)
libswscale.so.2 => /usr/lib/x86_64-linux-gnu/libswscale.so.2 (0x00007f03655ae000)
libpangocairo-1.0.so.0 => /usr/lib/x86_64-linux-gnu/libpangocairo-1.0.so.0 (0x00007f03653a1000)
libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007f036506c000)
libXfixes.so.3 => /usr/lib/x86_64-linux-gnu/libXfixes.so.3 (0x00007f0364e66000)
libatk-1.0.so.0 => /usr/lib/x86_64-linux-gnu/libatk-1.0.so.0 (0x00007f0364c43000)
libcairo.so.2 => /usr/lib/x86_64-linux-gnu/libcairo.so.2 (0x00007f0364985000)
libgdk_pixbuf-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgdk_pixbuf-2.0.so.0 (0x00007f0364765000)
libgio-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgio-2.0.so.0 (0x00007f0364415000)
libpangoft2-1.0.so.0 => /usr/lib/x86_64-linux-gnu/libpangoft2-1.0.so.0 (0x00007f03641eb000)
libpango-1.0.so.0 => /usr/lib/x86_64-linux-gnu/libpango-1.0.so.0 (0x00007f0363fa2000)
libfontconfig.so.1 => /usr/lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f0363d6b000)
libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007f0363b5a000)
libXrender.so.1 => /usr/lib/x86_64-linux-gnu/libXrender.so.1 (0x00007f0363950000)
libXinerama.so.1 => /usr/lib/x86_64-linux-gnu/libXinerama.so.1 (0x00007f036374c000)
libXi.so.6 => /usr/lib/x86_64-linux-gnu/libXi.so.6 (0x00007f036353d000)
libXrandr.so.2 => /usr/lib/x86_64-linux-gnu/libXrandr.so.2 (0x00007f0363335000)
libXcursor.so.1 => /usr/lib/x86_64-linux-gnu/libXcursor.so.1 (0x00007f036312a000)
libXcomposite.so.1 => /usr/lib/x86_64-linux-gnu/libXcomposite.so.1 (0x00007f0362f27000)
libXdamage.so.1 => /usr/lib/x86_64-linux-gnu/libXdamage.so.1 (0x00007f0362d24000)
libffi.so.6 => /usr/lib/x86_64-linux-gnu/libffi.so.6 (0x00007f0362b1b000)
libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f03628de000)
libraw1394.so.11 => /usr/lib/x86_64-linux-gnu/libraw1394.so.11 (0x00007f03626ce000)
libusb-1.0.so.0 => /lib/x86_64-linux-gnu/libusb-1.0.so.0 (0x00007f03624bf000)
libv4l2.so.0 => /usr/lib/x86_64-linux-gnu/libv4l2.so.0 (0x00007f03622b3000)
libvpx.so.1 => /usr/lib/libvpx.so.1 (0x00007f036200d000)
libvorbisenc.so.2 => /usr/lib/x86_64-linux-gnu/libvorbisenc.so.2 (0x00007f0361b3e000)
libvorbis.so.0 => /usr/lib/x86_64-linux-gnu/libvorbis.so.0 (0x00007f0361912000)
libtheoraenc.so.1 => /usr/lib/x86_64-linux-gnu/libtheoraenc.so.1 (0x00007f03616d4000)
libtheoradec.so.1 => /usr/lib/x86_64-linux-gnu/libtheoradec.so.1 (0x00007f03614b9000)
libspeex.so.1 => /usr/lib/x86_64-linux-gnu/libspeex.so.1 (0x00007f03612a0000)
libschroedinger-1.0.so.0 => /usr/lib/libschroedinger-1.0.so.0 (0x00007f0360fec000)
libgsm.so.1 => /usr/lib/libgsm.so.1 (0x00007f0360dde000)
libva.so.1 => /usr/lib/x86_64-linux-gnu/libva.so.1 (0x00007f0360bc8000)
libbz2.so.1.0 => /lib/x86_64-linux-gnu/libbz2.so.1.0 (0x00007f03609b7000)
libfreetype.so.6 => /usr/lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f036071b000)
libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f03604fc000)
libpixman-1.so.0 => /usr/lib/x86_64-linux-gnu/libpixman-1.so.0 (0x00007f0360275000)
libxcb-shm.so.0 => /usr/lib/x86_64-linux-gnu/libxcb-shm.so.0 (0x00007f0360072000)
libxcb-render.so.0 => /usr/lib/x86_64-linux-gnu/libxcb-render.so.0 (0x00007f035fe67000)
libgmodule-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgmodule-2.0.so.0 (0x00007f035fc63000)
libselinux.so.1 => /lib/x86_64-linux-gnu/libselinux.so.1 (0x00007f035fa43000)
libresolv.so.2 => /lib/x86_64-linux-gnu/libresolv.so.2 (0x00007f035f827000)
libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f035f5fc000)
libv4lconvert.so.0 => /usr/lib/x86_64-linux-gnu/libv4lconvert.so.0 (0x00007f035f387000)
libogg.so.0 => /usr/lib/x86_64-linux-gnu/libogg.so.0 (0x00007f035f180000)
liborc-0.4.so.0 => /usr/lib/x86_64-linux-gnu/liborc-0.4.so.0 (0x00007f035ef04000)
libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007f035ed01000)
libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f035eafb000)
你看，链接库的数量增加了几倍。
第一步完成。您可以通过运行 VLC 检查 opencv_example 的加载。但是你可能会面临另一个问题：
...
[0x7f2d741728f8] main video output debug: Adding 'opencv_example' as interactive
[0x7f2d747f7a68] main filter debug: looking for video filter2 module: 1 candidate
[0x7f2d747f7a68] main filter debug: using video filter2 module "opencv_example"
[0x7f2d747f7a68] main filter debug: TIMER module_need() : 149.351 ms - Total 149.351 ms / 1 intvls (Avg 149.351 ms)
[0x7f2d741728f8] main video output debug: Filter 'opencv_example' (0x7f2d747f7a68) appended to chain
[0x7f2d74173cb8] main spu text debug: removing module "freetype"
[0x7f2d74173cb8] main spu text debug: looking for text renderer module: 3 candidates
[0x7f2d74173cb8] freetype spu text debug: Building font databases.
[0x7f2d74173cb8] freetype spu text debug: Took 33 microseconds
[0x7f2d74173cb8] freetype spu text debug: Using Serif Bold as font from file /usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf
[0x7f2d74173cb8] freetype spu text debug: using fontsize: 2
[0x7f2d74173cb8] main spu text debug: using text renderer module "freetype"
[0x7f2d74173cb8] main spu text debug: TIMER module_need() : 5.776 ms - Total 5.776 ms / 1 intvls (Avg 5.776 ms)
[0x7f2d8c00d018] main decoder debug: End of video preroll
[0x7f2d8c00d018] main decoder debug: Received first picture
Segmentation fault (core dumped)
2 更改 opencv_example 源代码
因此，正如我所发现的，将图像从 picture_t（用于存储图像的 VLC 结构）转换为 IplImage（用于图像的 OpenCV 类型）时隐藏了错误：
//(hack) cast the picture_t to array of IplImage*
p_img = (IplImage**) p_pic->p[0].p_pixels;
只需稍微更改此转换即可使一切正常运行。这是我修改的 opencv_example.c 中 Filter 方法的完整代码：
static picture_t *Filter( filter_t *p_filter, picture_t *p_pic )
{
IplImage* p_img;
int i_planes = 0;
CvPoint pt1, pt2;
int i, scale = 1;
filter_sys_t *p_sys = p_filter->p_sys;
if ((!p_pic))
{
msg_Err( p_filter, "no image array" );
return NULL;
}
i_planes = p_pic->i_planes;
if (i_planes<1)
{
msg_Err( p_filter, "no image planes" );
return NULL;
}
if ((p_pic->format.i_chroma != VLC_CODEC_I420))
{
msg_Err( p_filter, "wrong chroma - use I420" );
return NULL;
}
//picture_t to IplImage without segmentation fault
p_img = cvCreateImageHeader( cvSize( p_pic->p[0].i_pitch, p_pic->p[0].i_visible_lines ),
IPL_DEPTH_8U, 1 );
cvSetData( p_img, p_pic->p[0].p_pixels, p_pic->p[0].i_pitch );
//perform face detection
cvClearMemStorage(p_sys->p_storage);
if( p_sys->p_cascade )
{
//we should make some of these params config variables
CvSeq *faces = cvHaarDetectObjects( p_img, p_sys->p_cascade, p_sys->p_storage,
1.15, 5, CV_HAAR_DO_CANNY_PRUNING,
cvSize(0, 0), cvSize(20, 20) );
//create the video_filter_region_info_t struct
if (faces && (faces->total > 0))
{
msg_Dbg( p_filter, "Found %d face(s)", faces->total );
free( p_sys->event_info.p_region );
p_sys->event_info.p_region = (video_filter_region_info_t*)
calloc( faces->total, sizeof(video_filter_region_info_t));
if( !p_sys->event_info.p_region )
return NULL;
p_sys->event_info.i_region_size = faces->total;
}
//populate the video_filter_region_info_t struct
for( i = 0; i < (faces ? faces->total : 0); i++ )
{
CvRect *r = (CvRect*)cvGetSeqElem( faces, i );
pt1.x = r->x*scale;
pt2.x = (r->x+r->width)*scale;
pt1.y = r->y*scale;
pt2.y = (r->y+r->height)*scale;
cvRectangle( p_img, pt1, pt2, CV_RGB(0,0,0), 3, 8, 0 );
*(CvRect*)(&(p_sys->event_info.p_region[i])) = *r;
p_sys->event_info.p_region[i].i_id = p_sys->i_id++;
p_sys->event_info.p_region[i].p_description = "Face Detected";
}
if (faces && (faces->total > 0)) //raise the video filter event
var_TriggerCallback( p_filter->p_libvlc, VIDEO_FILTER_EVENT_VARIABLE );
}
else
msg_Err( p_filter, "No cascade - is opencv-haarcascade-file valid?" );
//IplImage to picture_t without segmentation fault
cvGetRawData( p_img, (uchar**)&p_pic->p[0].p_pixels, NULL, NULL );
return p_pic;
}
VLC 和 opencv_example 过滤器应该都能正常工作。如果您还有其他与 VLC+OpenCV 主题相关的问题，请告诉我