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-webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; " class=""><div class="">--</div><div class="">Perette Barella • <a href="mailto:perette@barella.org" class="">perette@barella.org</a> • 585-286-1312</div><div class="">176 Middlesex Road, Rochester NY 14610</div></div></span></div></span></div></span></div></span></div></span></div></span></div></span></div></span></span>
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<br class=""><div><blockquote type="cite" class=""><div class="">On 2016年09月02日, at 23:54, R n <<a href="mailto:flynewdream@hotmail.com" class="">flynewdream@hotmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div id="divtagdefaultwrapper" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; font-size: 12pt; background-color: rgb(255, 255, 255); font-family: Calibri, Arial, Helvetica, sans-serif;" class=""><div style="margin-top: 0px; margin-bottom: 0px;" class="">Thanks <span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class="">Perette.</span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class=""><br class=""></span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class="">I did exactly what you suggested for the C and C++ files. (I have two header files, one for C and another is for C++, and the C++<span class="Apple-converted-space"> </span><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class="">header file</span> includes the C header file. I have one cpp file in which I put the C and C++ source code. I can also split them into two cpp files for clarity). I guess perhaps the problem is in the how I compile the library and how I compile FFmpeg when I call the library from FFmpeg.</span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class=""><br class=""></span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class="">Any suggestions?</span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class=""><br class=""></span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class="">Thanks.</span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class=""><br class=""></span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><span style="font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol', 'Android Emoji', EmojiSymbols; font-size: 16px;" class="">Rich </span></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div><div id="Signature" class=""><div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div></div><br class=""><br class=""><div style="" class=""><hr tabindex="-1" style="display: inline-block; width: 992.734375px;" class=""><div id="divRplyFwdMsg" dir="ltr" class=""><font face="Calibri, sans-serif" style="font-size: 11pt;" class=""><b class="">发件人:</b><span class="Apple-converted-space"> </span>Libav-user <<a href="mailto:libav-user-bounces@ffmpeg.org" class="">libav-user-bounces@ffmpeg.org</a>> 代表 Perette Barella <<a href="mailto:perette@barella.org" class="">perette@barella.org</a>><br class=""><b class="">发送时间:</b><span class="Apple-converted-space"> </span>2016年9月3日 3:38<br class=""><b class="">收件人:</b><span class="Apple-converted-space"> </span>This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter.<br class=""><b class="">主题:</b><span class="Apple-converted-space"> </span>Re: [Libav-user] Are there any ways to use a lib (built from C++ OpenCV) in Ffmpeg filter?</font><div class=""> </div></div><div class=""><div class=""><blockquote type="cite" class=""><div class="">On 2016年09月02日, at 22:32, R n <<a href="mailto:flynewdream@hotmail.com" class="">flynewdream@hotmail.com</a>> wrote:</div><div class=""><div id="divtagdefaultwrapper" class="" style="font-style: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; font-size: 12pt; background-color: rgb(255, 255, 255); font-family: Calibri, Arial, Helvetica, sans-serif;"><div class="" style="margin-top: 0px; margin-bottom: 0px;"><span class="s1">I am writing a C++ library which is based on OpenCV. I want to use it in a Ffmpeg filter (written in C), so I write a wrapper of the library using C. The wrapper consists of a C header file and some C functions which call the C++ functions (in the C++ files). I expect the FFmpeg filter to only include the C header and call the C functions.</span></div></div></div></blockquote><span class="" style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; background-color: rgb(255, 255, 255);">…</span><br class=""><blockquote type="cite" class=""><div class=""><div id="divtagdefaultwrapper" class="" style="font-style: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; font-size: 12pt; background-color: rgb(255, 255, 255); font-family: Calibri, Arial, Helvetica, sans-serif;"><div class="" style="margin-top: 0px; margin-bottom: 0px;"><span class="s1"></span></div><div class="" style="margin-top: 0px; margin-bottom: 0px;"><span class="s1">However, I get the following error when compiling FFmpeg:</span></div><div class="" style="margin-top: 0px; margin-bottom: 0px;"><span class="s1">.../binutils/2.25/centos6-native/da39a3e/bin/ld: .../mylibrary/0.1/gcc-4.9-glibc-2.20/80414d5/lib/libmylibrary.a(mylibrary_file.cpp.o): undefined reference to symbol '_ZdlPv@@GLIBCXX_3.4'</span></div><div class="" style="margin-top: 0px; margin-bottom: 0px;"><span class="s1">.../libgcc/4.9.x/gcc-4.9-glibc-2.20/024dbc3/lib/libstdc++.so: error adding symbols: DSO missing from command line</span></div></div></div></blockquote><div class=""><br class=""></div><div class="">Your approach is correct, but C++ “mangles” function names to make them unique when considering parameters and such. You need to specify C linkage, so in your .h file, wrap it in extern “C”:</div></div><div class=""><br class=""></div><div class=""><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">#ifdef __cplusplus</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">#warning is c++</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">extern "C" {</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">#endif</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class=""><span class="Apple-tab-span" style="white-space: pre;"></span>char foo (int);</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier; min-height: 14px;"><span class=""></span><br class=""></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">#ifdef __cplusplus</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">}</span></div><div class="" style="margin: 0px; line-height: normal; font-family: Courier;"><span class="">#endif</span></div></div><div class=""><span class=""><br class=""></span></div><div class="">You need to #include the .h file in the corresponding .cpp file, so the C++ compiler knows not to mangle those particular function names when they’re compiled.</div><div class=""><br class=""></div><div class="">Perette</div><div class=""><br class=""></div><div class=""><br class=""></div></div></div></div><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Libav-user mailing list</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="mailto:Libav-user@ffmpeg.org" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Libav-user@ffmpeg.org</a><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="http://ffmpeg.org/mailman/listinfo/libav-user" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">http://ffmpeg.org/mailman/listinfo/libav-user</a></div></blockquote></div><br class=""></body></html>