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• How to add Qt to an existing C program and compile ?

  26 juin 2015, par El Sampsa

  I have a small Qt program I have compiled with qmake and make. When I launch make, I get the following commands for compilation :

  g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++-64 -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I/usr/lib/x86_64-linux-gnu -I/usr/include/SDL -I. -o simpleqt.o simpleqt.cpp

  (.. lets call that (**)) and

  g++ -m64 -Wl,-O1 -o qt simpleqt.o -L/usr/lib/x86_64-linux-gnu -lSDL -lX11 -lQtGui -lQtCore -lpthread

  .. and the program is compiled without problems.

  On the other hand, I have the ffmpeg library which has the "ffplay" program. I want to put some Qt things into ffplay. In the ffmpeg config files I tell to the make process (using "common.mak") that it should be verbose and when issuing "make ffplay", it gives me the following monster :

  gcc -I. -I./ -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600 -DZLIB_CONST -I/home/sampsa/ffmpeg/build/include -std=c99 -fomit-frame-pointer -pthread -I/usr/include/freetype2 -I/usr/include/fribidi -I/usr/include/freetype2 -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -g -Wdeclaration-after-statement -Wall -Wdisabled-optimization -Wpointer-arith -Wredundant-decls -Wwrite-strings -Wtype-limits -Wundef -Wmissing-prototypes -Wno-pointer-to-int-cast -Wstrict-prototypes -Wempty-body -Wno-parentheses -Wno-switch -Wno-format-zero-length -Wno-pointer-sign -O3 -fno-math-errno -fno-signed-zeros -fno-tree-vectorize -Werror=format-security -Werror=implicit-function-declaration -Werror=missing-prototypes -Werror=return-type -Werror=vla -Wformat -Wno-maybe-uninitialized -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -MMD -MF ffplay.d -MT ffplay.o -c -o ffplay.o ffplay.c

  (lets call that monster (++)).

  So far, so good, I have two commands, one (**) for compiling Qt programs and another one (++) for another project (in this case, ffmpeg’s ffplay)

  How do I combine these two ?

  I have tried merging the flags in (**) into command (++). It compiles OK, but the moment I am adding

  #include <qtgui> 
  
  </qtgui>

  into "ffplay.c", all hell breaks loose and the compiler tells me (among many other things) :

  In file included from /usr/include/qt4/QtCore/qobjectdefs.h:45:0,
  from /usr/include/qt4/QtCore/qobject.h:47,
  from /usr/include/qt4/QtCore/qabstracteventdispatcher.h:45,
  from /usr/include/qt4/QtCore/QtCore:3,
  from /usr/include/qt4/QtGui/QtGui:3,
  from ffplay2.c:61 :
  /usr/include/qt4/QtCore/qnamespace.h:51:1 : warning : return type defaults to ‘int’ [enabled by default]
  QT_MODULE(Core)
  ^
  /usr/include/qt4/QtCore/qnamespace.h:51:1 : warning : function declaration isn’t a prototype [-Wstrict-prototypes]
  /usr/include/qt4/QtCore/qnamespace.h : In function ‘QT_MODULE’ :
  /usr/include/qt4/QtCore/qnamespace.h:54:1 : error : unknown type name ‘namespace’
  namespace
  ^
  ...
  ...

  If I combine flags in (**) to (++) and change the compiler from "gcc" to "g++", I get all kinds of errors, this time related to the "ffplay.c" source code.

  What is going on ?

• video hosting with PHP api or PHP script for social network project

  17 avril 2014, par al404IT

  I have a project for a small social network where user can upload their videos, video should not be longer than 1 or 2 minutes but they need to be private and related to user that uploaded.

  Since uploaded video may be in many different format I have two options :

  • upload video and use ffmpeg to process them, can i find any PHP script that does that ? PROS I have my files on my server and I'm not dependent from third party CONS I guess is a real intensive task and I may need a quite good noting plan since the beginning of this project

  • use a video hosting service that provide API to upload and process video, i actually find vzaar.com that may seems to do what I need. PROS Scalable CONS I rely on third party for my contents

  since the project is a small social network it may be interesting this too opusphp.com, but i never user or read about

  can Vimeo PRO suite my needs ? Other suggestions ?
  In future it may be necessary to add a basic video editing function to trim uploaded video setting starting and ending point

• How convert High bitrate mp3 to lower rate using ffmpeg in android

  23 mars 2018, par Android Team

  We want to convert 320kbps mp3 file to 128kbps mp3 so currently we are using below ffmpeg command but its not working.

  ffmpeg -i input.mp3 -codec:a libmp3lame -qscale:a 5 output.mp3

  Result :-the output bitrate same as input mp3.

  And we are following the FFmpeg Encoding guideline for that here is the link :- https://trac.ffmpeg.org/wiki/Encode/MP3

  so please suggest any solution.