What do operation system you use? Version of Qt? And, please, show your .pro file.

Qt version :4.7.1 on linux system (ubuntu 10.10) this is the .pro file

i added this lines :
1-QT +=multimedia
2-INCLUDEPATH +=/home/aladin/QtSDK/Desktop/Qt/473/gcc/include/QtMultimedia/
3-INCLUDEPATH +=/home/aladin/QtSDK/Desktop/Qt/473/gcc/include/
4-LIBS +=/home/aladin/QtSDK/QtCreator/lib/qtcreator/libQtMultimedia.so

INCLUDEPATH +=/home/aladin/QtSDK/Desktop/Qt/473/gcc/include/QtMultimedia/
INCLUDEPATH +=/home/aladin/QtSDK/Desktop/Qt/473/gcc/include/
LIBS +=/home/aladin/QtSDK/QtCreator/lib/qtcreator/libQtMultimedia.so

Not needed lines.

without line 2 and 3 i m not even to compile the program , and the compiler didn’t recognize QAudioInput and QAudioFormat

Ubuntu doesn’t have qt-multimedia anymore.

Ok remove only this line:
LIBS +=/home/aladin/QtSDK/QtCreator/lib/qtcreator/libQtMultimedia.so

Smar wrote:

Ubuntu doesn’t have qt-multimedia anymore.

so what should i do ? is there a solution to install it in ubuntu 10.10 ?

I have no idea why Ubuntu guys did that, but you can use qt-mobility’s qt-multimedia(it is the real multimedia package that will be in Qt 4.8 or so instead of that dummy one that’s in 4.6 and 4.7).

I installed the qt-mobility and still get the same error or is there new class to use ?

It is most likely in different package; you need to include it with QT += multimedia… Really, read its documentation, the forum is not substitute to doc. http://doc.qt.nokia.com/qtmobility-1.1/index.html

I also got crazy with this error, and the documentation really didn’t help.
Combining serveral posts on other forums, and with trial and error, I needed following steps to get the multimedia compiling and running again under Ubuntu.
(In the .pro file)
QT += mobility multimediakit
CONFIG += mobility
MOBILITY = multimedia
… and also remove the QT += multimedia

Oops. And also add

INCLUDEPATH += /usr/include/QtMobility
INCLUDEPATH += /usr/include/QtMultimediaKit