mpg123 library with Qt - qt

Question

I want add support for playback of mp3 file in my Qt app for embedded linux.
I'm not able to use phonon in Qt. After adding QT += phonon in .pro file it gives me the following error during compilation :
/usr/lib/gcc/i486-linux-gnu/4.4.1/../../../../lib/libphonon.so: undefined reference to `QWidget::x11Event(_XEvent*)'
/usr/lib/gcc/i486-linux-gnu/4.4.1/../../../../lib/libphonon.so: undefined reference to `QDataStream::QDataStream(QByteArray*, int)'
collect2: ld returned 1 exit status
So now i'm thinking of using the mpg123 lib for decoding mp3 files.
I need help integrating the library in Qt. I've never used a pure c++ library in Qt before so i don't have much idea on how to integrate it.

Answer 1

Hey all !! Finally I figured it out !!
int MP3Player::Init(const char *pFileName)
{
mpg123_init();
m_mpgHandle = mpg123_new(0, 0);
if(mpg123_open(m_mpgHandle, pFileName) != MPG123_OK)
{
qFatal("Cannot open %s: %s", pFileName, mpg123_strerror(m_mpgHandle));
return 0;
}
}
int MP3Player::Play()
{
unsigned char *audio;
int mc;
size_t bytes;
qWarning("play_frame");
static unsigned char* arr = 0;
/* The first call will not decode anything but return MPG123_NEW_FORMAT! */
mc = mpg123_decode_frame(m_mpgHandle, &m_framenum, &audio, &bytes);
if(bytes)
{
/* Normal flushing of data, includes buffer decoding. */
/*This function is my already implemented audio class which uses ALSA to output decoded audio to Sound Card*/
if (m_audioPlayer.Play(arr,bytes) < (int)bytes)
{
qFatal("Deep trouble! Cannot flush to my output anymore!");
}
}
/* Special actions and errors. */
if(mc != MPG123_OK)
{
if(mc == MPG123_ERR)
{
qFatal("...in decoding next frame: %s", mpg123_strerror(m_mpgHandle));
return CSoundDecoder::EOFStream;
}
if(mc == MPG123_DONE)
{
return CSoundDecoder::EOFStream;
}
if(mc == MPG123_NO_SPACE)
{
qFatal("I have not enough output space? I didn't plan for this.");
return CSoundDecoder::EOFStream;
}
if(mc == MPG123_NEW_FORMAT)
{
long iFrameRate;
int encoding;
mpg123_getformat(m_mpgHandle, &iFrameRate, &m_iChannels, &encoding);
m_iBytesPerChannel = mpg123_encsize(encoding);
if (m_iBytesPerChannel == 0)
qFatal("bytes per channel is 0 !!");
m_audioPlayer.Init(m_iChannels , iFrameRate , m_iBytesPerChannel);
}
}
}

Answer 2

In order to get mpg123 working with your QT project you try following steps:
1.download and install mpg123: from the folder where you extracted it to (e.g /home/mpg123-1.13.0/) run ./configure and then "sudo make install"
2.if there are no errors put this line to your *.pro file
LIBS += /usr/local/lib/libmpg123.so
3.then code below should run fine for you:
#include "mpg123.h"
#include <QDebug>
void MainWindow::on_pushButton_2_clicked()
{
const char **decoders = mpg123_decoders();
while (*decoders != NULL)
{
qDebug() << *decoders;
decoders++;
}
}
alternatively you can call mpg123 via system call:
system("mpg123 /home/test.mp3");
hope this helps, regards