Qt Mobility/Qmediaplayer/windows 7-dshow doesn't play QIODevice (QBuffer)

using QMediaPlayer class to play audio from memory. *.ogg, *.flac, *.wma, *.wav (mono 88kbps) could not be played when using QBuffer.

//QBuffer *buffer
//QMediaPlayer *player

QFile f ( filename );
f.open( QIODevice::ReadOnly );
if( buffer->isOpen() ) buffer->close();
buffer->setData( f.readAll());
buffer->open( QIODevice::ReadOnly );
player->setMedia( QMediaContent( ), buffer);
player->play();

but

player->setMedia( QMediaContent( QUrl::fromLocalFile( filename ) ));

work fine.

sample files:
1/http://upload.wikimedia.org/wikipedia/commons/5/56/En-uk-hear.ogg
2/Attachment