Hey all,
Im currently writing on a video player with Qt and I want to use QAudioOutput from the Multimedia module together with ffmpeg. However after decoding the audio data most of the time I just hear noise, below my code:

Qt Code: 
  1. void MainWindow::try_with_ffmpeg()
  2. {
  3.     av_register_all();
  4.  
  5.     int             audioStream = -1;
  6.     AVCodecContext  *codecContext;
  7.     AVCodec         *codec;
  8.     AVPacket        packet;
  9.  
  10.     av_open_input_file(&formatContext, WMV, NULL,0,NULL);
  11.     av_find_stream_info(formatContext);
  12.     av_dump_format(formatContext, 0, WMV,0);
  13.  
  14.     for( unsigned int i=0; i < formatContext->nb_streams; i++ )
  15.     {
  16.         if( formatContext->streams[i]->codec->codec_type == CODEC_TYPE_AUDIO )
  17.         {
  18.             audioStream = i;
  19.             break;
  20.         }
  21.     }
  22.     if( audioStream == -1 )
  23.     {
  24.         qWarning() << "Didnt find audio stream";
  25.         return;
  26.     }
  27.  
  28.     codecContext = formatContext->streams[audioStream]->codec;
  29.  
  30.     codec = avcodec_find_decoder(codecContext->codec_id);
  31.     avcodec_open(codecContext,codec);
  32.  
  33.     med_buffer = (uint8_t*)malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
  34.     buffer.open(QBuffer::WriteOnly);
  35.  
  36.     int i=0;
  37.  
  38.     while( av_read_frame(formatContext,&packet) >= 0 )
  39.     {
  40.         qint64 written=0;
  41.         if( packet.stream_index == audioStream )
  42.         {
  43. //            qDebug() << "reading audio packet";
  44.             int len, data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
  45.             len = avcodec_decode_audio3(codecContext, (int16_t*)med_buffer, &data_size, &packet);
  46.             if( len <= 0 )
  47.                 qWarning() << "no data read to buffer";
  48.             else
  49.             {
  50.                 written = buffer.write((const char*)med_buffer, len);
  51.  
  52.                 qDebug()<< "i= " << ++i << "len = " << len << "\twritten =" << written << "\tbuffer.size() =" << buffer.size();
  53.             }
  54.  
  55.             if( buffer.size() > 10000000 )
  56.             {
  57.                 qDebug() << "buffer.size()=" << buffer.size();
  58.                 break;
  59.             }
  60.  
  61.         }
  62.  
  63.     }
  64.     qDebug() << "bitRate= " << codecContext->bit_rate
  65.              << "\nsampleRate = " << codecContext->sample_rate;
  66.     QAudioFormat format;
  67.     format.setFrequency(codecContext->sample_rate);
  68.     format.setChannels(2);
  69.     format.setSampleSize(16);
  70.     format.setCodec("audio/pcm");
  71.     format.setByteOrder(QAudioFormat::LittleEndian);
  72.     format.setSampleType(QAudioFormat::SignedInt);
  73.  
  74.     QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
  75.     if (!info.isFormatSupported(format)) {
  76.         qWarning()<<"raw audio format not supported by backend, cannot play audio.";
  77.         format = info.nearestFormat(format);
  78.     }
  79.  
  80.     audio = new QAudioOutput(format, this);
  81.  
  82.     connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(stateChanged(QAudio::State)));
  83.  
  84.     if( !buffer.open(QBuffer::ReadWrite) )
  85.         qWarning() << "Couldnt open Buffer";
  86.  
  87.     qDebug() << "buffer.size()=" << buffer.size();
  88.  
  89.     audio->start(&buffer);
  90. }
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If I convert a file with ffmpeg -i bla.ogg -acodec pcm_s16le output.wav to a pcm file, the audio stream is played correctly, however, if I use another codec audio fails.

Any Ideas?