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Thread: QAudioOutput + FFMPEG

  1. 29th August 2011, 13:28 #1
    Biberbaer
    Biberbaer is offline Beginner
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    Default QAudioOutput + FFMPEG

    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?
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  2. 30th August 2011, 14:22 #2
    Biberbaer
    Biberbaer is offline Beginner
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    Default Re: QAudioOutput + FFMPEG

    Ok solved the problem by myself:

    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.     while( av_read_frame(formatContext,&packet) >= 0 )
    37.     {
    38.         qint64 written=0;
    39.         if( packet.stream_index == audioStream )
    40.         {
    41.             qDebug() << "size= " << packet.size;
    42.             while(packet.size > 0)
    43.             {
    44.                 int len, data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
    45.                 //decode
    46.                 len = avcodec_decode_audio3(codecContext, (int16_t*)med_buffer, &data_size, &packet);
    47.                 if( len <= 0 )
    48.                     qWarning() << "no data read to buffer";
    49.                 if( data_size > 0 )
    50.                     written = buffer.write((const char*)med_buffer, data_size);
    51.  
    52.                 packet.size -= len;
    53.                 packet.data += len;
    54.  
    55.                 if( buffer.size() > 10000000 )
    56.                 {
    57.                     qDebug() << "buffer.size()=" << buffer.size();
    58.                     break;
    59.                 }
    60.             }
    61.  
    62.         }
    63.  
    64.     }
    65.  
    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.  
    76.     if (!info.isFormatSupported(format)) {
    77.         qWarning()<<"raw audio format not supported by backend, cannot play audio.";
    78.         format = info.nearestFormat(format);
    79.     }
    80.  
    81.     audio = new QAudioOutput(format, this);
    82.  
    83.     connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(stateChanged(QAudio::State)));
    84.  
    85.     if( !buffer.open(QBuffer::ReadWrite) )
    86.         qWarning() << "Couldnt open Buffer";
    87.  
    88.     qDebug() << "buffer.size()=" << buffer.size();
    89.  
    90.     audio->start(&buffer);
    91. }
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  3. 20th June 2014, 10:25 #3
    rsafir
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    Default Re: QAudioOutput + FFMPEG

    Hello,

    I'm trying to use FFMPEG for an audio converter but i can't import the libraries. Can you attach the code to see how you did it?

    Thank you very much!
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  4. 14th January 2015, 01:46 #4
    inforathinam
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    Default Re: QAudioOutput + FFMPEG

    I would like to create sample audio player...Could you pls send me the full code....


    Quote Originally Posted by Biberbaer View Post
    Ok solved the problem by myself:

    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.     while( av_read_frame(formatContext,&packet) >= 0 )
    37.     {
    38.         qint64 written=0;
    39.         if( packet.stream_index == audioStream )
    40.         {
    41.             qDebug() << "size= " << packet.size;
    42.             while(packet.size > 0)
    43.             {
    44.                 int len, data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
    45.                 //decode
    46.                 len = avcodec_decode_audio3(codecContext, (int16_t*)med_buffer, &data_size, &packet);
    47.                 if( len <= 0 )
    48.                     qWarning() << "no data read to buffer";
    49.                 if( data_size > 0 )
    50.                     written = buffer.write((const char*)med_buffer, data_size);
    51.  
    52.                 packet.size -= len;
    53.                 packet.data += len;
    54.  
    55.                 if( buffer.size() > 10000000 )
    56.                 {
    57.                     qDebug() << "buffer.size()=" << buffer.size();
    58.                     break;
    59.                 }
    60.             }
    61.  
    62.         }
    63.  
    64.     }
    65.  
    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.  
    76.     if (!info.isFormatSupported(format)) {
    77.         qWarning()<<"raw audio format not supported by backend, cannot play audio.";
    78.         format = info.nearestFormat(format);
    79.     }
    80.  
    81.     audio = new QAudioOutput(format, this);
    82.  
    83.     connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(stateChanged(QAudio::State)));
    84.  
    85.     if( !buffer.open(QBuffer::ReadWrite) )
    86.         qWarning() << "Couldnt open Buffer";
    87.  
    88.     qDebug() << "buffer.size()=" << buffer.size();
    89.  
    90.     audio->start(&buffer);
    91. }
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  5. 16th January 2015, 17:28 #5
    Kryzon
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    Default Re: QAudioOutput + FFMPEG

    His post is from 2011, it's not likely that he'll read your request.

    You may want to look at the following:

    - Qt Phonon (4.8) music player example.
    http://qt-project.org/doc/qt-4.8/pho...sicplayer.html

    - Amarok, an advanced open source audio player built with Qt.
    https://amarok.kde.org/en/contribute

    - MLT Framework, a multimedia framework that can be used along with Qt.
    http://www.mltframework.org/bin/view/MLT/Features
    https://github.com/mltframework/BuildOnMe (simple Qt example)
    https://github.com/mltframework/shotcut
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