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:

Code:

---

void MainWindow::try_with_ffmpeg()
{
    av_register_all();
 
    int             audioStream = -1;
    AVCodecContext  *codecContext;
    AVCodec         *codec;
    AVPacket        packet;
 
    av_open_input_file(&formatContext, WMV, NULL,0,NULL);
    av_find_stream_info(formatContext);
    av_dump_format(formatContext, 0, WMV,0);
 
    for( unsigned int i=0; i < formatContext->nb_streams; i++ )
    {
        if( formatContext->streams[i]->codec->codec_type == CODEC_TYPE_AUDIO )
        {
            audioStream = i;
            break;
        }
    }
    if( audioStream == -1 )
    {
        qWarning() << "Didnt find audio stream";
        return;
    }
 
    codecContext = formatContext->streams[audioStream]->codec;
 
    codec = avcodec_find_decoder(codecContext->codec_id);
    avcodec_open(codecContext,codec);
 
    med_buffer = (uint8_t*)malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
    buffer.open(QBuffer::WriteOnly);
 
    int i=0;
 
    while( av_read_frame(formatContext,&packet) >= 0 )
    {
        qint64 written=0;
        if( packet.stream_index == audioStream )
        {
//            qDebug() << "reading audio packet";
            int len, data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
            len = avcodec_decode_audio3(codecContext, (int16_t*)med_buffer, &data_size, &packet);
            if( len <= 0 )
                qWarning() << "no data read to buffer";
            else
            {
                written = buffer.write((const char*)med_buffer, len);
 
                qDebug()<< "i= " << ++i << "len = " << len << "\twritten =" << written << "\tbuffer.size() =" << buffer.size();
            }
 
            if( buffer.size() > 10000000 )
            {
                qDebug() << "buffer.size()=" << buffer.size();
                break;
            }
 
        }
 
    }
    qDebug() << "bitRate= " << codecContext->bit_rate
             << "\nsampleRate = " << codecContext->sample_rate;
    QAudioFormat format;
    format.setFrequency(codecContext->sample_rate);
    format.setChannels(2);
    format.setSampleSize(16);
    format.setCodec("audio/pcm");
    format.setByteOrder(QAudioFormat::LittleEndian);
    format.setSampleType(QAudioFormat::SignedInt);
 
    QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
    if (!info.isFormatSupported(format)) {
        qWarning()<<"raw audio format not supported by backend, cannot play audio.";
        format = info.nearestFormat(format);
    }
 
    audio = new QAudioOutput(format, this);
 
    connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(stateChanged(QAudio::State)));
 
    if( !buffer.open(QBuffer::ReadWrite) )
        qWarning() << "Couldnt open Buffer";
 
    qDebug() << "buffer.size()=" << buffer.size();
 
    audio->start(&buffer);
}

---

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?

Ok solved the problem by myself:

Code:

---

void MainWindow::try_with_ffmpeg()
{
    av_register_all();
 
    int             audioStream = -1;
    AVCodecContext  *codecContext;
    AVCodec         *codec;
    AVPacket        packet;
 
    av_open_input_file(&formatContext, WMV, NULL,0,NULL);
    av_find_stream_info(formatContext);
    av_dump_format(formatContext, 0, WMV,0);
 
    for( unsigned int i=0; i < formatContext->nb_streams; i++ )
    {
        if( formatContext->streams[i]->codec->codec_type == CODEC_TYPE_AUDIO )
        {
            audioStream = i;
            break;
        }
    }
    if( audioStream == -1 )
    {
        qWarning() << "Didnt find audio stream";
        return;
    }
 
    codecContext = formatContext->streams[audioStream]->codec;
 
    codec = avcodec_find_decoder(codecContext->codec_id);
    avcodec_open(codecContext,codec);
 
    med_buffer = (uint8_t*)malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
    buffer.open(QBuffer::WriteOnly);
 
    while( av_read_frame(formatContext,&packet) >= 0 )
    {
        qint64 written=0;
        if( packet.stream_index == audioStream )
        {
            qDebug() << "size= " << packet.size;
            while(packet.size > 0)
            {
                int len, data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
                //decode
                len = avcodec_decode_audio3(codecContext, (int16_t*)med_buffer, &data_size, &packet);
                if( len <= 0 )
                    qWarning() << "no data read to buffer";
                if( data_size > 0 )
                    written = buffer.write((const char*)med_buffer, data_size);
 
                packet.size -= len;
                packet.data += len;
 
                if( buffer.size() > 10000000 )
                {
                    qDebug() << "buffer.size()=" << buffer.size();
                    break;
                }
            }
 
        }
 
    }
 
    QAudioFormat format;
    format.setFrequency(codecContext->sample_rate);
    format.setChannels(2);
    format.setSampleSize(16);
    format.setCodec("audio/pcm");
    format.setByteOrder(QAudioFormat::LittleEndian);
    format.setSampleType(QAudioFormat::SignedInt);
 
    QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
 
    if (!info.isFormatSupported(format)) {
        qWarning()<<"raw audio format not supported by backend, cannot play audio.";
        format = info.nearestFormat(format);
    }
 
    audio = new QAudioOutput(format, this);
 
    connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(stateChanged(QAudio::State)));
 
    if( !buffer.open(QBuffer::ReadWrite) )
        qWarning() << "Couldnt open Buffer";
 
    qDebug() << "buffer.size()=" << buffer.size();
 
    audio->start(&buffer);
}

---

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!

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

Quote:

---

Originally Posted by Biberbaer

Ok solved the problem by myself:

Code:

---

void MainWindow::try_with_ffmpeg()
{
    av_register_all();
 
    int             audioStream = -1;
    AVCodecContext  *codecContext;
    AVCodec         *codec;
    AVPacket        packet;
 
    av_open_input_file(&formatContext, WMV, NULL,0,NULL);
    av_find_stream_info(formatContext);
    av_dump_format(formatContext, 0, WMV,0);
 
    for( unsigned int i=0; i < formatContext->nb_streams; i++ )
    {
        if( formatContext->streams[i]->codec->codec_type == CODEC_TYPE_AUDIO )
        {
            audioStream = i;
            break;
        }
    }
    if( audioStream == -1 )
    {
        qWarning() << "Didnt find audio stream";
        return;
    }
 
    codecContext = formatContext->streams[audioStream]->codec;
 
    codec = avcodec_find_decoder(codecContext->codec_id);
    avcodec_open(codecContext,codec);
 
    med_buffer = (uint8_t*)malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
    buffer.open(QBuffer::WriteOnly);
 
    while( av_read_frame(formatContext,&packet) >= 0 )
    {
        qint64 written=0;
        if( packet.stream_index == audioStream )
        {
            qDebug() << "size= " << packet.size;
            while(packet.size > 0)
            {
                int len, data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
                //decode
                len = avcodec_decode_audio3(codecContext, (int16_t*)med_buffer, &data_size, &packet);
                if( len <= 0 )
                    qWarning() << "no data read to buffer";
                if( data_size > 0 )
                    written = buffer.write((const char*)med_buffer, data_size);
 
                packet.size -= len;
                packet.data += len;
 
                if( buffer.size() > 10000000 )
                {
                    qDebug() << "buffer.size()=" << buffer.size();
                    break;
                }
            }
 
        }
 
    }
 
    QAudioFormat format;
    format.setFrequency(codecContext->sample_rate);
    format.setChannels(2);
    format.setSampleSize(16);
    format.setCodec("audio/pcm");
    format.setByteOrder(QAudioFormat::LittleEndian);
    format.setSampleType(QAudioFormat::SignedInt);
 
    QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
 
    if (!info.isFormatSupported(format)) {
        qWarning()<<"raw audio format not supported by backend, cannot play audio.";
        format = info.nearestFormat(format);
    }
 
    audio = new QAudioOutput(format, this);
 
    connect(audio,SIGNAL(stateChanged(QAudio::State)),SLOT(stateChanged(QAudio::State)));
 
    if( !buffer.open(QBuffer::ReadWrite) )
        qWarning() << "Couldnt open Buffer";
 
    qDebug() << "buffer.size()=" << buffer.size();
 
    audio->start(&buffer);
}

---

---

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