如何使用TagLib-C ++从MP3文件读取XingHeaders，VBRIHeaders和sampleCount

Question

Is there a way to determine if an audio file has a variable bitrate, and extract the sampleCount() through the LibTag? I need to find out 'cause the Qt QMediaPlayer class incorrectly calculates audio files duration with variable bitrate, and the only way to correct is discover if the audio has a variable bit rate and divide the length for sampleCount() duration.

Since the documentation TagLib is a bit confusing, I managed to create just the fileref

void MainWindow::playerOnMediaStatusChanged(QMediaPlayer::MediaStatus status)
{
if (status == QMediaPlayer::BufferedMedia) {     
QString mediafile = playlist->currentMedia().canonicalUrl().toString();
TagLib::FileRef fr(reinterpret_cast<constwchar_t*>(mediafile.utf16()),true);
        //…
    }
}

But I don't know how do for discover if the audio has a variable bit rate and its sampleCount()

Yes, I know there is this topic , but is related to Sharp language

Can you help me?

Thanks in advance

Answer 1

You need to be working with a TagLib::MPEG::File to be able to access the XingHeader . Here's an example:

static void printXingHeader(const char *fileName)
{
    TagLib::FileRef ref(fileName);
    TagLib::MPEG::File *file = dynamic_cast<TagLib::MPEG::File *>(ref.file());

    if(!file)
        return;

    TagLib::MPEG::Properties *properties = file->audioProperties();
    const TagLib::MPEG::XingHeader *xingHeader = properties->xingHeader();

    if(!xingHeader)
        return;

    std::cout << "total frames: " << xingHeader->totalFrames()
              << " total size: " << xingHeader->totalSize()
              << std::endl;

}