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QtWS25 Call for Papers
  • 0 Votes
    13 Posts

    After a few months of searching for an definitive answer to this topic, I've reached the conclusion that my original assumption would be correct. This page describes how to determine the midpoint of a standard PCM audio signal:

    For example an 8-bit signed PCM signal has these ranges:

    Min: -128
    Max: 128
    Midpoint: 0

    As to why the signal I'm getting from my soundcard sits at -128 when there is no sound, I'm going to assume that this is related to a driver problem or could be that this particular piece of hardware does not follow the PCM standard.

    Converting to the logarithmic scale in my understanding is not related to this issue because you should be able to normalize the signal in time-domain even though eventually you will most likely need to convert it to the log scale if you are doing anything in the frequency domain (e.g. FFT).

    If anyone has any input, please feel free to add it.

  • 0 Votes
    6 Posts

    @sgaist Yep, I added a link to stack overflow. Concerning vlc I already looked at it but sadly there is some major drawbacks :

    -the documentation is poor or inexistant.
    -it does not allow fine tuning what you want at compile time as much as ffmpeg allows it (to reduce shared libs size).
    -it is partially based on ffmpeg anyway and I try to reduce as much as possible the amont of dependencies (for future compatibility and maintaining on my free time).

    Again thank you so much for the quick replies and the mailing list 🤩.

  • 1 Votes
    2 Posts


    You can get some information about that on this Wiki entry for Qt 5.5

  • 0 Votes
    6 Posts

    No problem :)

    Since you have it working now, please update the thread title prepending [solved] so other forum users may know that a solution has been found :)

    Also, when encountering answer(s) that helped you, please consider up-voting them so that other users may find them more easily.

    Happy coding !