I was wondering if it is possible to capture a copy of the audio output in Qt so I can process it. Here they said it's possible to monitor the playback, but I think it's only possible if you use a self made music player, which I don't want. I want to capture the signal from no matter where it is player (youtube, spotify, facebook, etc.). Is there a way to analyze this data with Qt? Is it possible to set my output of my soundcard as a QMediaSource?
Thank you in advance.
In general, no, that isn't possible, simply because your process (and therefore the Qt library that is loaded into your process) does not have access to that information. (I believe this lack of access is deliberate; since if it did have access like that, there might be security and/or privacy implications, i.e. app A could use it to spy on the audio output of app B, etc)
There may be an OS-specific mechanism that you can use; for example, if you are running your program under MacOS/X, you can install the SoundFlower audio driver that can function as a loopback device, allowing programs to read audio from its "audio input" that was previously routed to its "audio output". But without that kind of external support, it's not currently possible to record the computer's audio output via Qt.