audio decoding using DirectShow not supported, switching to Windows Media Foundation breaks media file compatibility, QAudioDecoder not signalling error

Hey everyone,
I'm trying to decode audio using the QAudioDecoder class. It works fine on Linux, but under Windows it will not decode my files (ogg audio file, codecs are installed). The QMediaPlayer object plays my files though when I let Qt choose the decoder freely.

I've tried to set the media backend to Windows Media Foundation by setting it as preferred in the environment variables. Turns out that the WMF backend is very limited on the audio side in terms of available codecs. Now the QMediaPlayer signals a FormatError, but QAudioDecoder does not emit any signals (not even an error signal) on windows. The wiki says, that audio decoding is only supported using the windows media foundation backend.
I need QAudioDecoder in order to plot a waveform of the loaded audio.

Therefore I request adding support for using DirectShow for audio decoding and hope you can fix the bug that leads to QAudioDecoder NOT signalling an error.

The tested audiofiles use the Vorbis codec inside an Ogg container, have a 192 kB/s bitrate with 32-bit (probably float) sample size with 48khz sampling rate, are mono-channel and are usually 1-10 seconds long.

Here is the code.
https://github.com/KaitoCross/TacoTranscribe/blob/winfixes/audiograph.cpp
Important for this case are lines 21-23, 44-45, 116-120.