Measure the level and record the sound entering the audio output?

Question

Audio

Is it possible in Windows to measure the level and record the audio stream (say, to a file) that comes from a single process (from its program) to an audio output device? After all (seemingly) there is the possibility of adjusting the volume for a single application.
An alternative question, maybe someone knows: how to do the same using the mediastreamer2 media engine (measuring the audio signal level, recording audio to a file)? In fact, sound playback in my program is carried out with the help of it, and it is desirable to work with audio data directly using engine functions, rather than doing it indirectly. The problem is that I did not find the documentation for the engine, and I did not see the required functionality in the source codes.

Answer 1

I used to do something like this (on a 486 computer in Windows 95): I
opened the Sound Recorder program (in it I chose the recording format WAVE PCM mono 8 bit 8 kHz).
I pressed the "record" button, saved it to disk, and then opened the resulting file using a simple program on turbo pascal, and read 1 byte from the file. Based on the last 255 (possibly less) bytes, I calculated the amplitude of the signal (the difference between the maximum and minimum values ​​of the bytes of this interval). This was actually the same signal level.
Such low accuracy was quite enough for me to fine-tune the level of the line-in signal (I was digitizing audio recordings at that time).
At the same time, I also managed to adjust the level so that the amplitude was as high as possible, and at the same time there was no off-scale input signal level ...
... oh, where are my seventeen years