When I try to make UniPCemu record audio using it's Sound Blaster emulation, which I've modified a little bit to allow real-time recording as well as inputting a test signal(1Hz sine wave) for testing, somehow the audio ends up being a lot of noise instead of the intended wave. Is it correct, that the input signal using the Sound Blaster 2.0 is just a simple unsigned 8-bit signal? (0=-5V, 128=0V, 255=+5V)

It currently generates a 16-bit PCM stream for recording, like the actual recording in the OS does(SDL2 recording input).

1						#ifdef RECORD_TESTWAVE
2						sample = (sword)(sinf(2.0f*PI*1.0f*recordtime)*(SHRT_MAX/2.0)); //Use a test wave instead!
3						recordtime += (1.0f/SOUNDBLASTER.frequency); //Tick time by one sample!
4						recordtime = fmodf(recordtime,1.0f); //Wrap around a second!
5						SOUNDBLASTER.recordedsample = ((signed2unsigned16(sample)>>8)^0x80); //Test sample to use!
6						#else
7						SOUNDBLASTER.recordedsample = (byte)(((word)getRecordedSampleL8u()+(word)getRecordedSampleR8u())*0.5f); //Update recording samples in real-time, mono!
8						#endif

The signed2unsigned and unsigned2signed function just convert between (un)signed variants of the same variable by putting it in a union and reading the (un)signed version from the other variable. That way, signed vs unsigned conversions are easily handled without chance of data being modified by compiler logic in ways that are unintended(assuming signed vs unsigned have the same size). So unsigned 32768 is signed -32768 when converted that way.

I'm using the record.exe from the Sound Blaster 1.5 driver disks at http://www.vogonsdrivers.com/index.php?catid= … menustate=42,35

Resulting recording of the Sound Blaster recording a 1Hz wave:

Anyone can see what's going wrong in the emulation?

Sound Blaster source code(RECORD_TESTWAVE makes it generate a 1Hz test wave on the recording input instead of the actual recording from the SDL input):
https://bitbucket.org/superfury/unipcemu/src/ … ter.c?at=master