It seems that when the user selects "Disabled" for the disc noise volume (Menu->Disc >Disc drive noise->Disabled), Arculator internally sets the disc noise gain to a certain constant, DISC_NOISE_DISABLED (with the value of +9999). With the old OpenAL code, Arculator checked for this special constant and, if it was there, returned without giving any sound data to OpenAL. The code to do this was inadvertently dropped when the sound system changed from OpenAL to SDL, meaning that when the disc noise is set to "Disabled", Arculator interprets the gain level as +9999, amplifying and distorting the drive noise to the point where it's just white noise at maximum volume, instead of playing silence as it should.
Although this PR fixes the issue in a manner that's closest to the way it worked under OpenAL, I'm a little uncomfortable with this fix because it means that disc_noise_gain is used in two different routines for different purposes. sound_givebufferdd appears to be intended for a "canonical" disc noise sound, whereas sound_givebuffer is what actually mixes the disc noise buffer into the output stream and attenuates the volume using the disc_noise_gain variable. An alternative method of doing this patch would be to keep sound_givebufferdd providing a "canonical" drive sound while modifying sound_givebuffer to avoid mixing in the disc noise sound.
I've tested both methods and they both seem to work fine, but I chose to submit this method as it's the most similar to the method used in the code previously. I am happy to force-push the alternate method to this PR if wanted.
It seems that when the user selects "Disabled" for the disc noise volume (Menu->Disc >Disc drive noise->Disabled), Arculator internally sets the disc noise gain to a certain constant,
DISC_NOISE_DISABLED(with the value of +9999). With the old OpenAL code, Arculator checked for this special constant and, if it was there, returned without giving any sound data to OpenAL. The code to do this was inadvertently dropped when the sound system changed from OpenAL to SDL, meaning that when the disc noise is set to "Disabled", Arculator interprets the gain level as +9999, amplifying and distorting the drive noise to the point where it's just white noise at maximum volume, instead of playing silence as it should.Although this PR fixes the issue in a manner that's closest to the way it worked under OpenAL, I'm a little uncomfortable with this fix because it means that
disc_noise_gainis used in two different routines for different purposes.sound_givebufferddappears to be intended for a "canonical" disc noise sound, whereassound_givebufferis what actually mixes the disc noise buffer into the output stream and attenuates the volume using thedisc_noise_gainvariable. An alternative method of doing this patch would be to keepsound_givebufferddproviding a "canonical" drive sound while modifyingsound_givebufferto avoid mixing in the disc noise sound.I've tested both methods and they both seem to work fine, but I chose to submit this method as it's the most similar to the method used in the code previously. I am happy to force-push the alternate method to this PR if wanted.
Fixes #38.