[GZDoom] A playback error with stereo samples in MOD music

[pablo tescobar]

I found a MOD music playback bug in GZdoom: if there is a stereo sound sample in a MOD music file (IT, S3M, XM...) and it has either a bidi (ping pong) or On loop setting, then the right channel of that sample is played in a weird offset.

 

Here's how the sample looks like in OpenMPT:

 

I recorded ingame with OBS and this is the audio visualized in Vegas, where the highlighted area is the first map:

 

I tested turning loop setting to Off in OpenMPT, and it's played perfectly normal ingame.

ITstereoexample.rar

[Gez]

GZDoom uses foo_DUMB as its module replayer. So the problem is likely to come from it. The version used in GZDoom hasn't been updated in a while, so perhaps it's been fixed since. Does your track play correctly in foobar2000?

[pablo tescobar]

6 minutes ago, Gez said:

GZDoom uses foo_DUMB as its module replayer. So the problem is likely to come from it. The version used in GZDoom hasn't been updated in a while, so perhaps it's been fixed since. Does your track play correctly in foobar2000?

Yes.

[pablo tescobar]

Bump:

I tested removing the soundbits after the end loop point in OpenMPT:

 

Ingame, the problem is sort of fixed: the right channel is now played some milliseconds after the left channel begins, creating the surround sound effect.

 

My verdict is that is based on the amount of extra sound bits after the end loop point as seen in OpenMPT. It's probably why in the first post the right channel sounds so off.