Zero-duration Tweens are not actually instantaneous on buffer sizes > 1

[DaforLynx]

I was trying to set track volume to a low value while simultaneously playing a new source from that track. I used a Tween with duration of 0.0. However, that resulted in a "pop" as the sound played for a split second before the volume leapt down. When I set the buffer size to 1, this doesn't happen. This leads me to believe Tweens only take effect on the next buffer frame, instead of starting on the current one. I don't know what the solution is, as I can see why Tweens might not be able to take effect instantaneously. Perhaps there should be a way to play() a source specifically on the next buffer frame.

[tesselode]

Changing volume instantaneously will result in an audible click because you're creating a discontinuity in the audio waveform. That's why Tween::default has a duration of 10ms - it's fast enough to sound instant to a human, but slow enough to not cause an audible click.

[DaforLynx]

@tesselode so is there a way to set the volume of a track at the same time as a sound begins playing, therefore not resulting in a click as the volume is already set?

[DaforLynx]

To be clear, the click is expected in the case I set the volume with a zero-duration Tween during playback. But I'm setting the volume at the same time playback starts here.

[tesselode]

@DaforLynx my apologies, I didn't read the issue closely enough.

Currently, parameters like volume and panning are updated once per buffer, and the value for each sample is interpolated from the previous and current value. So yes, tweens will have a minimum duration of 1 buffer length.

Are you creating the track just to play this sound? If so, I'd just set the initial volume in the track builder. Otherwise, can you get away with just setting the track volume earlier? Or setting the volume of the individual sound instead of the whole track?

[DaforLynx]

The only thing I can think of is delaying the playback of the sound by one buffer length, but that seems inexact, as I'm using the Clock to handle delays.

The context is that I'm playing back positional sfx with additional volume changes (in addition to the standard "listener position" 3D audio) based on the player character's position. So the very frame a sfx is emitted, the volume calculation is done and it should emit with the adjustment. I can't set source volume since I want the sound volume to update every frame. Or, actually...maybe I can.

[tesselode]

Older versions of Kira had problems when setting volumes every frame, but recent ones should be fine.

[DaforLynx]

Ok, I have been banging my head against this wall for a bit. I found that, no, it's not simply the volume tween that results in the popping. I can set the SoundData's volume before playing it and it'll still pop.

I think it's quite likely that it's a result of setting the emitter position with a Tween. To recap:

• I want a sound to occur at a location.
• I have to give it to a SpatialTrack and set that SpatialTrack position to its location.
• If I want to do that after the Track has been created, it can only be done with spatial_track_handle.set_position() , which requires a Tween.
• Result: the sound and track-position-setting occur simultaneously, but the position is set one buffer frame after the sound begins.

Am I incorrect that this is unavoidable?

[tesselode]

That sounds believable. Is there a reason why you can't create the spatial track with the correct position in the first place?

[DaforLynx]

Mainly I'm concerned with performance for potentially creating and dropping dozens of new channel objects per second, but I guess there's no harm in trying.

[DaforLynx]

Ok, that worked! No more popping. It didn't slow down my computer when rapidly emitting, though I've not ever had problems with that in the past.

[DaforLynx]

Some profiling in heavy situations reveals the load produced by many add_spacial_sub_track()s per second isn't entirely trivial, though it's not debilitating either. It'll be worth investigating a different solution for our game.