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Confused by Allegro 5's sound routines
Member #16,038
August 2015

Hi Everyone,

This is my first post here but I've been using Allegro5 for a while and usually do okay, but today I have I dilemma.

I'm porting an old project I did in allegro 4 which had radial sound effects, for simplicity there was a location (512,384) where a looped sound effect 'was', and there was a sprite who moved around the screen. The volume of the effect was based on his distance to the effect:

1dX = spriteX - 512; 2dY = spriteY - 384; 3distance = sqrt((dX * dX) + (dY * dY)); 4volume = 255 - distance; 5if(volume < 0) 6{ 7volume = 0; 8}

Then if I remember correctly I simply set the volume of the looping sample to this volume.

The problem is I can't workout how to set the volume of an already playing sample in Allegro 5. Please can someone advise me as to how I can make this work, I thought it might be to do with Mixers ???, but I couldn't work it out from the docs.

Thank you,


l j
Member #10,584
January 2009

Use sample instances instead, you can create them from samples. It allows you to play samples but also modify them in real-time. You don't have to manually set up a mixer and voice to make them work.

To change the volume you'd have to use al_set_sample_instance_gain which as far as I know should be between 0.0 and 1.0 to avoid hard clipping.

Member #16,038
August 2015

Thanks Taron

That's good to know.


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