MIX_GroupMixCallback(3type)

🎀 MIX_GroupMixCallback 🎀

okay bestie, welcome to the tea on MIX_GroupMixCallback — it's a datatype from SDL_mixer3 (yes, the DATATYPES section, she's that girl) and she's literally the callback that fires the second a MIX_Group is done mixing. 💖

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✨ NAME ✨

MIX_GroupMixCallback — a callback that fires when a MIX_Group has completed mixing. that's it, that's the function. periodt. 💅

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✨ SYNOPSIS ✨

#include <SDL3_mixer/SDL_mixer.h>

typedef void (SDLCALL *MIX_GroupMixCallback)(void *userdata, MIX_Group *group, const SDL_AudioSpec *spec, float *pcm, int samples);

look at her 😭 so iconic. keep it exact, no cap, every type and qualifier stays where it is.

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✨ DESCRIPTION ✨

so here's the vibe: this callback fires when a mixing group has finished mixing. all the tracks in the group have already been mixed down into a single buffer, and they're sitting there ready to get mixed into all the other groups for the final mix output. 🎚️✨

huge thing to know: the audio data that comes through here is not const data. nope. the app is 100% allowed to change it however it wants, and those changes will propagate through the mixing pipeline. you're not a spectator, bestie, you're a co-author. 💅

an audiospec gets handed to you too. different groups might be in different formats (chaotic, i know), and an app needs to be able to handle that. but here's the reassuring part: SDL_mixer always does its mixing work in 32-bit float samples, even if the inputs or the final output are not floating point. so basically spec->format will always be SDL_AUDIO_F32, and pcm is hardcoded to be a float pointer. no surprises, we love consistency. 🫶

and samples? that's the number of float values pointed to by pcm — samples, not sample frames! ⚠️ say it with me now. also there are no promises about how many samples you'll get per-callback, and that number can vary wildly from call to call depending on many factors. it's giving chaos but make it audio. 💀

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✨ FUNCTION PARAMETERS ✨

• userdata — an opaque pointer that the app provides for its own personal use. it's yours, do whatever, we're not looking. 🙈
• group — the group that's being mixed. the main character of this particular call. 👑
• spec — the format of the data sitting in pcm.
• pcm — the raw PCM data, in float32 format. 🍓
• samples — the number of float values pointed to by pcm. (yes, values. not frames. we covered this. 😭)

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✨ AVAILABILITY ✨

this datatype has been available since SDL_mixer 3.0.0. she's not new new, she's established. 💜

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✨ SEE ALSO ✨

• MIX_SetGroupPostMixCallback(3) — go read her next, she's literally the sibling. 🌸

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kay that's the whole page bestie, hope it ate 🎀✨

signing off with love from the SDL_mixer girlies — this one's from version SDL_mixer 3.2.4, page MIX_GroupMixCallback(3type). mwah 💋