(This function is part of SDL_mixer, a separate library from SDL.)

MIX_PostMixCallback

A callback that fires when all mixing has completed.

Header File

Syntax

typedef void (SDLCALL *MIX_PostMixCallback)(void *userdata, MIX_Mixer *mixer, const SDL_AudioSpec *spec, float *pcm, int samples);

Function Parameters

userdata	an opaque pointer provided by the app for its personal use.
mixer	the mixer that is generating audio.
spec	the format of the data in `pcm`.
pcm	the raw PCM data in float32 format.
samples	the number of float values pointed to by `pcm`.

Remarks

This callback is fired when the mixer has completed all its work. If this mixer was created with MIX_CreateMixerDevice(), the data provided by this callback is what is being sent to the audio hardware, minus last conversions for format requirements. If this mixer was created with MIX_CreateMixer(), this is what is being output from MIX_Generate(), after final conversions.

The audio data passed through here is not const data; the app is permitted to change it in any way it likes, and those changes will replace the final mixer pipeline output.

An audiospec is provided. SDL_mixer always does its mixing work in 32-bit float samples, even if the inputs or final output are not floating point. As such, spec->format will always be SDL_AUDIO_F32 and pcm hardcoded to be a float pointer.

samples is the number of float values pointed to by pcm: samples, not sample frames! There are no promises how many samples will be provided per-callback, and this number can vary wildly from call to call, depending on many factors.

Version

This datatype is available since SDL_mixer 3.0.0.