(This is the documentation for SDL3, which is the current stable version. SDL2 was the previous version!)

SDL_SetAudioStreamInputChannelMap

Set the current input channel map of an audio stream.

Header File

Syntax

bool SDL_SetAudioStreamInputChannelMap(SDL_AudioStream *stream, const int *chmap, int count);

Function Parameters

SDL_AudioStream *	stream	the SDL_AudioStream to change.
const int *	chmap	the new channel map, NULL to reset to default.
int	count	The number of channels in the map.

Return Value

(bool) Returns true on success or false on failure; call SDL_GetError() for more information.

Remarks

Channel maps are optional; most things do not need them, instead passing data in the order that SDL expects.

The input channel map reorders data that is added to a stream via SDL_PutAudioStreamData. Future calls to SDL_PutAudioStreamData must provide data in the new channel order.

Each item in the array represents an input channel, and its value is the channel that it should be remapped to. To reverse a stereo signal's left and right values, you'd have an array of { 1, 0 }. It is legal to remap multiple channels to the same thing, so { 1, 1 } would duplicate the right channel to both channels of a stereo signal. An element in the channel map set to -1 instead of a valid channel will mute that channel, setting it to a silence value.

You cannot change the number of channels through a channel map, just reorder/mute them.

Data that was previously queued in the stream will still be operated on in the order that was current when it was added, which is to say you can put the end of a sound file in one order to a stream, change orders for the next sound file, and start putting that new data while the previous sound file is still queued, and everything will still play back correctly.

Audio streams default to no remapping applied. Passing a NULL channel map is legal, and turns off remapping.

SDL will copy the channel map; the caller does not have to save this array after this call.

If count is not equal to the current number of channels in the audio stream's format, this will fail. This is a safety measure to make sure a race condition hasn't changed the format while this call is setting the channel map.

Thread Safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running. Don't change the stream's format to have a different number of channels from a a different thread at the same time, though!

Version

This function is available since SDL 3.1.3.