# SDL_SetAudioStreamInputChannelMap

Set the current input channel map of an audio stream.

## Header File

Defined in [<SDL3/SDL_audio.h>](https://github.com/libsdl-org/SDL/blob/main/include/SDL3/SDL_audio.h)

## Syntax

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

## Function Parameters

|                                      |            |                                                   |
| ------------------------------------ | ---------- | ------------------------------------------------- |
| [SDL_AudioStream](SDL_AudioStream) * | **stream** | the [SDL_AudioStream](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](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](CategoryAudio#channel-layouts).

The input channel map reorders data that is added to a stream via
[SDL_PutAudioStreamData](SDL_PutAudioStreamData). Future calls to
[SDL_PutAudioStreamData](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.

Unlike attempting to change the stream's format, the input channel map on a
stream bound to a recording device is permitted to change at any time; any
data added to the stream from the device after this call will have the new
mapping, but previously-added data will still have the prior mapping.

## 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 different thread at the same
time, though!

## Version

This function is available since SDL 3.2.0.

## See Also

- [SDL_SetAudioStreamOutputChannelMap](SDL_SetAudioStreamOutputChannelMap)

----
[CategoryAPI](CategoryAPI), [CategoryAPIFunction](CategoryAPIFunction), [CategoryAudio](CategoryAudio)

