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# SetShapePcmLoopStartOrWritePointer

> SetShapePcmLoopStartOrWritePointer

# SetShapePcmLoopStartOrWritePointer

Sets the loop start for linear buffers or a write pointer for circular buffers.

## Syntax

```cpp theme={null}
HRESULT SetShapePcmLoopStartOrWritePointer(  
         SHAPE_PCM_CONTEXT* context,  
         UINT32 loopStartOrWritePointerInSamples  
)  
```

### Parameters

*context*   \_Inout\_\
Type: [SHAPE\_PCM\_CONTEXT\*](/reference/audio/shapepcmcontext/structs/shape_pcm_context)

Pointer to a [SHAPE\_PCM\_CONTEXT](/reference/audio/shapepcmcontext/structs/shape_pcm_context) structure.

*loopStartOrWritePointerInSamples*   \
Type: UINT32

Specifies the loop start or a write pointer.

### Return value

Type: HRESULT

HRESULT success or error code.

## Remarks

| Function                    | Description                                                                                                                                                                                                                                                                                                                                                                                       |
| --------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Non-looping linear PCM      | Start the voice using the `SHAPE_SRC_COMMAND_TYPE_START` constant for the Sample Rate Convertor (SRC). Let the voice play to the end, or optionally stop it short of the end using the `SHAPE_SRC_COMMAND_TYPE_STOP_IMMEDIATE` constant. For more information, see the [SHAPE\_SRC\_COMMAND\_TYPE](/reference/audio/shapesrccontext/enums/shape_src_command_type) enumeration.                    |
| Infinite looping linear PCM | Set the Pulse Code Modulation (PCM) context loop count *loopCount* to the `SHAPE_PCM_INFINITE_LOOP_COUNT` constant. Start the voice using `SHAPE_SRC_COMMAND_TYPE_START` for the SRC. Let the voice play until you want to stop, either at the end of a loop using `SHAPE_SRC_COMMAND_TYPE_STOP_END` and let the voice play out, or immediately by using `SHAPE_SRC_COMMAND_TYPE_STOP_IMMEDIATE`. |
| Finite looping linear PCM   | Set the PCM context loop count *loopCount* to \[0, 254]. Start the voice using `SHAPE_SRC_COMMAND_TYPE_START` for the SRC. Let the voice play to the end, or optionally stop it at the end of a loop using `SHAPE_SRC_COMMAND_TYPE_STOP_END` and let the voice play out, or stop it immediately by using `SHAPE_SRC_COMMAND_TYPE_STOP_IMMEDIATE`.                                                 |
| Circular PCM                | Start the voice using `SHAPE_SRC_COMMAND_TYPE_START` for the SRC. Keep streaming data, updating the PCM context write pointer, until you want to stop. Use `SHAPE_SRC_COMMAND_TYPE_STOP_END` to let the SRC play to the current PCM write pointer `loopStartWritePointer`, or `SHAPE_SRC_COMMAND_TYPE_STOP_IMMEDIATE`to stop it immediately.                                                      |

## Requirements

**Header:** shapepcmcontext.h

**Supported platforms:** XBOX One family consoles and XBOX Series consoles

## See also

[Overview of ACP](/build/console-features/audio/overviews/acp-overview)\
[Overview of Shape](/build/console-features/audio/overviews/shape-overview)\
[shapepcmcontext](/reference/audio/shapepcmcontext/shapepcmcontext_members)


## Related topics

- [ShapePcmContext](/reference/audio/shapepcmcontext/shapepcmcontext_members.md)
- [GetShapePcmLoopStartOrWritePointer](/reference/audio/shapepcmcontext/functions/getshapepcmloopstartorwritepointer.md)
- [SetShapePcmLoopCount](/reference/audio/shapepcmcontext/functions/setshapepcmloopcount.md)
- [SetShapePcmLoopEnd](/reference/audio/shapepcmcontext/functions/setshapepcmloopend.md)
- [SetShapePcmFormat](/reference/audio/shapepcmcontext/functions/setshapepcmformat.md)