1# preview_output.h 2 3 4## Overview 5 6The **preview_output.h** file declares the preview output concepts. 7 8**Library**: libohcamera.so 9 10**System capability**: SystemCapability.Multimedia.Camera.Core 11 12**Since**: 11 13 14**Related module**: [OH_Camera](_o_h___camera.md) 15 16 17## Summary 18 19 20### Structs 21 22| Name| Description| 23| -------- | -------- | 24| [PreviewOutput_Callbacks](_preview_output___callbacks.md) | Defines the callbacks used for preview output.| 25 26 27### Types 28 29| Name| Description| 30| -------- | -------- | 31| [Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) | Defines the preview output object.| 32| (\*[OH_PreviewOutput_OnFrameStart](_o_h___camera.md#oh_previewoutput_onframestart)) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput) | Defines the pointer to the callback defined in the [PreviewOutput_Callbacks](_preview_output___callbacks.md) struct and used to report preview output frame start events.| 33| (\*[OH_PreviewOutput_OnFrameEnd](_o_h___camera.md#oh_previewoutput_onframeend)) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput, int32_t frameCount) | Defines the pointer to the callback defined in the [PreviewOutput_Callbacks](_preview_output___callbacks.md) struct and used to report preview output frame end events.| 34| (\*[OH_PreviewOutput_OnError](_o_h___camera.md#oh_previewoutput_onerror)) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput, [Camera_ErrorCode](_o_h___camera.md#camera_errorcode) errorCode) | Defines the pointer to the callback defined in the [PreviewOutput_Callbacks](_preview_output___callbacks.md) struct and used to report preview output errors.| 35| [PreviewOutput_Callbacks](_o_h___camera.md#previewoutput_callbacks) | Defines the callbacks used for preview output.| 36 37 38### Functions 39 40| Name| Description| 41| -------- | -------- | 42| [OH_PreviewOutput_RegisterCallback](_o_h___camera.md#oh_previewoutput_registercallback) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput, [PreviewOutput_Callbacks](_preview_output___callbacks.md) \*callback) | Registers a callback to listen for preview output events.| 43| [OH_PreviewOutput_UnregisterCallback](_o_h___camera.md#oh_previewoutput_unregistercallback) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput, [PreviewOutput_Callbacks](_preview_output___callbacks.md) \*callback) | Unregisters the callback used to listen for preview output events.| 44| [OH_PreviewOutput_Start](_o_h___camera.md#oh_previewoutput_start) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput) | Starts preview output.| 45| [OH_PreviewOutput_Stop](_o_h___camera.md#oh_previewoutput_stop) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput) | Stops preview output.| 46| [OH_PreviewOutput_Release](_o_h___camera.md#oh_previewoutput_release) ([Camera_PreviewOutput](_o_h___camera.md#camera_previewoutput) \*previewOutput) | Releases a **PreviewOutput** instance.| 47