camera_start_burst()

Start to capture photos in rapid succession.

Synopsis:

#include <camera/camera_api.h>
 
camera_error_t camera_start_burst(camera_handle_t handle,                 
                                  void(*shutter_callback)(camera_handle_t, void *),                 
                                  void(*raw_callback)(camera_handle_t, camera_buffer_t *, void *),                 
                                  void(*postview_callback)(camera_handle_t, camera_buffer_t *, void *),                 
                                  void(*image_callback)(camera_handle_t, camera_buffer_t *, void *),                 
                                  void *arg)

Since:

BlackBerry 10.0.0

Arguments:

handle

The handle returned by a call to the camera_open() function.

shutter_callback
A function pointer to a function with the following signature:
 void function_name( camera_handle_t,
                     void* );
The function is a callback that is invoked when the shutter activates. Typically, the callback function plays a shutter sound. You can use NULL if no function needs to be called. For information about the callback arguments, see About callback mode.
raw_callback

Use NULL. Reserved for future use.

postview_callback
A function pointer to a function with the following signature:
 void function_name( camera_handle_t,
                     camera_buffer_t*,
                     void* );
The function is a callback that is invoked when a post-view (review) image is available. This callback is used to provide a preview-sized copy of the photo. Typically, the preview-sized photo is used to provide visual feedback before the final image is available. You can use NULL if no function needs to be called. For information about the callback arguments, see About callback mode.
image_callback
A function pointer to a function with the following signature:
 void function_name( camera_handle_t,
                     camera_buffer_t*,
                     void* );
The function is a callback that is invoked when a full-resolution image is available. You can use NULL if no function needs to be called. For information about the callback arguments, see About callback mode.
arg

The argument passed to all callback functions, which is the last argument in the callback functions.

Library:

libcamapi (For the qcc command, use the -l camapi option to link against this library)

Description:

Before you take photos, ensure that you have configured the viewfinder, set the output properties for the photo, and started the viewfinder. This function can only be called if the CAMERA_FEATURE_CONTINUOUSBURST feature is available. You can determine whether this feature is available by calling the camera_can_feature() function.

The viewfinder must be started in CAMERA_VFMODE_CONTINUOUS_BURST mode. Burst capture is also possible using the deprecated photo viewfinder with CAMERA_IMGPROP_BURSTMODE set to 1. For more information about viewfinder modes, see Viewfinder modes.

This function does not block. To terminate a continuous burst capture, call the camera_stop_burst() function.

Unlike the camera_take_burst() function, there is no upper limit to the number of pictures you can take. Buffers are only valid for the duration of the callback to prevent memory exhaustion. To prevent memory exhaustion, you can:
  • Maintain a circular buffer in order to implement negative-shutter lag.
  • Maintain a growing heap of buffers after capture begins in order to select your favorite photo — after the fact.
  • Only capture images where certain criteria has been met. For example, capture images that contain only smiles or when three faces are seen in the photo.

Burst runs at the frame rate specified by calling camera_set_photo_property() to set CAMERA_IMGPROP_FRAMERATE. Use the camera_start_burst() function when image-capture latency is a concern or when your application cannot tolerate brief disruptions to the viewfinder. Brief disruptions can occur when using the camera_take_photo() function.

You should make copies of the frames as they arrive and exit the callback as quickly as possible. You should avoid saving the files within your image_callback function because writing to disk may take more time that is available before the next frame arrives. Buffers are only valid until your callback function returns. Memory that was valid before a callback begins executing may be unmapped from your process when the callback completes. Attempts to access memory buffers after the end of a callback function may result in memory access errors.

The Camera library does not automatically play audible shutter sounds when a picture is taken or a video is recorded. Camera applications must supply their own sound when a photo is captured or a video recording begins and ends. While you can choose to not have a shutter sound when taking a picture — you are responsible to ensure that the application adheres to the local laws of the regions in which you wish to distribute the application.

For example, it is illegal to mute or modify the shutter sound of a camera application in Japan and Korea. Ensure that you comply with the laws and regulations for the countries in which you distribute your application. For more information, see the BlackBerry World Vetting Criteria at https://appworld.blackberry.com/isvportal/home.do.

Since burst mode captures images in rapid succession, you can choose an appropriate moment to play the shutter sound rather than play the shutter sound repeatedly.

It is important that your application follows the guidelines for resource management outlined in Camera resource management. If you do not observe these guidelines, your application is at risk of crashing due to memory access errors when resource arbitration is performed by the operating system.

Returns:

CAMERA_EOK when the function successfully completes, otherwise another camera_error_t value that provides the reason that the callfailed.

Last modified: 2014-09-30



Got questions about leaving a comment? Get answers from our Disqus FAQ.

comments powered by Disqus