Stopping and resuming video decoding

Since video decoding consumes both processing time and battery power, it can be practical to stop the decoding when the video being played is not visible in the device UI. For example, if the user is reading a message, viewing images, navigating the UI menus, or performing some other foreground task that fully covers the video being played in the background, decoding can be temporarily stopped. The video continues to play in the background, but the video stream is not processed in any way, saving processing time and battery power. When the video becomes visible again in the device UI, the MIDlet can resume decoding it, so that the user can see the video content.

To allow MIDlets to stop and resume video decoding during video playback, the Series 40 platform supports the VideoDecodeControl extension interface for the Mobile Media API (MMAPI). The VideoDecodeControl interface is intended for video player MIDlets that do not stop video decoding automatically when the MIDlet is moved to the background. Compared to the automatic stopping and starting of video decoding, the VideoDecodeControl interface allows for finer control over when video decoding is used.

Depending on the video content and the Player implementation, stopping and resuming video decoding can cause short-term image distortion visible to the user. To avoid this, program the MIDlet to stop video decoding only when the benefits of saved processing time and battery power outweigh the drawbacks of a poor user experience caused by image distortion. For example, stopping video decoding can be practical when the user causes an application or a UI element to fully cover the video area, but not when the video area becomes only partially covered, leaving a portion of the video visible.

For more information about creating a video Player, see section Playing video.

// create a VideoDecodeControl for the Player instance
VideoDecodeControl vdc = (VideoDecodeControl)player.getControl("VideoDecodeControl");

// stop video decoding while the video is still playing
if (vdc != null)
    vdc.setDecodeStatus(VideoDecodeControl.DECODE_STATUS_OFF);

vdc.setDecodeStatus(VideoDecodeControl.DECODE_STATUS_FULL);

int status = vdc.getDecodeStatus();