Zero shutter lag in Android camera

Question

In normal shutter lag,sensor driver give the caputured image buffer to v4l2 layer and here jpeg(hardware) header adds some extra data(exif info and thumbnail) and this layer give the image buffer to preview heap(In HAL layer) for further processing. but what is the process of taking picture in case of zero shutter lag.Is this same as normal shutter lag? How to reduce the time between take picture call and image processing. if not than explain .

Answer 1

To achieve zero shutter lag, the camera driver must maintain a small circular buffer pool containing full resolution frames. Images are captured at sensor rate and are sent to preview and to the circular buffer pool (either as raw Bayer or as processed/semi-processed YUV). When the use presses the shutter, the newest buffer in the circular pool is extracted, processed and compressed as JPEG. On older mobile phone cameras, the sensor is not able to capture full resolution frames at a high enough frame rate, and therefore ZSL cannot be implemented.