qcam: viewfinder: Avoid memory copy when conversion isn't needed

If the frame buffer format is identical to the display format, the
viewfinder still invokes the converter to perform what is essentially a
slow memcpy(). Make it possible to skip that operation by creating a
QImage referencing the buffer memory instead. A reference to the frame
buffer is kept internally, and released when the next buffer is queued,
pushing the current one out.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/qcam/viewfinder.h b/src/qcam/viewfinder.h
index 54c0fa9d..4d0622a8 100644
--- a/src/qcam/viewfinder.h
+++ b/src/qcam/viewfinder.h
@@ -36,6 +36,7 @@ public:
 
 	int setFormat(const libcamera::PixelFormat &format, const QSize &size);
 	void render(libcamera::FrameBuffer *buffer, MappedBuffer *map);
+	void stop();
 
 	QImage getCurrentImage();
 
@@ -52,6 +53,7 @@ private:
 	libcamera::PixelFormat format_;
 	QSize size_;
 
+	libcamera::FrameBuffer *buffer_;
 	QImage image_;
 	QMutex mutex_; /* Prevent concurrent access to image_ */
 };