Method and system for encoding video with overlay

A video encoding system comprising:

• an image receiver arranged to receive an image sequence comprising a first input image frame and a second input image frame,
• an overlay receiver arranged to receive an overlay to be applied to the image sequence, the overlay comprising a picture element and spatial coordinates for positioning the picture element in the first and second input image frames,
• an overlay applicator arranged to add the picture element to the first and second input image frames in accordance with the spatial coordinates, thereby generating an overlaid image sequence comprising a first generated image frame and a second generated image frame,
• an encoder arranged to encode a video stream containing output image frames without overlay and corresponding output image frames with overlay, wherein:
• the first input image frame is encoded as an intra-frame to form a first output image frame,
• the second input image frame is encoded as an inter-frame with reference to the first output image frame to form a second output image frame,
• the first generated image frame is encoded as an inter-frame with reference to the first output image frame to form a first overlaid output image frame,
• the second generated image frame is encoded as an inter-frame to form a second overlaid output image frame, wherein a first part of the second generated image frame is encoded with reference to the first overlaid output image frame, and a second part of the second generated image frame is encoded with reference to the second output image frame.

A camera including an encoding system comprising:

• an image receiver arranged to receive an image sequence comprising a first input image frame and a second input image frame,
• an overlay receiver arranged to receive an overlay to be applied to the image sequence, the overlay comprising a picture element and spatial coordinates for positioning the picture element in the first and second input image frames,
• an overlay applicator arranged to add the picture element to the first and second input image frames in accordance with the spatial coordinates, thereby generating an overlaid image sequence comprising a first generated image frame and a second generated image frame,
• an encoder arranged to encode a video stream containing output image frames without overlay and corresponding output image frames with overlay, wherein:
• the first input image frame is encoded as an intra-frame to form a first output image frame,
• the second input image frame is encoded as an inter-frame with reference to the first output image frame to form a second output image frame,
• the first generated image frame is encoded as an inter-frame with reference to the first output image frame to form a first overlaid output image frame,
• the second generated image frame is encoded as an inter-frame to form a second overlaid output image frame, wherein a first part of the second generated image frame is encoded with reference to the first overlaid output image frame, and a second part of the second generated image frame is encoded with reference to the second output image frame.