Method and image-processing device for adding an overlay to a video sequence

A method, performed by an image-processing device, for adding an overlay to a video sequence, the method comprising:

• determining, based on a representation of the overlay stored in one or more buffers or memory areas of the image-processing device, whether or not a content of the overlay is updated within a time period;
• determining, based on whether or not the content of the overlay is determined to be updated within the time period, whether or not to provide, by a Central Processing Unit, CPU, or Graphic Processing Unit, GPU, a compressed representation of the overlay in a compressed format to an image compositor, wherein it is determined to provide the compressed representation of the overlay in response to determining that the content of the overlay is not updated within the time period, and wherein it is determined to not provide the compressed representation of the overlay in response to determining that the content of the overlay is updated within the time period;
• and
• when the compressed representation of the overlay in the compressed format has been provided, decoding and adding, by the image compositor, the compressed representation of the overlay to video data of a video frame of the video sequence if a compression ratio of the compressed representation of the overlay with respect to an uncompressed representation of the overlay in an uncompressed format is above a threshold, while if the compression ratio is below the threshold, adding the uncompressed representation of the overlay to video data of the video frame of the video sequence, and
• when the compressed representation of the overlay in the compressed format has not been provided, adding the uncompressed representation of the overlay to video data of the video frame of the video sequence.