Efficient Flicker-Free Tone mapping of HDR Videos

Tone mapping is necessary for Low Dynamic Range (LDR) devices to display High Dynamic Range (HDR) images and videos. Multiple video Tone Mapping Operators (vTMOs) have been devised for HDR videos. The majority of vTMOs apply an image TMO to each video frame. This is followed by pre/post filtering to ensure temporal coherence. However, this destroys the natural temporal variation in intensity that is inherent in a changing scene. Furthermore, in these methods computational complexity of an image TMO is scaled up in proportion to the number of frames. We propose an efficient method to extend an image TMO to video TMO. The proposed method is general and takes care of temporally coherent intensity variation between frames while addressing the well-known issue of flickering in tone mapped video. Additionally, it lowers computational complexity as a new tone mapping curve (TMC) is not generated on per frame basis. The proposed vTMO can be used to extend any state-of-the-art global TMO that is deemed to generate a TMC. Fresh TMC is generated only when a hard cut in video is detected or the global change in illumination in HDR video becomes large enough. Visual comparisons and objective evaluations with three well known image TMOs demonstrate that the suggested extension method generates high quality LDR video generally at low computational cost when compared to existing vTMOs. Further work on efficient implementation of embedding an image TMO in our vTMO algorithm is expected to yield even better computational efficiency.