Film grain synthesis is a powerful tool that can significantly reduce the bitrate of a grainy video. It is typically used with noise removal before the compression, which can make banding more pronounced in the compressed video. When the synthesized grain is added, the banding can still be visible, even at mid QPs. This article describes three algorithms that can be used with the AV1/AV2 film grain synthesis to reduce visibility of underlying bands in the re-noised video. These changes to the film grain synthesis algorithm are computationally inexpensive and improve the perceptual video quality when banding is present.

This paper discusses sources of banding artifacts present in video codecs using an example of the AVM video codec and proposes solutions that help to significantly reduce these artifacts. The proposed approach shows a reduction of banding observed by visual inspection and a decrease in banding according to an objective banding metric. The approach does not add new tools to the video codec. There is a penalty of 1.32% in the PSNR-YUV BD-rate observed on a range of test sequences. The proposed solutions can also be applied to other hybrid video codecs.

Film grain is abundant in TV and movie content. It is often part of the creative intent and needs to be preserved while encoding. However, the random nature of film grain is difficult to compress using traditional coding tools. This paper describes a film grain modeling and synthesis algorithm proposed for the AV1 video codec. At the encoder, an autoregressive model of film grain is transmitted relative to a denoised signal, and the film grain strength is modeled as a function of intensity. The corresponding renoising at the decoder is implemented using an efficient block-based approach suitable for use in consumer electronic devices. Preliminary results indicate that the approach can give significant bitrate savings (up to 50%) on sequences with heavy film grain.

The paper addresses a problem of perceptual artifacts that appear in Y'CbCr non-linear luminance 4:2:0 HDR video. A computationally inexpensive method is proposed for converting the 4:4:4 HDR video to Y'CbCr 4:2:0 nonconstant luminance format. The method removes artifacts in areas with saturated colors. The approach obtains results in one step, improving the average linear light PSNR by 2.16 dB and tPSNR metric by 1.99 dB on the investigated videos.