Patent ID: 8406293

Claim:
A method of iteratively encoding a video sequence comprising a plurality of images using a plurality of encoding passes, the method comprising: for a first encoding pass, specifying a first nominal quantization parameter by a video encoder; during the first encoding pass, encoding each image by (i) generating a separate image-specific quantization parameter for the image by using the first nominal quantization parameter and a masking strength parameter that provides a degree of visual masking that quantifies an amount of coding artifacts that would be hidden for the image and (ii) encoding the image by performing a quantization operation on the image using the image-specific quantization parameter generated during the first encoding pass; for a second encoding pass, specifying a second nominal quantization parameter different than the first nominal quantization parameter; and during the second encoding pass, encoding each image by (i) generating a separate image-specific quantization parameter for the image by using the second nominal quantization parameter and the masking strength parameter for the image and (ii) encoding the image by performing a quantization operation on the image using the image-specific quantization parameter generated during the second encoding pass, wherein for each image in a set of images in the video sequence, the image-specific quantization parameter that is generated during the second encoding pass is different than the image-specific quantization parameter that is generated during the first encoding pass.