Abstract: Some embodiments of the invention provide a method for specifying a bit allocation for encoding a set of images in a sequence of video images. The method computes a masking value for one or more images. The method computes a bit allocation for a current image based on the computed masking value of one or more images. In some embodiments, the method further ascertains a total number of bits used for images that have been already encoded before computing the bit allocation. The computed bit allocation for the current image is also based on the total number of bits used in some embodiments of the invention. In some embodiments, the method specifies a bit allocation for the current image by specifying a quantization parameter (QP) value for the current image. The method then adjusts the specified QP value based on a categorization of the current image.

Abstract: Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved.

Abstract: Some embodiments provide a method for encoding a first set of pixels in a first image by reference to a second image in a video sequence. In a first search window within a second image, the method searches to identify a first particular portion in the second image that best matches the first set of pixels in the first image. In the first search window within the second image, the method identifies a first location corresponding to the first particular portion. In a second search window within the second image, the method then searches to identify a second particular portion in the second image that best matches the first set of pixels in the first image, where the second search window is defined about the first location.

Abstract: Some embodiments provide a method for encoding a first set of pixels in a first image in a sequence of images. From a set of encoding modes, the method of some embodiments selects a first mode for encoding the first set of pixels. The method then determines whether encoding the first set of pixels in the first mode satisfies a set of quality criteria. The method foregoes encoding the first set of pixels in a second mode from the set of encoding modes, when the first mode encoding satisfies the set of quality criteria. Some embodiments provide a video encoding method that examines several different methods for encoding a set of pixels in a first image. From a list of possible encoding modes, the method eliminates a set of encoding modes that are not likely to provide a suitable encoding solution. The method then examines different encoding solutions based on the remaining encoding modes in the list.