摘要:
Methods for pre-processing video sequences prior to compression to provide data reduction of the video sequence. In addition, after compression of the pre-processed video sequence, the bit rate of the pre-processed and compressed video sequence will be lower than the bit rate of the video sequence after compression but without pre-processing. A temporal filtering method is provided for pre-processing of video frames of a video sequence. In the method, pixel values of successive frames are filtered when the difference in the pixel values between the successive frames are within high and low threshold values. The high and low threshold values are determined adaptively depending on the illumination level of a video frame to provide variability of filtering strength depending on the illumination levels of a video frame.
摘要:
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. Examples of such categorizations include: (1) category 1 images, which are images at natural scene changes or images that collectively capture a fast motion, (2) category 2 images, which are imaged forced to be intrablock encoded and are not category 1 images, (3) category 3 images, which are images that should be easy to encode, (4) category 4 images, which are images at the transition between simple and difficult images, and (5) category 5 images, which are images that do not fall in the other categories. In some embodiments, the sequence of frames is divided into a set of blocks, where each block has (1) a size and (2) a bit allocation. Some embodiments dynamically adjust the size of the blocks during the encoding operation. In some embodiments, unused bits allocated to a first block are rolled over to a second block. In other embodiments, only some of the unused bits are rolled over to the second block.
摘要:
Some embodiments of the invention provide a multi-pass encoding method that encodes several images (eg., several frames of a video sequence). The method iteratively performs an encoding operation that encodes these images. The encoding operation is based on a nominal quantization parameter, which the method uses to compute quantization parameters for the images. During several different iterations of the encoding operation, the method uses several different nominal quantization parameters. The method stops its iterations when it reaches a terminating criterion (e.g., it identifies an acceptable encoding of the images).
摘要:
Some embodiments provide a method that provides a graphical user interface (GUI) on a first device for controlling application of color corrections to a media item by a media editing application on a second device. The method provides a display area that includes several different locations. Each location in the display area corresponds to a set of values. The method provides several user interface (UI) items that are each for (1) moving in the display area and (2) specifying a set of values for a color correction operation that the media editing application applies to the media item. The set of values for the color correction operation specified by each UI item is the set of values is associated with the location at which the UI item is positioned in the display area.
摘要:
Some embodiments of the invention provide a non-linear image-enhancement method to enhance an image that includes a number of picture elements. The non-linear enhancement method adjusts the brightness value of each pixel in the image and adjusts at least one chromatic value of each pixel in the image based on the adjustment to the brightness value of that pixel.
摘要:
Systems and methods for reducing bit rates by replacing original texture in a video sequence with synthesized texture. Reducing the bit rate of the video sequence begins by identifying and removing selected texture from frames in a video sequence. The removed texture is analyzed to generate texture parameters. New texture is synthesized using the texture parameters in combination with a set of constraints. Then, the newly synthesized texture is mapped back into the frames of the video sequence from which the original texture was removed. The resulting frames are then encoded. The bit rate of the video sequence with the synthesized texture is less than the bit rate of the video sequence with the original texture. Also, the ability of a decoder to decode the new video sequence is not compromised because no assumptions are made about the texture synthesis capabilities of the decoder.
摘要:
Methods for pre-processing video sequences prior to compression to provide data reduction of the video sequence. Also, after compression of the pre-processed video sequence, the bit rate of the pre-processed and compressed video sequence will be lower than the bit rate of the video sequence after compression but without pre-processing. Pre-processing may include spatial anisotropic diffusion filtering such as Perona-Malik filtering, Fallah-Ford filtering, or omni-directional filtering that extends Perona-Malik filtering to perform filtering in at least one diagonal direction. Pre-processing may also include performing filtering differently on a foreground region than on a background region of a video frame. This method includes identifying pixel locations having pixel values matching characteristics of human skin and determining a bounding shape for each contiguous grouping of matching pixel locations. The foreground region is comprised of pixel locations contained in a bounding shape and the background region is comprised of all other pixel locations.