Apple Inc.

Maynard J Handley

Hsi-Jung Wu

Thomas Pun

Xiaochun Nie

Roger Kumar

A method for encoding video with a two-dimensional (2D) transform separable to two one-dimensional (1D) transforms. The method receives an array of values for a sub-section of an image, performs a first 1D-transform of the array, transposes the resulting array, and performs a second 1D-transform of the array resulting from the transpose. The method, without performing another transpose, generates a data stream using a transposed scan order based on the values of the array resulting from the second transform. A method for decoding video encoded by a 2D transform, which separable to two 1D transforms. The method receives a data stream containing encoded values for an image, parses out the values into an array using a transposed scan order, performs a first 1D-inverse transform on the array, transposes the resulting array, and performs a second 1D-inverse transform of the array resulting from the transpose to produce a decoded output.

Efficient video encoding by preforming transform operations

Some embodiments of the invention provide a method of decoding an encoded video signal that includes a plurality of successive encoded images. The method initially receives an encoded image of the video signal. It then decodes the encoded image. The method next examines the decoded image to determine whether the decoded image satisfies at least one criterion for performing a post-filter operation on the decoded image. Only if the decoded image satisfies the criterion, the method performs the post-filter operation on the decoded image. The criterion in some embodiments is whether the amount of time for applying the post-filter operation exceeds the remaining amount of time that the method has to process the received image. Some embodiments of the invention provide a method of post-filtering a current image that was decoded from an encoded video signal, which includes a plurality of successive encoded images. The current image has several sub-sections. The method selects a sub-section of the current image. It then determines whether the selected sub-section satisfies at least one condition for performing a post-filter operation on the selected sub-section. The method next performs the post-filter operation on the selected sub-section only if the selected sub-section satisfies the criterion.

Adaptively post filtering encoded video

Some embodiments of the invention provide a method of performing a Discrete Cosine Transform ('DCT') encoding or decoding coefficients of a data array by (1) multiplying the coefficients by a scalar value before the encoding or decoding, and then (2) dividing the encoded or decoded coefficients by the scalar value. When used in conjunction with fixed-point arithmetic, this method increases the precision of the encoded and decoded results. In addition, some embodiments provide a method of performing a two-dimensional (2D) Inverse Discrete Cosine Transform ('iDCT'). This method splits a pre-multiplication operation of the iDCT into two or more separate stages. When used in conjunction with fixed-point arithmetic, this splitting increases the precision of the decoded results of the iDCT.

Encoding and decoding data arrays

A method of implementing a two-dimensional Inverse Discrete Cosine Transform on a block of input data. The method includes 1) generating a performance array for the columns of the input data; 2) performing a column-wise IDCT upon the input data, the IDCT performed in accordance with cases given for each of the columns by the performance array; (3) generating a row performance offset for rows of the input data; and 4) performing a row-wise IDCT upon the result data from the performing of the column-wise IDCT.

Method and apparatus for inverse discrete cosine transform

Video encoding and decoding

A method and apparatus in a computer system for decoding and displaying video frames. An estimated number of intraframes which can be decoded in a current interframe run is determined. Based upon the estimated number of intraframes, determining an adjusted time interval in which to display each intraframe in the current interframe run. The intraframes are then displayed at the adjusted time interval in the current interframe run. The adjusted time interval may include equal time periods for displaying the estimated number of intraframes within the current interframe run. Discontinuities in display of moving video sequences can be avoided.

Frame display dilation in video decoding

A method and apparatus in a computer system for decoding variable length codes (VLC's). Upon receiving a sample VLC from the bitstream, it is determined whether it has a predetermined relationship with a first pattern. The first pattern includes a first portion having a predetermined pattern. A length of the first portion of the sample VLC corresponds to an optimum number of cache lines. If the sample VLC has the predetermined relationship with the first pattern, then the sample VLC is used to retrieve a first decoded value from a first table. Otherwise, if the sample VLC does not have the predetermined relationship with the first pattern, then the sample VLC is used to retrieve a second decoded value from a second table.

Growing community of inventors

Cupertino, CA, United States of America

Maynard J Handley