Apple Inc.

Other

Roger Kumar

Thomas Pun

Hsi-Jung Wu

Xiaochun Nie

Maynard J Handley

Hsi Jung Wu

Method For Implementing A Quantizer In A Multimedia Compression And Encoding System is disclosed. In the Quantizer system of the present invention, several new quantization ideas are disclosed. In one embodiment, adjacent macroblocks are grouped together into macroblock groups. The macroblock groups are then assigned a common quantizer value. The common quantizer value may be selected based upon how the macroblocks are encoded, the type of macroblocks within the macroblock group (intra-blocks or inter-blocks), the history of the motion vectors associated with the macroblocks in the macroblock group, the residuals of the macroblocks in the macroblock group, and the energy of the macroblocks in the macroblock group. The quantizer value may be adjusted in a manner that is dependent on the current quantizer value. Specifically, if the quantizer value is at the low end of the quantizer scale, then only small adjustments are made. If the quantizer value is at the high end then larger adjustments may be made to the quantizer. Finally, in one embodiment, the quantizer is implemented along with an inverse quantizer for efficient operation.

Method for implementing a quantizer in a multimedia compression and encoding system

A method for encoding a first set of pixels in a first image in a sequence of images is described. From a set of encoding modes, the method 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. The method also provides 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.

Encoding mode pruning during video encoding

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

A rate controller for allocating a bit budget for video frames to be encoded is disclosed. The rate controller of the present invention considers many different factors when determining the frame bit budget including: desired video quality, target bit rate, frame type (intra-frame or inter-frame), frame duration, intra-frame frequency, frame complexity, intra-block frequency within an intra-frame, buffer overflow, buffer underflow, and the encoded video frame quality for a possible second pass.

Method of performing rate control for a compression system

Some embodiments of the invention provide a method for encoding a video signal that is formed by a series of successive images. Each image includes several sections, and each section has a set of image values. To encode a particular section of a particular image, the method initially partitions the particular section into several sub-sections. For each of at least two particular sub-sections, the method then computes a statistical parameter regarding the image values of the particular sub-section. The method compares the computed statistical parameters, and based on the comparison, selects an encoding technique from a set of encoding techniques to encode the particular section. In some embodiments, the set of encoding schemes includes a first scheme that encodes the selected section without reference to any other section of any other image, and a second scheme that encodes the selected section by reference to at least one other section.

Encoding 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

Some embodiments of the invention provide a method for adaptively performing motion estimation. In some embodiments, the method initially performs a first motion estimation operation. It then determines whether the estimated error in the result of the first motion estimation is greater than a particular threshold. If not, the method uses the results of the first motion estimation operation. Otherwise, the method selects another motion estimation operation. The method continues in this manner until it performs a motion estimation operation that results in an acceptable estimated error, or until it tries all the motion estimation operations at its disposal. When the method cannot identify a motion estimation operation that produces results with an acceptable estimated error, the method selects the result of the motion estimation operation that produced the best results.

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San Francisco, CA, United States of America

Roger Kumar