Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Dynamic packet size control for mpeg-4 data partition mode

The present application is a divisional of and claims the benefit of U.S. patent application Ser. No. 10/721,709, filed Nov. 25, 2003, entitled “DYNAMIC PACKET SIZE CONTROL FOR MPEG-4 DATA PARTITION MODE,” naming Ram Prabhakar, Harikrishna M. Reddy, Lefan Zhong, Wei Sun, Leonardo Vainsencher, and Visalakshi Vaduganathan as inventors, assigned to the assignee of the present invention, and having attorney docket number NVID-P000899. That application is incorporated herein by reference in its entirety and for all purposes.

The present application is related to U.S. patent application Ser. No. ______,filed Dec. ______, 2007, entitled “DYNAMIC PACKET SIZE CONTROL FOR MPEG-4 DATA PARTITION MODE,” naming Ram Prabhakar, Harikrishna M. Reddy, Lefan Zhong, Wei Sun, Leonardo Vainsencher, and Visalakshi Vaduganathan as inventors, assigned to the assignee of the present invention, and having attorney docket number NVID-P000899.D2. That application is incorporated herein by reference in its entirety and for all purposes.

The invention generally relates to computer systems, and more particularly relates to dynamic packet size control in MPEG-4 data partition mode.

Moving Pictures Experts Groups (MPEG) is an International Standards Organization (ISO) standard for compressing video data. Video compression is important in making video data files, such as full-length movies, more manageable for storage (e.g., in optical storage media), processing, and transmission. In general, MPEG compression is achieved by eliminating redundant and irrelevant information. Because video images typically consist of smooth regions of color across the screen, video information generally varies little in space and time. As such, a significant part of the video information in an image is predictable and therefore redundant. Hence, a first objective in MPEG compression is to remove the redundant information and leaving only the true or unpredictable information. On the other hand, irrelevant video image information is information that cannot be seen by the human eye under certain reasonable viewing conditions. For example, the human eye is less perceptive to noise at high spatial frequencies than noise at low spatial frequencies and less perceptive to loss of details immediately before and after a scene change. Accordingly, the second objective in MPEG compression is to remove irrelevant information. The combination of redundant information removal and irrelevant information removal allows for highly compressed video data files.

MPEG compression incorporates various well-known techniques to achieve the above objectives including: motion-compensated prediction, Discrete Cosine Transform (DCT), quantization, and Variable-Length Coding (VLC). DCT is an algorithm that converts pixel data into sets of spatial frequencies with associated coefficients. Due to the non-uniform distribution of the DCT coefficients wherein most of the non-zero DCT coefficients of an image tend to be located in a general area, VLC is used to exploit this distribution characteristic to identify non-zero DCT coefficients from zero DCT coefficients. In so doing, redundant/predictable information can be removed. Additionally, having decomposed the video image into spatial frequencies under DCT means that higher frequencies via their associated DCT coefficients can be coded with less precision than the lower frequencies via their associated DCT coefficients thereby allowing irrelevant information to be removed. Hence, quantization may be generalized as a step to weight the DCT coefficients based on the amount of noise that the human eye can tolerate at each spatial frequency so that a reduced set of coefficients can be generated.

Additionally, MPEG compression also includes additional compression stages such as Alternative Coefficient/Discrete Coefficient (AC/DC) prediction. AC is typically defined as a DCT coefficient for which the frequency in one or both dimensions is non-zero (higher frequency). DC is typically defined as a DCT coefficient for which the frequency is zero (low frequency) in both dimensions. An AC/DC prediction module predicts the AC and DC for the current block based on AC and DC values of adjacent blocks such as an adjacent left top block, a top block, and an adjacent left block. For example, the prediction can be made as follows:

If (|B−A|≧|B−C) then X=A else X=C where B is the AC or DC value of the left top block relative to the current block, C is the AC or DC value of the top block relative to the current block, A is the AC or DC value of the left block relative to the current block, and X is the AC or DC value of the current block.