Patent Application
20060222247
[Not Applicable]
[Not Applicable]
There are a number of different standards that are available for compressing video data. These standards include standards promulgated by the Motion Picture Experts Group (MPEG). The standards promulgated by MPEG include MPEG-2, and MPEG-4, Part 10 (also known as Advanced Video Coding and also known and now referred to as H.264).
A number of video decoder systems are capable of decoding both MPEG-2 and H.264. However, VC-1 is a recent standard promulgated by the Society for Motion Pictures and Television Engineers (SMPTE) and promoted by Microsoft Corporation. Although there are similarities between VC-1 and H.264, VC-1 also includes a number of differences.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.
Presented herein are hardware implementations for inverse scanning for a plurality of standards, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
These and other advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
Referring now to
The scanning techniques used depend on the encoding standard. The encoding standards include standards promulgated by the Motion Picture Experts Group (MPEG) and that promulgated by the Society for Motion Pictures and Television Engineers (SMPTE) and promoted by Microsoft Corporation. The standards promulgated by MPEG include MPEG-2 and MPEG-4, Part 10 (also known as Advanced Video Coding and also known and now referred to as H.264). VC-1 is a standard promulgated by the SMPTE, and promoted by Microsoft Corporation (as WM9 or Windows Media 9).
Referring now to
The entropy pre-processor 205 receives encoded video data. The encoded video data can comprise entropy coded symbols. The entropy pre-processor 205 decodes the entropy coded symbols. The entropy pre-processor 205 writes the symbols to the coded data buffer 210. The variable length decoder 215 decodes variable length codes in the encoded video data.
The foregoing results in quantized frequency coefficients 110 and macroblock headers. The inverse quantizer 230 inverse quantizes the quantized frequency coefficients 110, resulting in frequency coefficients 105. The inverse transformer 240 inverse transforms the frequency coefficients 105, resulting in pixel data. The motion compensator 245 motion compensates the pixel data, using previously decoded pictures 100 stored in the frame buffers 255.
Referring now to
AC Prediction:
The AC predictor 325 performs AC prediction if AC prediction is enabled for the current block under decode. AC prediction is present in the VC-1 video standard. The DC-Predictor 320 supplies the prediction direction and the prediction data will be from either the top row or the left column. The prediction coefficients are written to a DRAM.
DC Transform:
The DC transformer 315 performs matrix multiplication of the DC-only luma and chroma sub-blocks of AVC with the constant matrix. The constant matrix has signed unit coefficients. Based on this fact, matrix multiplication is performed by add-accumulate operation. There are two passes in the DC transform for two set of matrix multiplication.
Inverse Quantization:
The inverse quantization engine 330 supports inverse quantization for a plurality of video encoding standards. In certain embodiments of the present invention, seven types of the inverse quantization present based on the block-type (video standard under decode), where MPEG2 has two types, AVC has three types and VC-1 has two types, are supported. The type of the Inverse quantization depends on the macro-block type and Luma-chroma blocks (sub-blocks). The inverse quantizer can comprise the inverse quantizer described in U.S. patent application Ser. No. ______, “Optimized Single Inverse Quantization Engine for a Plurality of Standards”, filed by Sherigar on ______.
Run-Level Decoder/DC Prediction/Inverse Scan
The run level decoder/inverse scanner 320 and DC predictor 320 can be clubbed in a single data path if their operations are sequentially dependent. The run level decoder/inverse scanner 310 does the “zero” filling operation, decided by the run count of the current run-level pair. DC predictor 320 performs DC prediction if DC prediction is enabled for the current block. This is present in intra blocks of VC-1. This is done by choosing the prediction direction, which is based on the relative DC values of the neighboring left, top and diagonal blocks.
The inverse scan operation is accomplished by providing a correct address of a buffer based on a lookup table value. These lookup table values are programmed during the picture level initialization.
Referring now to
The inverse scanner 310 is controlled by control processor 225. At the beginning of each picture, the control processor 225 loads the scan table RAM 405 with the tables associated with the encoding standard for the video data. In certain embodiments, control processor 225 can load the scan table RAM 405 with the tables for inverse scanning that are associated with the MPEG-2, H.264, and VC-1 standards.
The inverse scan datapath logic 410 receives input control signals indicating the encoding standard of the picture, the type of scan, and an address to the scan table RAM 405. The address points to the scan address in the scan table RAM 405 at which the appropriate inverse scanning table for inverse scanning the video data is stored. The output of the RAM 405 is used as the address for storing the frequency coefficients in double buffer 415. The double buffer 415 stores the frequency coefficients in one portion. The inverse scanning engine 410 writes the inverse scanned frequency coefficients to the another portion of the double buffer 415.
Referring now to
At 505, at the beginning of the picture, the control processor 225 loads the scan table 405 with tables associated with the encoding standard for the video data. In certain embodiments, control processor 225 can load the scan table RAM 405 with the tables for inverse scanning that are associated with the MPEG-2, H.264, and VC-1 standards.
At 510, the inverse scan control unit 420 provides the input control signals indicating the encoding standard of the picture, TYPE, the type of scan, SCAN, and an address to the scan table RAM 405, ADDR.
At 515, the inverse scan datapath 410 sends the address to read from the address ADDR in the scan table RAM 405 and applies the table to the frequency coefficients, to store in double buffer. The double buffer 415 stores the frequency coefficients in one portion. The inverse scanning engine 410 writes the inverse scanned frequency coefficients to the another portion of the double buffer 415. After 515, if at 520 the picture is completed, 505 is repeated. If not, 510 is repeated.
The embodiments described herein may be implemented as a board level product, as a single chip, application specific integrated circuit (ASIC), as part of an ASIC containing other functions, or with varying levels of the decoder system integrated with other portions of the system as separate components.
The degree of integration of the decoder system may primarily be determined by the speed and cost considerations. Because of the sophisticated nature of modern processor, it is possible to utilize a commercially available processor, which may be implemented external to an ASIC implementation. If the processor is available as an ASIC core or logic block, then the commercially available processor can be implemented as part of an ASIC device wherein certain functions can be implemented in firmware. Alternatively, the functions can be implemented as hardware accelerator units controlled by the processor.
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. For example, the inverse scanning can occur before or after the inverse quantization. Accordingly, the term “frequency coefficients” shall be understood to cover both quantized and inverse quantized frequency coefficients. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope.
Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.
