Obviousness

Under 35 U.S.C. § 103, the claims of US Patent 11936876 would have been obvious to a person having ordinary skill in the art (PHOSITA) based on a combination of the prior art explicitly described within the patent's own background section. The core inventive step claimed by the patent is the application of hierarchical block partitioning and signaling, previously established for inter prediction in large blocks, to intra prediction for large blocks.

Identified Prior Art References:

1. MPEG-4 AVC Standard (H.264 Recommendation): This standard, referred to in the patent, describes intra coding for macroblocks of sizes 4×4, 8×8, and 16×16. It details various intra prediction modes (e.g., vertical, horizontal, DC, diagonal, plane) and their signaling mechanisms, including mb_type and transform_8x8_size_flag for differentiating between INTRA4×4 and INTRA8×8, and specific mb_type values for INTRA16×16. [cite: "BACKGROUND", "TABLE 1"]
2. Hierarchical Inter Prediction for Large Blocks: This refers to two related prior art discussions in the patent:
   • "First prior art approach": Describes how signaling is done for 32×32 or 64×64 blocks using a hierarchical coding structure for large motion (Inter) partitions. [cite: "BACKGROUND"]
   • "Further inter coding proposals": Mentions inter coding proposals for extensions of the MPEG-4 AVC Standard using 32×32, 32×16, and 16×32 partitions. It illustrates motion partitions for 32×32 blocks, including further partitioning into 16×16, 16×8, 8×16, and 8×8, and even down to 4×4. Crucially, it states that "SKIP mode or DIRECT mode is signaled using an mb32_skip_flag in a way similar to that performed for other modes of the MPEG-4 AVC Standard." [cite: "BACKGROUND"] Furthermore, it teaches that if a 32×32 inter partition uses 16×16 sub-partitions, "the four 16×16 blocks are signaled in raster scan order by using the same syntax elements as macroblock_layer( ) in the MPEG-4 AVC Standard." [cite: "BACKGROUND"] It also notes that for 64×64 macroblocks, "one more hierarchical layer is added in the macroblock partition above block size 32×32." [cite: "BACKGROUND"]

Obviousness Combination and Motivation:

A PHOSITA in video compression, aiming to enhance the efficiency of video codecs, would have been motivated to combine the intra prediction techniques of the MPEG-4 AVC Standard with the hierarchical block partitioning and signaling methods taught by the Hierarchical Inter Prediction for Large Blocks prior art.

Motivation to Combine:
The MPEG-4 AVC Standard established effective intra prediction for smaller block sizes. [cite: "BACKGROUND"] Simultaneously, extensions to this standard, as described in the "Hierarchical Inter Prediction for Large Blocks" prior art, clearly demonstrated the advantages of using larger block sizes (32×32, 64×64) and hierarchical partitioning for inter prediction, enabling better compression in homogeneous regions and adaptive coding. [cite: "BACKGROUND"] A PHOSITA would naturally recognize that similar benefits could be achieved by applying these large block structures and hierarchical signaling to intra prediction, particularly for high-resolution video where large, uniform areas are common. Extending a successful technique from one prediction domain (inter) to another (intra) within the same block-based coding framework would be a logical and predictable step for improving overall compression efficiency. The patent itself identifies that "the existing literature does not address how large intra mode is signaled," [cite: "BACKGROUND"] but this gap merely highlights an area where a PHOSITA would apply known analogous solutions.

Analysis of Claims 1 and 11 (Representative Independent Claims):

Taking Independent Claim 1 (Decoding Method) as representative, the combination of the prior art renders its elements obvious:

1. Determining that intra prediction is to be performed for the large block (block size equal to or larger than 32×32, greater than basic coding unit size): The MPEG-4 AVC Standard teaches intra prediction. [cite: "BACKGROUND"] The "Hierarchical Inter Prediction for Large Blocks" prior art teaches using and partitioning large blocks (32×32, 64×64). [cite: "BACKGROUND"] A PHOSITA would find it obvious to apply intra prediction to these larger block sizes, recognizing their efficiency for smooth image areas.
2. Decoding a binary split signaling syntax element specifying that the large block is further split into four equally sized sub-blocks: The "Hierarchical Inter Prediction for Large Blocks" prior art explicitly teaches hierarchical coding structures and signaling splits for large inter blocks, using flags like mb32_skip_flag. [cite: "BACKGROUND"] It would be an obvious design choice for a PHOSITA to adapt this known signaling mechanism to indicate splits for intra-predicted large blocks. The use of a binary flag to signal a split decision is a fundamental concept in tree-based coding structures.
3. Decoding an intra prediction mode for the large block that is not further split into four equally sized sub-blocks: The MPEG-4 AVC Standard provides various intra prediction modes for 16×16 blocks (e.g., vertical, horizontal, DC, plane). [cite: "BACKGROUND"] For a large block (e.g., 32×32 or 64×64) that is not split, a PHOSITA would obviously extend or adapt these existing intra prediction modes to operate on the larger block size. The patent's own detailed description confirms this, stating that "For INTRA32×32/INTRA64×64, the same modes as INTRA16×16 are used." [cite: "DETAILED DESCRIPTION"]
4. Partitioning the large block into the four equally sized sub-blocks in response to the decoded binary split signaling syntax element: The physical partitioning of a large block into four equally sized sub-blocks (e.g., 64×64 into four 32×32s, or 32×32 into four 16×16s) is explicitly taught and illustrated in the "Hierarchical Inter Prediction for Large Blocks" prior art (e.g., FIG. 3 and the description of motion partitions). [cite: "BACKGROUND", "FIG. 3"] This step is a direct consequence of the decoded signaling.
5. Decoding a second syntax element indicating a single spatial intra partition type for at least one basic coding unit sized sub-block, the single spatial intra partition type being determinable from among a plurality of spatial intra partition types: The "Hierarchical Inter Prediction for Large Blocks" prior art explicitly states that when inter 32×32 blocks are partitioned into 16×16 sub-blocks, "the four 16×16 blocks are signaled in raster scan order by using the same syntax elements as macroblock_layer( ) in the MPEG-4 AVC Standard." [cite: "BACKGROUND"] Since macroblock_layer() in the MPEG-4 AVC Standard includes signaling for mb_type which, in turn, specifies Intra_4x4, Intra_8x8, and Intra_16x16 [cite: "BACKGROUND", "TABLE 1"] (which the patent defines as sip_type or "spatial intra partition types" [cite: "DETAILED DESCRIPTION"]), it would be obvious for a PHOSITA to apply these existing intra partition types and their associated signaling to the resulting intra-predicted sub-blocks within the hierarchical structure.

Independent Claim 11, which describes the encoding method, is the counterpart to Claim 1 and would be rendered obvious for the same reasons, as it involves performing the analogous encoding steps for the same hierarchical intra prediction signaling scheme. Claims 5 and 15, describing the apparatuses, would likewise be obvious as they simply claim hardware configured to perform the obvious methods.

Therefore, the claims of US11936876 are rendered obvious by the combination of the MPEG-4 AVC Standard and the "Hierarchical Inter Prediction for Large Blocks" prior art.