Abstract: Systems and methods for processing image data in RGB format are provided. In one example, an electronic device includes memory to store image data in raw or RGB format, or both, and an RGB image processing pipeline to process the image data. Specifically, the RGB image processing pipeline may process the image data regardless of whether the image data is of raw or RGB format. The RGB image processing pipeline may include receiving logic to receive the image data in raw or RGB format and demosaicing logic to, when the receiving logic receives the image data in raw format, convert the image data into RGB format. The logic may include local tone mapping logic configured to apply spatially varying tone curves to the image data, a color correction matrix configured to correct color in the image data, and gamma logic configured to transform the image data into gamma space.

Abstract: Systems and methods are provided for collecting image statistics using a pixel mask. In one example, statistics collection logic of an image signal processor may include a pixel weighting mask and accumulation logic. The pixel weighting mask may receive a first representation of a pixel that includes a luma and chroma representation of the pixel. The pixel weighting mask may output a pixel weighting using first and second chroma components of the luma and chroma representation of the pixel. The accumulation logic may receive the first or a second representation of the pixel and the pixel weighting value. Using these, the accumulation logic may weight the second representation of the pixel or the first representation of the pixel using the pixel weighting value to obtain a weighted pixel value, adding the weighted pixel value to a statistics count.

Abstract: In a coding system, an encoder codes video data according to a predetermined protocol, which, when decoded causes an associated decoder to perform a predetermined sequence of decoding operations. The encoder may perform local decodes of the coded video data, both in the manner dictated by the coding protocol that is at work and also by one or more alternative decoding operations. The encoder may estimate relative performance of the alternative decoding operations as compared to a decoding operation that is mandated by the coding protocol. The encoder may provide identifiers in metadata that is associated with the coded video data to identify such levels of distortion and/or levels of resources conserved. A decoder may refer to such identifiers when determining when to engage alternative decoding operations as may be warranted under resource conservation policies.

Abstract: A method of signaling additional chroma QP offset values that are specific to quantization groups is provided, in which each quantization group explicitly specifies its own set of chroma QP offset values. Alternatively, a table of possible sets of chroma QP offset values is specified in the header area of the picture, and each quantization group uses an index to select an entry from the table for determining its own set of chroma QP offset values. The quantization group specific chroma QP offset values are then used to determine the chroma QP values for blocks within the quantization group in addition to chroma QP offset values already specified for higher levels of the video coding hierarchy.

Abstract: Methods and apparatus for caching neighbor data in a block processing pipeline that processes blocks in knight's order with quadrow constraints. Stages of the pipeline may maintain two local buffers that contain data from neighbor blocks of a current block. A first buffer contains data from the last C blocks processed at the stage. A second buffer contains data from neighbor blocks on the last row of a previous quadrow. Data for blocks on the bottom row of a quadrow are stored to an external memory at the end of the pipeline. When a block on the top row of a quadrow is input to the pipeline, neighbor data from the bottom row of the previous quadrow is read from the external memory and passed down the pipeline, each stage storing the data in its second buffer and using the neighbor data in the second buffer when processing the block.

Abstract: A block processing pipeline in which blocks are input to and processed according to row groups so that adjacent blocks on a row are not concurrently at adjacent stages of the pipeline. A stage of the pipeline may process a current block according to neighbor pixels from one or more neighbor blocks. Since adjacent blocks are not concurrently at adjacent stages, the left neighbor of the current block is at least two stages downstream from the stage. Thus, processed pixels from the left neighbor can be passed back to the stage for use in processing the current block without the need to wait for the left neighbor to complete processing at a next stage of the pipeline. In addition, the neighbor blocks may include blocks from the row above the current block. Information from these neighbor blocks may be passed to the stage from an upstream stage of the pipeline.

Abstract: Block processing pipeline methods and apparatus in which pixel data from a reference frame is prefetched into a search window memory. The search window may include two or more overlapping regions of pixels from the reference frame corresponding to blocks from the rows in the input frame that are currently being processed in the pipeline. Thus, the pipeline may process blocks from multiple rows of an input frame using one set of pixel data from a reference frame that is stored in a shared search window memory. The search window may be advanced by one column of blocks by initiating a prefetch for a next column of reference data from a memory. The pipeline may also include a reference data cache that may be used to cache a portion of a reference frame and from which at least a portion of a prefetch for the search window may be satisfied.

Abstract: A method of signaling additional chroma QP offset values that are specific to quantization groups is provided, in which each quantization group explicitly specifies its own set of chroma QP offset values. Alternatively, a table of possible sets of chroma QP offset values is specified in the header area of the picture, and each quantization group uses an index to select an entry from the table for determining its own set of chroma QP offset values. The quantization group specific chroma QP offset values are then used to determine the chroma QP values for blocks within the quantization group in addition to chroma QP offset values already specified for higher levels of the video coding hierarchy.

Abstract: A method for encoding a picture is disclosed. The method generally includes the steps of (A) generating at least one respective macroblock statistic from each of a plurality of macroblocks in the picture, (B) generating at least one global statistic from the picture and (C) generating a respective macroblock quantization parameter for each of the macroblocks based on both (i) the at least one respective macroblock statistic and (ii) said at least one global statistic.

Abstract: Methods and apparatus for caching reference data in a block processing pipeline. A cache may be implemented to which reference data corresponding to motion vectors for blocks being processed in the pipeline may be prefetched from memory. Prefetches for the motion vectors may be initiated one or more stages prior to a processing stage. Cache tags for the cache may be defined by the motion vectors. When a motion vector is received, the tags can be checked to determine if there are cache block(s) corresponding to the vector (cache hits) in the cache. Upon a cache miss, a cache block in the cache is selected according to a replacement policy, the respective tag is updated, and a prefetch (e.g., via DMA) for the respective reference data is issued.

Abstract: A context switching method for video encoders that enables higher priority video streams to interrupt lower priority video streams. A high priority frame may be received for processing while another frame is being processed. The pipeline may be signaled to perform a context stop for the current frame. The pipeline stops processing the current frame at an appropriate place, and propagates the stop through the stages of the pipeline and to a transcoder through DMA. The stopping location is recorded. The video encoder may then process the higher-priority frame. When done, a context restart is performed and the pipeline resumes processing the lower-priority frame beginning at the recorded location. The transcoder may process data for the interrupted frame while the higher-priority frame is being processed in the pipeline, and similarly the pipeline may begin processing the lower-priority frame after the context restart while the transcoder completes processing the higher-priority frame.

Abstract: A block processing pipeline in which macroblocks are input to and processed according to row groups so that adjacent macroblocks on a row are not concurrently at adjacent stages of the pipeline. The input method may allow chroma processing to be postponed until after luma processing. One or more upstream stages of the pipeline may process luma elements of each macroblock to generate luma results such as a best mode for processing the luma elements. Luma results may be provided to one or more downstream stages of the pipeline that process chroma elements of each macroblock. The luma results may be used to determine processing of the chroma elements. For example, if the best mode for luma is an intra-frame mode, then a chroma processing stage may determine a best intra-frame mode for chroma and reconstruct the chroma elements according to the best chroma intra-frame mode.

Abstract: A block input component of a video encoding pipeline may, for a block of pixels in a video frame, compute gradients in multiple directions, and may accumulate counts of the computed gradients in one or more histograms. The block input component may analyze the histogram(s) to compute block-level statistics and determine whether a dominant gradient direction exists in the block, indicating the likelihood that it represents an image containing text. If text is likely, various encoding parameter values may be selected to improve the quality of encoding for the block (e.g., by lowering a quantization parameter value). The computed statistics or selected encoding parameter values may be passed to other stages of the pipeline, and used to bias or control selection of a prediction mode, an encoding mode, or a motion vector. Frame-level or slice-level parameter values may be generated from gradient histograms of multiple blocks.

Abstract: The video encoders described herein may determine an initial designation of a mode in which to encode a block of pixels in an early stage of a block processing pipeline. A component of a late stage of the block processing pipeline (one that precedes the transcoder) may determine a different mode designation for the block of pixels based on coded block pattern information, motion vector information, the position of the block in a row of such blocks, the order in which such blocks are processed in the pipeline, or other encoding related syntax elements. The component in the late stage may communicate information to the transcoder usable in coding the block of pixels, such as modified syntax elements or an end of row marker. The transcoder may encode the block of pixels in accordance with the different mode designation or may change the mode again, dependent on the communicated information.

Abstract: Memory latency tolerance methods and apparatus for maintaining an overall level of performance in block processing pipelines that prefetch reference data into a search window. In a general memory latency tolerance method, search window processing in the pipeline may be monitored. If status of search window processing changes in a way that affects pipeline throughput, then pipeline processing may be modified. The modification may be performed according to no stall methods, stall recovery methods, and/or stall prevention methods. In no stall methods, a block may be processed using the data present in the search window without waiting for the missing reference data. In stall recovery methods, the pipeline is allowed to stall, and processing is modified for subsequent blocks to speed up the pipeline and catch up in throughput. In stall prevention methods, processing is adjusted in advance of the pipeline encountering a stall condition.

Abstract: Blocks of pixels from a video frame may be encoded in a block processing pipeline using wavefront ordering, e.g. according to knight's order. Each of the encoded blocks may be written to a particular one of multiple buffers such that the blocks written to each of the buffers represent consecutive blocks of the frame in scan order. Stitching information may be written to the buffers at the end of each row. A stitcher may read the rows from the buffers in order and generate a scan order output stream for the frame. The stitcher component may read the stitching information at the end of each row and apply the stitching information to one or more blocks at the beginning of a next row to stitch the next row to the previous row. Stitching may involve modifying pixel(s) of the blocks and/or modifying metadata for the blocks.

Abstract: A knight's order processing method for block processing pipelines in which the next block input to the pipeline is taken from the row below and one or more columns to the left in the frame. The knight's order method may provide spacing between adjacent blocks in the pipeline to facilitate feedback of data from a downstream stage to an upstream stage. The rows of blocks in the input frame may be divided into sets of rows that constrain the knight's order method to maintain locality of neighbor block data. Invalid blocks may be input to the pipeline at the left of the first set of rows and at the right of the last set of rows, and the sets of rows may be treated as if they are horizontally arranged rather than vertically arranged, to maintain continuity of the knight's order algorithm.

Abstract: A block processing pipeline that includes a software pipeline and a hardware pipeline that run in parallel. The software pipeline runs at least one block ahead of the hardware pipeline. The stages of the pipeline may each include a hardware pipeline component that performs one or more operations on a current block at the stage. At least one stage of the pipeline may also include a software pipeline component that determines a configuration for the hardware component at the stage of the pipeline for processing a next block while the hardware component is processing the current block. The software pipeline component may determine the configuration according to information related to the next block obtained from an upstream stage of the pipeline. The software pipeline component may also obtain and use information related to a block that was previously processed at the stage.

Abstract: Systems and methods for local tone mapping are provided. In one example, an electronic device includes an electronic display, an imaging device, and an image signal processor. The electronic display may display images of a first bit depth, and the imaging device may include an image sensor that obtains image data of a higher bit depth than the first bit depth. The image signal processor may process the image data, and may include local tone mapping logic that may apply a spatially varying local tone curve to a pixel of the image data to preserve local contrast when displayed on the display. The local tone mapping logic may smooth the local tone curve applied to the intensity difference between the pixel and another nearby pixel exceeds a threshold.

Abstract: Systems and methods for down-scaling are provided. In one example, a method for processing image data includes determining a plurality of output pixel locations using a position value stored by a position register, using the current position value to select a center input pixel from the image data and selecting an index value, selecting a set of input pixels adjacent to the center input pixel, selecting a set of filtering coefficients from a filter coefficient lookup table using the index value, filtering the set of source input pixels to apply a respective one of the set of filtering coefficients to each of the set of source input pixels to determine an output value for the current output pixel at the current position value, and correcting chromatic aberrations in the set of source input pixels.