Abstract: Techniques and tools are described for using quantization bias that accounts for relations between transform bins and quantization bins. The techniques and tools can be used to compensate for mismatch between transform bin boundaries and quantization bin boundaries during quantization. For example, in some embodiments, when a video encoder quantizes the DC coefficients of DC-only blocks, the encoder compensates for mismatches between transform bin boundaries and quantization bin boundaries. In some implementations, the mismatch compensation uses an offset table that accounts for the mismatches. In other embodiments, the encoder uses adjustable thresholds to control quantization bias.

Abstract: Quality settings established by an encoder are adjusted based on information associated with regions of interest (“ROIs”). For example, quantization step sizes can be reduced (to improve quality) or increased (to reduce bit rate). ROIs can be identified and quality settings can be adjusted based on input received from a user interface. An overlap setting can be determined for a portion of a picture that corresponds to an ROI overlap area. For example, an overlap setting is chosen from step sizes corresponding to a first overlapping ROI and a second overlapping ROI, or from relative reductions in step size corresponding to the first ROI and the second ROI. ROIs can be parameterized by information (e.g., using data structures) that indicates spatial dimensions of the ROIs and quality adjustment information (e.g., dead zone information, step size information, and quantization mode information).

Abstract: Techniques and tools are described for adaptive deadzone (“DZ”) resizing during quantization. For example, in some embodiments, for quantization of an AC frequency coefficient of a block, a video encoder adjusts DZ size of a selected quantizer depending on the texture of the block. In other embodiments, a video encoder adjusts DZ size depending on the frequency of a coefficient being quantized. In still other embodiments, for quantization of an AC frequency coefficient of a block, a video encoder adjusts DZ size depending on the texture of the block and the frequency of the coefficient being quantized.

Abstract: Techniques and tools for encoding and decoding video images (e.g., interlaced frames) are described. For example, a video encoder or decoder processes 4:1:1 format macroblocks comprising four 8×8 luminance blocks and four 4×8 chrominance blocks. In another aspect, fields in field-coded macroblocks are coded independently of one another (e.g., by sending encoded blocks in field order). Other aspects include DC/AC prediction techniques and motion vector prediction techniques for interlaced frames.

Abstract: Multiple-pass video encoding systems and techniques are described which utilize statistics taken during a first-pass encoding to create complexity measurements for video data which is to be encoded. By analyzing these complexity measurements, preprocessing decisions, such as, for example, the determination of strength of denoise filters, can be made with greater accuracy. In one implementation, these complexity measurements take the form of calculation of temporal and spatial complexity parameters, which are then used to compute a unified complexity parameter for each group of pictures being encoded.

Abstract: A video encoder performs multi-resolution video coding. For example, the encoder adaptively changes frame sizes to reduce blocking artifacts at low bitrates. A video decoder performs corresponding multi-resolution decoding.

Abstract: Techniques and tools for deriving chroma motion vectors for macroblocks of interlaced forward-predicted fields are described. For example, a video encoder or decoder determines a prevailing polarity among luma motion vectors for a macroblock. The encoder or decoder then determines a chroma motion vector for the macroblock based at least in part upon one or more of the luma motion vectors having the prevailing polarity.

Abstract: Techniques and tools for sub-block transform coding are described. For example, a video encoder adaptively switches between 8×8, 8×4, and 4×8 DCTs when encoding 8×8 prediction residual blocks; a corresponding video decoder switches between 8×8, 8×4, and 4×8 inverse DCTs during decoding. The video encoder may determine the transform sizes as well as switching levels (e.g., frame, macroblock, or block) in a closed loop evaluation of the different transform sizes and switching levels. The encoder and decoder may use different scan patterns for different transform sizes when scanning values from two-dimensional blocks into one-dimensional arrays, or vice versa. The encoder and decoder may use sub-block pattern codes to indicate the presence or absence of information for the sub-blocks of particular blocks.

Abstract: Techniques and tools for processing reference frames in a motion estimation/compensation loop or motion compensation loop are described. For example, a video encoder or decoder filters reference frames to reduce discontinuities at block boundaries, improving the efficiency of motion estimation and compensation.

Abstract: In one aspect, an encoder/decoder selects a bitplane mode from a group of plural available bitplane modes, and processes a bitplane according to the selected bitplane mode, wherein the bitplane indicates AC prediction status information for plural macroblocks of a video picture. In another aspect, an encoder encodes a bitplane that indicates AC prediction status information for plural macroblocks of a video picture and signals the encoded bitplane. In another aspect, a decoder receives an encoded bitplane and decodes the bitplane, wherein the bitplane indicates AC prediction status information for plural macroblocks of a video picture.

Abstract: In one aspect, for a first interlaced video frame in a video sequence, a decoder decodes a bitplane signaled at frame layer for the first interlaced video frame. The bitplane represents field/frame transform types for plural macroblocks of the first interlaced video frame. For a second interlaced video frame in the video sequence, for each of at least one but not all of plural macroblocks of the second interlaced video frame, the decoder processes a per macroblock field/frame transform type bit signaled at macroblock layer. An encoder performs corresponding encoding.

Abstract: A video encoder performs multi-resolution video coding. For example, the encoder adaptively changes frame sizes to reduce blocking artifacts at low bitrates. A video decoder performs corresponding multi-resolution decoding.

Abstract: Techniques and tools for sub-block transform coding are described. For example, a video encoder adaptively switches between 8×8, 8×4, and 4×8 DCTs when encoding 8×8 prediction residual blocks; a corresponding video decoder switches between 8×8, 8×4, and 4×8 inverse DCTs during decoding. The video encoder may determine the transform sizes as well as switching levels (e.g., frame, macroblock, or block) in a closed loop evaluation of the different transform sizes and switching levels. The encoder and decoder may use different scan patterns for different transform sizes when scanning values from two-dimensional blocks into one-dimensional arrays, or vice versa. The encoder and decoder may use sub-block pattern codes to indicate the presence or absence of information for the sub-blocks of particular blocks.

Abstract: Techniques and tools for processing reference frames in a motion estimation/compensation loop or motion compensation loop are described. For example, a video encoder or decoder filters reference frames to reduce discontinuities at block boundaries, improving the efficiency of motion estimation and compensation.