Microsoft Technology Licensing, LLC

Webtv Networks, Inc.

Webtv Networks Inc. (microsoft)

Shankar Moni

John Allen Tardif

Ankur Varma

Andrew Walters

Padma Parthasarathy

Video deblocking can be implemented in video content processing and delivery environments when displaying decompressed/decoded video information. Discontinuities are identified and smoothed to reduce blockiness, for example at macroblock boundaries in conjunction with Moving Picture Expert Group (MPEG)-based schemes. In exemplary implementation(s), a client device detects discontinuities at or near block boundaries, determines which discontinuities are artificial, and smooths at least those discontinuities that are determined to be artificial. These actions may be accomplished using (i) one or more Laplacian of Gaussian (LoG) operations as applied to both an image and a quantization matrix and (ii) windowed comparisons between values and a threshold resulting from the LoG operations. Alternatively, these actions may be accomplished using a spatio-temporally varying filter. Additionally, in an MPEG context, intra image units may be deblocked using the former approach while non-intra image units may be deblocked using the latter approach.

Video deblocking

Systems and methods for transcoding a transport stream or a video stream. A video stream includes a quantization matrix and a quantization scale that define how DCT frequency coefficients are quantized. A transport stream is transcoded by updating the quantization matrix and/or the quantization scale such that a new set of DCT frequency coefficients may be generated. Typically the quantization scale and/or the quantization matrix are updated such that the DCT frequency coefficients are more coarsely quantized such that their encoding consumes fewer bits. The quantization matrix can be updated such that select frequency coefficients are affected. Transcoding can operate at any level of the video stream, such as the frame level, the slice level, or the macroblock level. The bit rate of the video stream can therefore be adjusted or altered according to a current quantization level and a current bit rate.

Non-compensated transcoding of a video stream

Transcoding of a video stream to reduce the size of the video stream with little, if any, loss in video quality after subsampling. After accessing a video stream of video pictures (i.e., video frames or fields), the blocks of the video picture are each subject to matrix pre-multiplication and post-multiplication. Such matrix multiplication does degrade the video quality if subsampling was not to occur. However, the pre-multiplication and post-multiplication matrices are calculated based on the subsampling matrices that will be used to ultimately subsample the video stream such that after subsampling eventually occurs, the matrix multiplications result in minimal loss of video quality.

Methods and systems for compressing a video stream with minimal loss after subsampled decoding

Dynamic rate control can be implemented in a television-based entertainment environment when forwarding coded data. Real-time information flows are encoded, transcoded, compressed, etc. into data streams that may be forwarded to other components within an apparatus or to other apparatuses across a network. In a described implementation, a bitcount accumulation of a data stream is monitored in multiple overlapping windows. The data stream is compared to a data limit in each window of the multiple overlapping windows to determine whether an expected bitcount accumulation has been exceeded. The data stream is modified responsive to the comparison(s). For example, if the bitcount accumulations in each window exceed the expected bit accumulations at the corresponding relative positions of each window, then the bit rate of the data stream can be modified by reducing bit rate consumption.

Dynamic rate control

Adaptive compensation for requantization. A reference picture is decoded. Another copy of the reference picture is then requantized and then decoded. Next, an error picture is calculated and stored. The error picture represents the difference between the reference picture as decoded without requantization and the reference picture as decoded with requantization. The error picture and the requantized reference picture are used to generate a predictive picture that at least partially compensates for generational error introduced by requantization. This compensation for error may be adaptively performed based on system conditions.

Methods and systems for reducing requantization-originated generational error in predictive video streams using motion compensation

A set of known data samples are identified and an approximation of an original function from which the known data samples were obtained is created. The approximation function is then resampled to obtain desired values that are not contained in the set of known data samples.

Method and apparatus for resampling data

Systems and methods for transcoding a video stream. An incoming video stream is spatially transcoded to reduce the bit rate of the video stream. The incoming video stream is decoded and the stream parameters are saved for use in generating the output video stream. The decoded video stream is resampled and the images are spatially reduced. Using the stream parameters of the incoming video stream, an outgoing video stream is generated. Some of the stream parameters are unchanged while others are re-computed for the outgoing video stream.

Spatially transcoding a video stream

A system and method of synchronizing a media stream involves determining urgency measures and favorability measures. An urgency measure relates to a degree by which a media stream is currently out of synchronization. A favorability measure indicates the disruptiveness or likely noticeability altering the media stream at a particular temporal point. As a media stream becomes more and more out of synchronization, the urgency factor increases, and the system looks for places in the media stream at which units such as video frames or audio samples can be added or subtracted to re-achieve synchronization. When the urgency measure is at lower values, the system selects only points in the media stream having relatively high favorability measures. When the urgency measure increases, the system selects points having relatively lower favorability measures.

Media stream synchronization

Method and systems for compressing a video stream with minimal loss after subsampled decoding

Systems and methods for concealing video errors encountered in a frame of a static or moving image that can be used independently or in combination with conventional error concealment techniques, and can be used to conceal an error segment of any shape or location in a frame of a static or moving image. An error segment is identified. A first pixel set adjacent to the error segment and optionally one or more other pixel sets also adjacent to the error segment are selected corresponding the pixel set of the error segment and are flipped toward the error segment. The flipped pixel sets are then selectively weighted. Where only one pixel set is used, the flipped and weighted pixel set replaces the error segment to conceal the error segment. Where more than one pixel set is utilized, the pixel sets are added together to create a sum pixel set that replaces the pixels of the error segment to produce a smooth transition between the error segment and the adjacent, non-corrupt sets of pixels without any distracting boundaries. The smooth transition diminishes the visual impact of the error segment in the frame of the static or moving image.

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Shankar Moni