Motion Prediction In Video Coding
Patent No. US11805267 (titled "Motion Prediction In Video Coding") was filed by Nokia Technologies Oy on May 24, 2021.
What is this patent about?
’267 is related to the field of video coding and, more specifically, to improving the efficiency of motion-compensated prediction in video codecs. Modern video codecs use techniques like motion compensation to reduce the amount of data needed to represent video, by predicting pixel values in a frame based on previously encoded frames. This involves finding similar areas in reference frames and encoding only the differences, along with motion vectors indicating the displacement.
The underlying idea behind ’267 is to reduce rounding errors that accumulate during bi-directional or multi-directional prediction. Instead of rounding each prediction signal individually before combining them, the patent proposes maintaining the prediction signals at a higher precision throughout the calculation. Only after the predictions are combined is the precision reduced to the original level, thereby minimizing the impact of rounding errors on the final prediction.
The claims of ’267 focus on a method and apparatus for encoding and decoding video. For a given block of pixels, the method involves determining two or more reference blocks using motion vectors. Each reference block is used to generate a prediction with a higher precision than the original pixel values. These predictions are then combined, and the precision of the combined prediction is reduced by bit-shifting , effectively rounding the result to the original precision.
In practice, the invention involves using interpolation filters to obtain prediction values from reference blocks. These filters operate on pixel values in the reference blocks to estimate values at fractional pixel locations, allowing for more accurate motion compensation. The key is that the intermediate results of these filtering operations, as well as the subsequent combination of predictions, are performed using a higher bit depth (i.e., higher precision) than the original video data. This reduces the quantization noise introduced by rounding at each stage.
This approach differs from prior methods that might round each prediction signal before combining them, or that might signal rounding offsets in the bitstream. By maintaining higher precision throughout the prediction calculation, ’267 avoids the need to signal rounding direction and reduces the accumulation of rounding errors, leading to improved coding efficiency without significantly increasing decoder complexity. The final bit-shift operation ensures that the output prediction has the same precision as the original video signal.
How does this patent fit in bigger picture?
Technical landscape at the time
In the early 2010s when ’267 was filed, video codecs commonly employed hybrid encoding schemes, at a time when motion compensation was typically implemented using block-based prediction. Inter prediction methods using image information from previous or later images and Intra prediction methods using image information within the same image were both prevalent. Hardware constraints made maintaining high precision throughout the prediction process non-trivial, often requiring trade-offs between computational complexity and coding efficiency.
Novelty and Inventive Step
The application was subject to a non-final rejection based on obviousness-type double patenting. Claims 1, 7, 13, 19, 25 and 31 were provisionally rejected as being unpatentable over claim 1 of U.S. Patent No. 11,019,354 and U.S. Patent No. 10,523,960. The prosecution record does not describe the technical reasoning or specific claim changes that led to allowance.
Claims
This patent contains 36 claims, with independent claims numbered 1, 7, 13, 19, 25, and 31. The independent claims are generally directed to methods, apparatuses, and computer program products for encoding and decoding blocks of pixels using motion vectors and precision adjustments. The dependent claims generally elaborate on specific aspects and implementations of the methods, apparatuses, and computer program products described in the independent claims.
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Description
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US11805267
- Application Number
- US17328750
- Filing Date
- May 24, 2021
- Status
- Granted
- Expiry Date
- Jan 6, 2032
- External Links
- Slate, USPTO, Google Patents