Adaptive interpolation filters for video coding

Patent metadata

Field	Value
Publication number	US-10506252-B2
Application number	US-201615372686-A
Country	US
Kind code	B2
Filing date	Dec 8, 2016
Priority date	Jan 9, 2007
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

In digital video image encoding and decoding, a filter type is selected based on symmetrical properties of the images and coefficient values of an interpolation filter are calculated based on the selected filter type. Coefficient values, filter tap-length and selected filter-type are provided in the encoded video data. Coefficient values are also calculated based on a prediction signal representative of the difference between a video frame and a reference image. The prediction signal is calculated from the reference image based on a predefined base filter and motion estimation performed on the video frame. The predefined base filter has fixed coefficient values. Coefficient values are selected from interpolation of pixel values in a selected image segment in the video frame. Symmetry properties of images can be a vertical symmetry, a horizontal symmetry and a combination thereof, so that only a portion of the filter coefficients are coded.

First claim

The invention claimed is:

1. A method for encoding images in a digital video sequence, comprising:
based on symmetry of statistical properties of the images in the digital video sequence, selecting an interpolation filter used in motion compensated prediction from the group consisting of:
a first filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in both the horizontal and vertical directions;
a second filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the horizontal direction;
a third filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the vertical direction;
a fourth filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the horizontal direction, and in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the vertical direction; and
a non-symmetrical filter type;

calculating coefficient values for the selected interpolation filter based on a minimization of energy of a prediction error signal; and
providing encoded data indicative of the digital video sequence for communication to a video decoder, the encoded data comprising information indicating:
the selected filter type for the interpolation filter;
the calculated coefficient values for the interpolation filter; and
a tap length indicating a number of the coefficient values of the interpolation filter.

2. The method of claim 1 , wherein the digital video sequence comprises a sequence of video frames;
and wherein the prediction error signal is representative of a difference between a selected one of the video frames and a reference image.

3. The method of claim 1 , wherein the digital video sequence comprises a sequence of video frames;
and wherein each video frame of the sequence of video frames is partitioned in a plurality of sections, at least one section of the plurality of sections having a different symmetry property from other sections of the plurality of sections.

4. The method of claim 3 , wherein the interpolation filter comprises a filter for the at least one section and one or more other filters for the other sections.

5. An apparatus for encoding images in a digital video sequence, the apparatus comprising:
at least one processor; and
at least one memory including computer program code, the at least one memory and the computer program code configured to, with the processor, cause the apparatus at least to:
based on symmetry of statistical properties the images in the digital video sequence, select an interpolation filter used in motion compensated prediction from the group consisting of:
a first filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in both the horizontal and vertical directions;
a second filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the horizontal direction;
a third filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the vertical direction;
a fourth filter type in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the horizontal direction, and in which the same filter coefficients are used for the same distances of full-pixel positions to sub-pixel positions in the vertical direction; and
a non-symmetrical filter type;

calculate coefficient values for the selected interpolation filter based on a minimization of energy of a prediction error signal; and
provide encoded data indicative of the digital video sequence for communication to a video decoder, the encoded data including information indicating:
the selected filter type for the interpolation filter;
the calculated coefficient values for the interpolation filter; and
a tap length indicating a number of the coefficient values of the interpolation filter.

6. The apparatus of claim 5 , wherein the digital video sequence comprises a sequence of video frames;
and wherein the prediction error signal is representative of a difference between a selected one of the video frames and a reference image.

7. The apparatus of claim 5 , wherein the digital video sequence comprises a sequence of video frames;
and wherein each video frame of the sequence of video frames is partitioned in a plurality of sections, at least one section of the plurality of sections having a different symmetry property from other sections of the plurality of sections.

8. The apparatus of claim 7 , wherein the interpolation filter comprises a filter for the at least one section and one or more other filters for the other sections.

Assignees

• Conversant Wireless Licensing Sarl

Inventors

• Rusanovskyy Dmytro
• Ugur Kemal

Classifications

• H04N19/136

  Incoming video signal characteristics or properties · CPC title

• H04N19/42

  characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation (H04N19/635 takes precedence) · CPC title

• H04N7/12

  Systems in which the television signal is transmitted via one channel or a plurality of parallel channels, the bandwidth of each channel being less than the bandwidth of the television signal (H04N7/24 takes precedence) · CPC title

• H04N19/523 Primary

  with sub-pixel accuracy · CPC title

• H04N19/63

  using sub-band based transform, e.g. wavelets · CPC title