Method and encoder system for encoding video

Patent metadata

Field	Value
Publication number	US-9866831-B2
Application number	US-201514939590-A
Country	US
Kind code	B2
Filing date	Nov 12, 2015
Priority date	Nov 14, 2014
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

A method for encoding video is disclosed. The method comprises the steps of receiving information representative of pixels in a current digital image frame of a video to be encoded, calculating a group value for each group of neighboring pixels based on the received information, accumulating group values of corresponding groups of pixels in a first sequence of frames to form a first accumulation of accumulated group values, accumulating group values of corresponding groups of pixels in a second sequence of frames to form a second accumulation of accumulated group values, wherein the second sequence includes frames captured over a longer period of time than the first sequence, comparing accumulated group values of the first accumulation with accumulated group values of the second accumulation, calculating a global change value based on the comparison, setting a GOP length based on the global change value; and encoding the current image frame as an intra-frame or inter-frame based on the GOP length. An encoder system for encoding video is also disclosed.

First claim

What is claimed is:

1. A method for encoding video comprising:
receiving information representative of pixels in a current digital image frame of a video to be encoded;
calculating a group value for each group of neighboring pixels based on said received information for groups of neighboring pixels in said current digital image frame;
accumulating group values of corresponding groups of neighboring pixels in a first sequence of digital image frames comprising said current frame and a first number of preceding image frames to form a first accumulation of accumulated group values;
accumulating group values of corresponding groups of neighboring pixels in a second sequence of digital image frames comprising said current digital image frame and a second number of preceding digital image frames to form a second accumulation of accumulated group values, wherein said second sequence of digital image frames includes digital image frames captured over a longer period of time than the image frames of said first sequence;
comparing accumulated group values of said first accumulation with accumulated group values of corresponding groups of neighboring pixels in said second accumulation;
calculating a global change value based on the comparison of the first and second accumulations of group values;
setting a GOP length as a number of frames to be encoded in a group of pictures based on said global change value, including making a choice between increasing, decreasing, and leaving unaltered a current GOP length; and
encoding said current image frame as an intra-frame or inter-frame based on said GOP length.

2. The method according to claim 1 , wherein calculating the global change value comprises calculating a change value for each group of neighboring pixels based on a difference between corresponding accumulated group values of said first and second accumulations.

3. The method according to claim 1 , further comprising:
comparing said global change value to a high threshold value; and
if said global change value is above said high threshold value, decreasing said GOP length from a current GOP length.

4. The method according to claim 3 , wherein said high threshold value corresponds to a global change value representing motion of an object of interest in a scene captured in said current image frame.

5. The method according to claim 1 , further comprising:
comparing said global change value to a low threshold value; and
if said global change value is below said low threshold value, increasing said GOP length from a current GOP length.

6. The method according to claim 5 , wherein said low threshold value corresponds to a global change value representing substantially no motion in a scene captured in said current image frame.

7. The method according to claim 1 , further comprising:
limiting said GOP length to a predetermined GOP range defined by a maximum allowable GOP length and a minimum allowable GOP length.

8. The method according to claim 1 , further comprising:
comparing said global change value to a high threshold value;
if said global change value is above said high threshold value, decreasing said GOP length from a current GOP length;
comparing said global change value to a global change limit, wherein the global change limit is a threshold that is of a higher value than said high threshold; and
if said global change value is above said global change limit, encoding said current image frame as an intra-frame independent of the GOP length.

9. The method according to claim 8 , wherein said global change limit corresponds to a global change value representing a substantial scene change in a scene captured in said current image frame.

10. The method according to claim 1 , wherein said accumulation of group values comprises adding group values of corresponding groups of pixels in said first sequence of digital image frames and second sequence of digital image frames, respectively.

11. The method according to claim 1 , wherein each group of neighboring pixels consists of a number of pixels which is equal to a number of pixels in macro blocks used in the step of encoding.

12. An encoder system for encoding video comprising:
a receiving module arranged to receive information representative of pixels in a current digital image frame of a video to be encoded;
a group value module arranged to calculate a group value for each group of neighboring pixels based on said received information for groups of neighboring pixels in said current digital image frame;
an accumulation module arranged to accumulate group values of corresponding groups of neighboring pixels in a first sequence of digital image frames comprising said current image frame and a first number of preceding image frames to form a first accumulation of accumulated group values, and arranged to accumulate group values of corresponding groups of neighboring pixels in a second sequence of digital image frames comprising said current image frame and a second number of preceding image frames to form a second accumulation of accumulated group values, said second sequence of digital image frames includes digital image frames captured over a longer period of time than the image frames of said first sequence;
a comparing module arranged to compare accumulated group values of said first accumulation with accumulated group values of corresponding groups of neighboring pixels of said second accumulation;
a global change value module arranged to calculate a global change value based on the comparison of the first and second accumulations of group values;
a GOP length module arranged to set a GOP length as a number of frames to be encoded in a group of pictures based on said global change value, including making a choice between increasing, decreasing, and leaving unaltered a current GOP length; and
an encoding module arranged to encode said current image frame as an intra-frame or an inter-frame based on said GOP length.

13. A camera comprising an encoder system, the encoder system comprising:
a receiving module arranged to receive information representative of pixels in a current digital image frame of a video to be encoded;
a group value module arranged to calculate a group value for each group of neighboring pixels based on said received information for groups of neighboring pixels in said current digital image frame;
an accumulation module arranged to accumulate group values of corresponding groups of neighboring pixels in a first sequence of digital image frames comprising said current image frame and a first number of preceding image frames to form a first accumulation of accumulated group values, and arranged to accumulate group values of corresponding groups of neighboring pixels in a second sequence of digital image frames comprising said current image frame and a second number of preceding image frames to form a second accumulation of accumulated group values, said second sequence of digital image frames includes digital image frames captured over a longer period of time than the image frames of said first sequence;
a comparing module arranged to compare accumulated group values of said first accumulation with accumulated group values of corresponding groups of neighboring pixels of said second accumulation;
a global change value module arranged to calculate a global change value based on the comparison of the first and second accumulations of group values;
a GOP length module arranged to set a GOP length as a number of frames to be encoded in a group of pictures based on said global change value, including making a choice between increasing, decreasing, and leaving unaltered a current

Assignees

• Axis Ab

Inventors

• Fan Xing Danielsson
• Edpalm Viktor
• Pihl Fredrik
• Persson Lars
• Martins Alexandre

Classifications

• H04N19/177

  the unit being a group of pictures [GOP] · CPC title

• H04N19/503

  involving temporal prediction (adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109) · CPC title

• H04N19/114

  Adapting the group of pictures [GOP] structure, e.g. number of B-frames between two anchor frames (H04N19/107 takes precedence) · CPC title

• H04N19/593

  involving spatial prediction techniques · CPC title

• H04N19/87

  involving scene cut or scene change detection in combination with video compression · CPC title