VIDEO FRAME ENCODING AND DECODING

• US 20090080521A1
• Filed: 11/26/2008
• Published: 03/26/2009
• Est. Priority Date: 01/30/2004
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Wiegand, Thomas, Schwarz, Heiko, MARPE, Detlev
• Granted Patent: US 7,760,806 B2
• Time in Patent Office: Days
• US Class Current: 375/240.120
• CPC Class Codes: H04N 19/112 according to a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/16 for a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/174 the region being a slice, e.g. a line of blocks or a group of blocks
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A video frame arithmetical context adaptive encoding and decoding scheme is presented which is based on the finding, that, for sake of a better definition of neighborhood between blocks of picture samples, i.e. the neighboring block which the syntax element to be coded or decoded relates to and the current block based on the attribute of which the assignment of a context model is conducted, and when the neighboring block lies beyond the borders or circumference of the current macroblock containing the current block, it is important to make the determination of the macroblock containing the neighboring block dependent upon as to whether the current macroblock pair region containing the current block is of a first or a second distribution type, i.e., frame or field coded.

Claims

1. A method for encoding a video signal representing at least one video frame, with at least one video frame being composed of picture samples, the picture samples belonging either to a first or a second field being captured at different time instants, the video frame being spatially divided up into macroblock pair regions, each macroblock pair region being associated with a top and bottom macroblock, the method comprising the following steps:

deciding, for each macroblock pair region, as to whether same is of a first or a second distribution type;

assigning, for each macroblock pair region, each of the pixel samples in the respective macroblock pair region to a respective one of the top and bottom macroblock of the respective macroblock pair region, in accordance with the distribution type of the respective macroblock pair region;

pre-coding the video signal into a pre-coded video signal, the pre-coding comprising the sub-step of pre-coding a current macroblock of the top and bottom macroblock associated with a current macroblock pair region of the macroblock pair regions to obtain a current syntax element being a type indicator specifying a partitioning of the current macroblock used for motion description;

determining, for the current syntax element, a neighboring macroblock at least based upon as to whether the current macroblock pair region is of a first or second distribution type;

assigning one of at least two context models to the current syntax element based on a type indicator of the neighboring macroblock, wherein each context model is associated with a different probability estimation; and

arithmetically encoding the syntax element into a coded bit stream based on the probability estimation with which the assigned context model is associated.

2. The method in accordance with claim 1, wherein the step of determining is further dependent on as to whether the current macroblock is the top or the bottom macroblock of the current macroblock pair region.

3. The method in accordance with claim 1, wherein the step of pre-coding further comprises the step of pre-coding the reference sub-part to obtain a reference syntax element as the predetermined attribute.

4. The method in accordance with claim 1, wherein the step of determining is performed twice in order to obtain a neighboring macroblock to the top and a neighboring macroblock to the left of the current macroblock and the step of assigning one of at least two context models is based on a pre-determined attribute of both the neighboring macroblock to the top and the neighboring macroblock to the left of the current macroblock.

12. The method in accordance with claim 1, wherein the step of determining is performed twice in order to obtain a neighboring macroblock to the top and a neighboring macroblock to the left of the predetermined macroblock and the step of assigning one of at least two context models is based on a pre-determined attribute of both the neighboring macroblock to the top and the neighboring macroblock to the left of the predetermined macroblock.

5. A method for decoding a predetermined syntax element from a coded bit stream, the coded bit stream being an arithmetically encoded version of a pre-coded video signal, the pre-coded video signal being a pre-coded version of a video signal, the video signal representing at least one video frame being composed of picture samples, the picture samples belonging either to a first or a second field being captured at a different time instants, the video frame being spatially divided up into macroblock pair regions, each macroblock pair region being associated with a top and a bottom macroblock, each macroblock pair region being either of a first or a second distribution type, wherein, for each macroblock pair region, each of the pixel samples in the respective macroblock pair region is assigned to a respective one of the top and bottom macroblock of the respective macroblock pair region in accordance with the distribution type of the respective macroblock pair region, wherein the predetermined syntax element relates to a predetermined macroblock of the top and bottom macroblock of a predetermined macroblock pair region of the macroblock pair regions and is a type indicator specifying a partitioning of the predetermined macroblock used for motion description, wherein the method comprises the following steps:

determining, for the predetermined syntax element, a neighboring macroblock at least based upon as to whether the predetermined macroblock pair region is of a first or a second distribution type;

assigning one of at least two context models to the predetermined syntax element based on a type indicator of the neighboring macroblock, wherein each context model is associated with a different probability estimation; and

arithmetically decoding the predetermined syntax element from the coded bit stream based on the probability estimation with which the assigned context model is associated.

6. The method in accordance with claim 5, wherein the step of determining is performed among a set comprising the other macroblock of the top and bottom macroblock of the predetermined macroblock pair region, the top macroblock of a macroblock pair region adjacent to the predetermined macroblock pair region and the bottom macroblock of the macroblock pair region adjacent to the predetermined macroblock pair region.

7. The method in accordance with claim 5, wherein the step of determining is performed among a set comprising at least one of a top and a bottom macroblock of a macroblock pair region adjacent to the predetermined macroblock pair region, and is further dependent on as to whether the macroblock pair region adjacent to the predetermined macroblock pair region is of the first or the second distribution type.

8. Method in accordance with claim 5, wherein the assignment of the pixel samples is such that, in accordance with the first distribution type, pixel samples lying in an upper part of the respective macroblock pair region are assigned to the top macroblock and pixel samples lying in a lower part of the respective macroblock pair region are assigned to the bottom macroblock, whereas, in accordance with the second distribution type, pixel samples in the respective macroblock pair region belonging to the first field are assigned to the top macroblock and pixel samples in the respective macroblock pair region belonging to the second field are assigned to the bottom macroblock.

9. The methods in accordance with claim 8, wherein the pixel samples belonging to the first field and the pixel samples belonging to the second field are interlaced row-wise so that pixel samples assigned to the top and bottom macroblock of a respective macroblock pair region in accordance with the first distribution type have a greater pitch in row direction than pixel samples assigned to the top and bottom macroblock of a respective macroblock pair region in accordance with the second distribution type.

10. The method in accordance with claim 5, wherein the step of determining is further dependent on as to whether the predetermined macroblock is the top or the bottom macroblock of the predetermined macroblock pair region.

11. Method in accordance with claim 5, wherein the step of arithmetically decoding comprises:

binary arithmetically decoding a sequence of the binary decisions belonging to the predetermined syntax element, wherein, at least for a predetermined part of the binary decisions, the decoding is based on the probability estimation with which the assigned context model is associated; and

reconstructing the syntax element from the sequence of binary decisions.

15. Method according to claim 5, wherein the step of assigning one of at least two context models is performed such that the assignment is based on

an availability of the neighboring macroblock indicating as to whether the predetermined macroblock and the neighboring macroblock belong to the same slice of the video frame or to different slices of the video frame.

16. Method according to claim 9, wherein the step of determining is performed such that the neighboring macroblock belongs to a macroblock pair region to the left of the predetermined macroblock pair region of predetermined macroblock and the determination results in a selection among the top and bottom macroblock of macroblock pair region to the left of the predetermined macroblock pair region that is effectively dependent on

the predetermined macroblock pair region being of the first or second distribution type,

the macroblock pair region to the left being of the first or second distribution type, and

the predetermined macroblock being the top or bottom macroblock of the predetermined macroblock pair region.

13. An Apparatus for encoding a video signal representing at least one video frame, with at least one video frame being composed of picture samples, the picture samples belonging either to a first or a second field being captured at different time instants, the video frame being spatially divided up into macroblock pair regions, each macroblock pair region being associated with a top and bottom macroblock, the apparatus comprising

means for deciding, for each macroblock pair region, as to whether same is of a first or a second distribution type;

means for assigning, for each macroblock pair region, each of the pixel samples in the respective macroblock pair region to a respective one of the top and bottom macroblock of the respective macroblock pair region, in accordance with the distribution type of the respective macroblock pair region;

means for pre-coding the video signal into a pre-coded video signal, the pre-coding comprising the sub-step of pre-coding a current macroblock of the top and bottom macroblock associated with a current macroblock pair region of the macroblock pair regions to obtain a current syntax element being a type indicator specifying a partitioning of the current macroblock used for motion description;

means for determining, for the current syntax element, a neighboring macroblock at least based upon as to whether the current macroblock pair region is of a first or second distribution type;

means for assigning one of at least two context models to the current syntax element based on a type indicator of the neighboring macroblock, wherein each context model is associated with a different probability estimation; and

means for arithmetically encoding the syntax element into a coded bit stream based on the probability estimation with which the assigned context model is associated.

14. An apparatus for decoding a predetermined syntax element from a coded bit stream, the coded bit stream being an arithmetically encoded version of a pre-coded video signal, the pre-coded video signal being a pre-coded version of a video signal, the video signal representing at least one video frame being composed of picture samples, the picture samples belonging either to a first or a second field being captured at a different time instants, the video frame being spatially divided up into macroblock pair regions, each macroblock pair region being associated with a top and a bottom macroblock, each macroblock pair region being either of a first or a second distribution type, wherein, for each macroblock pair region, each of the pixel samples in the respective macroblock pair region is assigned to a respective one of the, top and bottom macroblock of the respective macroblock pair region in accordance with the distribution type of the respective macroblock pair region, wherein the predetermined syntax element relates to a predetermined macroblock of the top and bottom macroblock of a predetermined macroblock pair region of the macroblock pair regions and is a type indicator specifying a partitioning of the predetermined macroblock used for motion description, wherein the apparatus comprises

means for determining, for the predetermined syntax element, a neighboring macroblock at least based upon as to whether the predetermined macroblock pair region is of a first or a second distribution type;

means for assigning one of at least two context models to the predetermined syntax element based on a type indicator of the neighboring macroblock, wherein each context model is associated with a different probability estimation; and

means for arithmetically decoding the predetermined syntax element from the coded bit stream based on the probability estimation with which the assigned context model is associated.