Signaling reference frame distances

• US 20050111547A1
• Filed: 11/15/2004
• Published: 05/26/2005
• Est. Priority Date: 09/07/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Lin, Chih-Lung, Holcomb, Thomas W., Mukerjee, Kunal
• Granted Patent: US 8,085,844 B2
• Time in Patent Office: Days
• US Class Current: 375/240.30
• CPC Class Codes: H04N 19/112 according to a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/517 by encoding
• CPC Class Codes: H04N 19/573 Motion compensation with multiple frame prediction using two or more reference frames in a given prediction direction
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Techniques and tools for signaling reference frame distances are described. For example, a video encoder signals a code for a reference frame distance for a current field-coded interlaced video frame. The code indicates a count of frames (e.g., bi-directionally predicted frames) between the current frame and a preceding reference frame. The code may be a variable length code signaled in the frame header for the current frame. The encoder may selectively signal the use of a default value for reference frame distances rather than signal a reference frame distance per frame. A video decoder performs corresponding parsing and decoding.

Claims

1. A method comprising:

processing a code for a reference frame distance for a current field-coded interlaced video frame, wherein the code indicates a count of frames between the current field-coded interlaced video frame and a preceding reference frame.

2. The method of claim 1 wherein the count is a count of bi-directionally predicted field-coded interlaced video frames between the current field-coded interlaced video frame and the preceding reference frame.

3. The method of claim 1 wherein the count is an arbitrary value selected so as to improve performance of operations that are based at least in part upon the count.

4. The method of claim 3 wherein the operations are motion vector scaling operations for motion vector prediction.

5. The method of claim 1 wherein the code is signaled in a frame header for the current field-coded interlaced video frame.

6. The method of claim 1 wherein the code is a variable length code.

7. The method of claim 1 wherein the current field-coded interlaced video frame is an I/I, I/P, P/I, or P/P frame.

8. The method of claim 1 wherein the current field-coded interlaced video frame includes at least one interlaced P-field.

9. The method of claim 1 wherein the processing includes encoding, the method further comprising signaling the code in a coded video bitstream.

10. The method of claim 1 wherein the processing includes decoding, the method further comprising, before the decoding, parsing the code from a coded video bitstream.

11. A method comprising:

processing a first syntax element that indicates whether reference frame distances for plural frames are signaled or have a default value; and

for each of the plural frames,

if reference frame distances are signaled then processing a second syntax element per frame that indicates a reference frame distance for the frame, and

if reference frame distances have the default value then using the default value for the reference frame distance for the frame.

12. The method of claim 11 wherein, for each of the plural frames, the reference frame distance for the frame indicates a count of bi-directionally predicted frames between the frame and a preceding reference frame.

13. The method of claim 11 wherein, for each of the plural frames, the reference frame distance for the frame is an arbitrary value selected so as to improve performance of operations that are based at least in part upon the reference frame distance.

14. The method of claim 11 wherein each of the plural frames is a field-coded interlaced video frame that is not bi-directionally predicted.

15. The method of claim 11 wherein the first syntax element is part of an entry point header for an entry point segment that includes the plural frames.

16. The method of claim 11 wherein, if reference frame distances are signaled, the second syntax element per frame is part of a frame header for the frame.

17. The method of claim 11 wherein, if reference frame distances are signaled, the second syntax element per frame is a variable length code.

18. The method of claim 11 wherein the default value is zero.

19. The method of claim 11 wherein the processing occurs during encoding, the method further comprising:

signaling the first syntax element in a coded video bitstream; and

for each of the plural frames, if reference frame distances are signaled, signaling the second syntax element per frame in the coded video bitstream.

20. The method of claim 11 wherein the processing occurs during decoding, the method further comprising:

parsing the first syntax element from a coded video bitstream; and

for each of the plural frames, if reference frame distances are signaled, parsing the second syntax element per frame from the coded video bitstream.

21. A decoder comprising:

means for buffering a coded video bitstream; and

means for decoding a variable length code for a reference frame distance for a current frame, wherein the variable length code indicates a count of bi-directionally predicted frames between the current frame and a preceding reference frame.

22. The decoder of claim 21 wherein the variable length code is signaled in a frame header for the current frame.

23. The decoder of claim 21 further comprising means for scaling motion vectors based at least in part upon the reference frame distance.