Dynamic GOP system and method for digital video encoding

• US 6,959,044 B1
• Filed: 08/21/2001
• Issued: 10/25/2005
• Est. Priority Date: 08/21/2001
• Status: Expired due to Fees

• Current Assignee: Cisco Systems Canada Co. (Cisco Systems, Inc.)
• Original Assignee: Cisco Systems Canada Co. (Cisco Systems, Inc.)
• Inventors: Cote, Guy, Jin, Luojun, Winger, Lowell
• Primary Examiner(s): DIEP, NHON THANH
• Application Number:
  US09/935,140
• Time in Patent Office: 1,526 Days
• Field of Search: H04/N00.7/12, 348/699, 348/700, 348/701, 348/412.1, 348/415.1, 348/722, 382/173, 382/195, 382/280, 375/240.12
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/114 Adapting the group of pictures [GOP] structure, e.g. number of B-frames between two anchor frames H04N19/107 takes precedence
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/87 involving scene cut or scene change detection in combination with video compression

Abstract

This invention discloses an intra-frame complexity based dynamic GOP system and method for the encoding of MPEG-2 video streams. The present invention may be used as a rate control tool to improve video quality. The selective insertion of low complexity I frames in scene changes such as fades is disclosed. It is disclosed that the selective use of I frames in certain scene change situations can improve encoder performance, particularly when encoding at a low bit rate.

Claims

1. An MPEG video encoder, said encoder comprising:

a) means for analyzing statistics from a video stream;

b) means for analyzing statistics, for determining if a scene change has occurred; and

c) means for creating a modified video stream, wherein a frame with low complexity is selected as an I frame in the modified video stream if the scene change is a fade.

2. The encoder of claim 1 wherein said means for analyzing statistics further comprises means for calculating the global complexity of a current frame within said video stream.

3. The encoder of claim 2, wherein the means for creating a modified video stream codes said current frame as an I frame and codes the frame previous to said current frame as a P frame in said modified video stream, if a scene change has occurred and if said scene change is a scene cut.

4. The encoder of claim 2, wherein the means to create a modified video stream codes said current frame as a B frame in said modified video stream if a scene change has occurred and said scene change is a dissolve.

5. The encoder of claim 2, wherein the means to create a modified video stream codes a frame with the lowest complexity in a fade as a I frame in said modified video stream if a scene change has occurred and said scene change is a fade.

6. A method for creating a modified video stream, the method comprising:

analyzing a video stream comprising a plurality of I, B, and P frames;

determining when a scene change has occurred;

creating a modified video steam, wherein a frame with low complexity is selected as an I frame in the modified video stream if the scene change is a fade.

7. The method of claim 6 wherein if a scene cut has occurred, at a current frame, coding said current frame as an I frame and coding the frame previous to said current frame as P frame in said modified video stream.

8. The method of claim 6 wherein if a dissolve has occurred, at a current frame, coding said current frame as a B frame in said modified video stream.

9. The method of claim 6 wherein if a fade has occurred, selecting a frame with low complexity in the fade as an I frame in said modified video stream.

10. A computer readable medium including instructions for creating a modified video stream, said instructions comprising:

computer code for analyzing the frames of an input video stream to determine when a scene change has occurred;

computer code for creating a modified video stream, wherein a frame with low complexity is selected as an I frame in the modified video stream if the scene change is a fade.

11. The medium of claim 10 wherein if a scene cut has occurred at a current frame, coding said current frame as an I frame and the frame previous to said current frame as a P frame, in said modified video stream.

12. The medium of claim 11 wherein if a dissolve has occurred at a current frame, coding said current frame as a B frame in said modified video stream.

13. The medium of claim 12 wherein if a fade has occurred, selecting a frame with the lowest-complexity in the fade as an I frame in said modified video stream.

14. A method for improving encoder performance, said method determining if a fade has occurred in a video stream, if a fade has occurred, modifying said video stream by selecting a frame with the lowest complexity in the fade as an I frame in said video stream.

15. A system for improving encoder performance, said system having detection means to determine if a fade has occurred in a video stream, if a fade has occurred, utilizing means to select a frame with low complexity in the fade as an I frame in said video stream.

16. An MPEG video encoder, said encoder comprising:

a) a statistical analysis module for analyzing statistics from a video stream;

b) a scene change analysis module connected to said statistical analysis module for determining if a scene change has occurred; and

c) a modification module to create a modified video stream, wherein a frame with low complexity is selected as an I frame in the modified video stream if the scene change is a fade.

17. The encoder of claim 16 wherein said statistical analysis module calculates the global complexity of a current frame within said video stream.

18. The encoder of claim 17, wherein said modification module codes said current frame as an I frame and codes the frame previous to said current frame as P frame in said modified video steam, if a scene change has occurred and if the scene change is a cut.

19. The encoder of claim 17, wherein said modification module codes said cent frame as a B frame in said modified video stream, if a scene change has occurred and if the scene change is a dissolve.

20. The encoder of claim 17, wherein said modification module codes a frame with the lowest complexity in a fade as an I frame in said modified video stream, if a scene change has occurred and if the scene change is a fade.