Method for dynamic 3D wavelet transform for video compression

• US 6,801,573 B2
• Filed: 12/21/2000
• Issued: 10/05/2004
• Est. Priority Date: 12/21/2000
• Status: Active Grant

• Current Assignee: Ohio State Innovation Foundation (Ohio State University)
• Original Assignee: Ohio State University
• Inventors: Zheng, Yuan F.
• Primary Examiner(s): Vo, Tung T.
• Application Number:
  US09/746,334
• Publication Number:
  US 20020101929A1
• Time in Patent Office: 1,384 Days
• Field of Search: H04/B.166, G06/K.930, 375/240.01, 375/240.09, 375/240.1, 375/240.11, 375/240.13, 375/240.14, 375/240.15, 375/240.16, 375/240.17, 375/240.21, 348/409.1, 348/410.1, 348/411.1, 348/412.1, 348/415.1, 382/239, 382/240
• US Class Current: 375/240.11
• 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 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/1883 the unit relating to sub-band structure, e.g. hierarchical level, directional tree, e.g. low-high [LH], high-low [HL], high-high [HH]
• CPC Class Codes: H04N 19/62 by frequency transforming in three dimensions H04N19/63 takes precedence
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets

Abstract

A dynamic 3D wavelet transform system and method for compressing video including color or black and white signal. The method applies a so-called packed integer wavelet transform to individual video frames to generate wavelet coefficients in the spatial domain (x and y directions). The generated wavelet coefficients are compared to determine if a new frame is similar in content with the previous frame. All the similar frames are grouped together for performing the wavelet transform in the temporal domain (t direction). A frame with different content will start a new group until another different frame is reached. The comparison is based on the information of the Low-Low (LL) band in the output of the wavelet transform of each frame instead of the entire frame. The coefficients generated by the wavelet transform in the spatial domain are quantized before the wavelet transform in the temporal domain is applied to them The methods allow a hybrid 2D and 3D compression. The 2D wavelet transform is first performed on each frame to obtain the LL, LH, HL, and HH bands. The wavelet transform is further applied in the temporal domain in the LL band only. Compression is achieved based on the 2D wavelet transform in the LH, HL, and HH bands, and 3D wavelet transform in the LL band. Using the LL band reduces the operation space and computation time for the wavelet transform while still achieving a high compression ratio because the wavelet coefficients in the LH, HL, and HH bands are sparse.

Claims

1. A method for real-time compression of video data comprising the steps of:

(a) applying 2D wavelet transform to each video frame to generate LL, LH, HL, and HH bands;

(b) applying 2D wavelet transform to each video frame in the LL band to create LL, LH, HL, and HH subbands;

(c) within each LL band or subband,

(i) comparing a current video frame to a next video frame to compute a difference between the frames;

(ii) assigning the current video frame to a current group if the difference is less than or equal to a threshold;

(iii) assigning the current video frame to a new group if the difference is greater than the threshold;

(d) quantizing the wavelet coefficients from the LH, HL, and HH bands resulting from step (a);

(e) quantizing the wavelet coefficients from the LL subband resulting from step (b);

(f) applying wavelet transform in the temporal domain to the quantized wavelet coefficients resulting from step (e);

(g) quantizing the wavelet coefficients resulting from step (f);

(h) encoding the quantized wavelet coefficients resulting from step (d);

(i) encoding the quantized wavelet coefficients resulting from step (g);

(j) outputting the encoded quantized wavelet coefficients from steps (h) and (i).

2. The method of claim 1 wherein the step of applying 2D wavelet transform to each video frame and band to generate LL, LH, HL, and HH bands and subbands comprises the step of applying integer-based wavelet transform to each video frame or band.

3. The method of claim 2 wherein the step of applying integer-based wavelet transform comprises the step of applying a packed computation method to the integer-based wavelet transform.

4. The method of claim 1 wherein the step of comparing a current video frame to a next video frame to compute a difference between the frames comprises the step of comparing the value of the wavelet coefficients of the LL bands or subbands.

5. The method of claim 1 further comprising the step of applying 2D wavelet transform to the LL subband of each frame after step (c).

6. The method of claim 1 further comprising the steps of:

(k) decoding the encoded quantized wavelet coefficients of the plurality of frame groups;

(l) decoding the encoded quantized wavelet coefficients of the LH, HL, and HH bands;

(m) dequantizing wavelet coefficients in the plurality of frame groups;

(n) dequantizing wavelet coefficients in the LH, HL, and HH bands;

(o) applying an inverse wavelet transform in the temporal domain of the LL bands;

(p) applying an inverse wavelet transform in the spatial domain of the LL, LH, HL, and HH bands; and

(q) outputting decompressed video data resulting from steps (p).

7. A method for real-time compression of video data comprising the steps of:

(a) applying 2D wavelet transform to each video frame to generate LL, LH, HL, and HH bands;

(b) within the LL band,

(i) comparing a current video frame to a next video frame to compute a difference between the frames;

(ii) assigning the current video frame to a current group if the difference is less than or equal to a threshold;

(iii) assigning the current video frame to a new group if the difference is greater than the threshold;

(c) for each group created in accordance with step (b), applying 3D wavelet transform to the LL band of all the frames in the group;

(d) quantizing the wavelet coefficients resulting from step (c);

(e) encoding the quantized wavelet coefficients resulting from step (d);

(f) quantizing the wavelet coefficients from the LH, HL, and HH bands;

(g) encoding the quantized wavelet coefficients resulting from step (f); and

(h) outputting the encoded quantized wavelet coefficients from steps (e) and (g).

8. The method of claim 7 wherein the step of applying 2D wavelet transform to each video frame to generate LL, LH, HL, and HH bands comprises the step of applying integer-based wavelet transform to each video frame.

9. The method of claim 8 wherein the step of applying integer-based wavelet transform comprises the step of applying a packed computation method to the integer-based wavelet transform.

10. The method of claim 7 wherein the step of quantizing wavelet coefficients in step (c) comprises the step of quantizing wavelet coefficients in accordance with the adaptive dead zone method.

11. The method of claim 7 wherein the steps of encoding the quantized wavelet coefficients from steps (e) and (g) comprises the step of stack run encoding the wavelet coefficients.

12. The method of claim 7 further comprising the steps of:

(i) decoding the encoded quantized wavelet coefficients of the plurality of frame groups of the LL band;

(j) decoding the encoded quantized wavelet coefficients of the LH, HL, and HH bands;

(k) dequantizing wavelet coefficients in the LH, HL, and HH bands;

(l) dequantizing wavelet coefficients in the plurality of frame groups of the LL band;

(m) applying an inverse wavelet transform in the temporal domain of the LL subband;

(n) applying an inverse wavelet transform in the spatial domain of the LL, LH, HL, and HH bands; and

(o) outputting decompressed video data resulting from step (n).

13. A method decompressing video data comprising the steps of:

(a) decoding the encoded quantized wavelet coefficients of a plurality of frame groups of the LL band;

(b) dequantizing quantized wavelet coefficients in the plurality of frame groups of the LL band;

(c) decoding the encoded quantized wavelet coefficients of LH, HL, and HH bands;

(d) dequantizing quantized wavelet coefficients in the LH, HL, and HH bands;

(e) applying an inverse wavelet transform in the temporal domain of the LL band;

(f) applying an inverse wavelet transform in the spatial domains of the LL, LH, HL, and HH bands; and

(g) outputting decompressed video data resulting from step (f).

14. The method of claim 13 wherein the steps of applying an inverse wavelet transform in the temporal domain of the LL band and the spatial domain of the LL, LH, HL, and HH bands comprises the steps of applying an inverse integer-based wavelet transform.

15. The method of claim 13 wherein the step of dequantizing wavelet coefficients in step (b) comprises the step of dequantizing wavelet coefficients in accordance with the adaptive dead zone method.

16. The method of claim 13 wherein the steps of decoding quantized wavelet coefficients from steps (a) and (c) comprises the step of stack run decoding the wavelet coefficients.

17. A method for real-time compression of video data comprising the steps of:

(a) applying 2D wavelet transform to each video frame to decompose an image into LL, LH, HL, and HH subbands;

(b) within the LL subbands,

(i) comparing a current video frame to a next video frame to compute a difference between the frames;

(ii) assigning the current video frame to a current group if the difference is less than or equal to a threshold;

(iii) assigning the current video frame to a new group if the difference is greater than the threshold;

(c) for each group created in accordance with step (b), applying 3D wavelet transform to all the frames in the group;

(d) quantizing the wavelet coefficients resulting from step (c);

(e) encoding the quantized wavelet coefficients resulting from step (d); and

(f) outputting the encoded quantized wavelet coefficients from steps (e).

18. The method of claim 17 wherein the step of applying 2D wavelet transform to each video frame to generate LL, LH, HL, and HH subbands comprises the step of applying integer-based wavelet transform to each video frame.

19. The method of claim 18 wherein the step of applying integer-based wavelet transform comprises the step of applying a packed computation method to the integer-based wavelet transform.

20. The method of claim 17 wherein the step of quantizing wavelet coefficients in step (d) comprises the step of quantizing wavelet coefficients in accordance with the adaptive dead zone method.

21. The method of claim 17 wherein the step of encoding the quantized wavelet coefficients comprises the step of stack run encoding the quantized wavelet coefficients.

22. The method of claim 17 further comprising the steps of:

(g) decoding the encoded quantized wavelet coefficients of the plurality of frame groups of the LL, LH, HL, and HH subbands;

(h) dequantizing wavelet coefficients in the plurality of frame groups of the LL, LH, HL, and HH subbands;

(i) applying an inverse wavelet transform in the temporal domain of the LL, LH, HL, and HH subbands; and

(j) outputting decompressed video data resulting from step (i).