Rapid production of reduced-size images from compressed video streams

• US 7,471,834 B2
• Filed: 02/10/2003
• Issued: 12/30/2008
• Est. Priority Date: 07/24/2000
• Status: Active Grant

• Current Assignee: Scenera, Inc.
• Original Assignee: VMark, Inc. (VALID Soluciones Tecnológicas SA)
• Inventors: Sull, Sanghoon, Chun, Seong Soo, Suh, Sungjoo, Kim, Jung Rim
• Primary Examiner(s): Alavi; Amir
• Application Number:
  US10/361,794
• Publication Number:
  US 20040126021A1
• Time in Patent Office: 2,150 Days
• Field of Search: 382/232, 382/233, 382/235, 382/236, 382/240, 382/248, 382/250, 382/251, 382/253, 386/68, 375/240.03, 375/240.11, 375/240.16, 375/240.2, 375/240.22, 375/240.24, 375/240.25
• US Class Current: 382/232
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11B 2220/41 Flat as opposed to hierarchical combination, e.g. library of tapes or discs, CD changer, or groups of record carriers that together store one title
• CPC Class Codes: G11B 27/034 on discs G11B27/036, G11B27/038 take precedence
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: G11B 27/28 by using information signals recorded by the same method as the main recording G11B27/22 takes precedence
• CPC Class Codes: G11B 27/34 Indicating arrangements indicating means incorporated in magazine or cassette G11B23/046 and G11B23/0875; indicating measured values in general G01D

Abstract

Methods for fast generating spatially reduced-size images directly from compressed video streams supporting the coding of interlaced frames through transform coding and motion compensation. A sequence of reduced-size images are rapidly generated from compressed video streams by efficiently combining the steps of inverse transform, down-sampling and construction of each field image. The construction of reduced-size field images also allows the efficient motion compensation. The fast generation of reduced-size images is applicable to a variety of low-cost applications such as video browsing, video summary, fast thumbnail playback and video indexing.

Claims

1. A method for producing reduced-size images from a video stream, comprising:

selecting a reduced set of transform coefficients from each of a plurality of macroblocks by discarding higher-frequency coefficients in response to a reduction factor; and

performing an inverse transformation and field separation process on the selected coefficients to produce reduced-size top-field and bottom-field image blocks.

2. A method according to claim 1, wherein:

the reduced set of transform coefficients comprises at least one transform coefficient from each of the plurality of macroblocks.

3. A method according to claim 1, further comprising:

retrieving the reduced set of transform coefficients by performing the additional steps of;

decoding the macroblocks to produce the reduced set of transform coefficients in a quantized form; and

dequantizing the reduced set of transform coefficients.

4. A method according to claim 1, wherein:

the reduction factor is expressed as a ratio M/N, where;

M and N are both positive, nonzero integers; and

M is less than N.

5. A method according to claim 4, wherein:

each macroblock further comprises a plurality of transform blocks, each transform block comprising an N×

N array of transform coefficients.

6. A method according to claim 5, wherein:

the transform coefficients are Discrete Cosine Transform (DCT) coefficients.

7. A method according to claim 5, wherein:

the macroblocks are field DCT encoded; and

the selected set of transform coefficients comprises 2M×

M arrays of transform coefficients from each of a plurality of transform blocks.

8. A method according to claim 5, wherein:

the macroblocks are frame DCT encoded; and

the selected set of transform coefficients comprise M×

M arrays of transform coefficients from each of a plurality of transform blocks.

9. A method according to claim 1, wherein:

the reduced-size image comprises a frame image.

10. A method according to claim 1, wherein:

the reduced-size image comprises a field image.

11. The method of claim 1, wherein each macroblock comprises at least two blocks.

12. A method according to claim 1, wherein the macroblocks lie along a sampling path of a video frame, and the reduced size image is a line image, and further comprising:

producing a visual rhythm image of the video stream by stacking a plurality of line images alongside one another.

13. The method of claim 1, utilized for at least one of video browsing, video summary, fast thumbnail playback and video indexing.

14. A device being arranged for executing a method as claimed in claim 1.

15. A thumbnail generator comprising:

means for determining a reduction factor for a reduced size image;

means, responsive to said reduction factor, for selecting a reduced set of transform coefficients from each of a plurality of macroblocks by discarding higher-frequency coefficients; and

means for performing an inverse transformation and field separation process on the selected coefficients to produce reduced-size top-field and bottom-field image blocks.

16. A system according to claim 15, further comprising:

means for adjusting the reduced-size image pixel values according to motion vector information within the video stream.

17. A system according to claim 15, wherein:

the video stream is an MPEG-2 video stream.

18. A computer readable medium carrying a set of instructions which, when performed, execute a method comprising:

selecting a reduced set of transform coefficients from each of a plurality of macroblocks by discarding higher-frequency coefficient in response to a reduction factor; and

performing an inverse transformation and field separation process on the selected coefficients to produce reduced-size top-field and bottom-field image blocks.