Cadence analysis for a video signal having an interlaced format

1. A method of processing a video signal in a video processing unit, the video signal having an interlaced format and comprising a sequence of fields, the method comprising:

obtaining motion indicators for blocks of a plurality of fields of the video signal;

using said obtained motion indicators to determine cadence signatures for blocks of a field of said plurality of fields, wherein the cadence signatures are indicative of one or more cadences of the video signal;

creating a histogram of determined cadence signatures of said blocks of said field; and

determining the position of one or more peaks in the histogram to thereby determine one or more significant cadence signatures in said field;

whereby the fields of the video signal are processed in accordance with one or more determined significant cadence signatures to thereby determine frames of the video signal.

2. The method of claim 1 wherein the motion indicators are motion vectors.

3. The method of claim 1 wherein the motion indicators are binary flags, wherein the binary flag for a block in a particular field has a first binary value if there is substantially no motion in the block of the particular field, and wherein the binary flag for the block in the particular field has a second binary value if there is substantially some motion in the block of the particular field.

4. The method of claim 2 wherein said using the obtained motion vectors to determine cadence signatures comprises, for each of the blocks of the plurality of fields:

assigning a binary flag to the block based on the obtained motion vector for the block.

5. The method of claim 1 wherein said obtaining the motion indicators comprises either: (i) determining the motion indicators in a motion analysis module of the video processing unit, or (ii) receiving the motion indicators which have been determined by a motion analysis module which is separate to the video processing unit.

6. A video processing unit configured to process a video signal, the video signal having an interlaced format and comprising a sequence of fields, the video processing unit being configured to obtain motion indicators for blocks of a plurality of fields of the video signal, wherein the video processing unit comprises:

a cadence analysis module configured to:

use said obtained motion indicators to determine cadence signatures for blocks of a field of said plurality of fields, wherein the cadence signatures are indicative of one or more cadences of the video signal;

create a histogram of determined cadence signatures of said blocks of said field; and

determine the position of one or more peaks in the histogram to thereby determine one or more significant cadence signatures in said field;

wherein the video processing unit is configured to process the fields of the video signal in accordance with one or more determined significant cadence signatures to thereby determine frames of the video signal.

7. The video processing unit of claim 6 wherein the video signal includes video content of one or more type from a set of available video content types which have different cadences, said set of available video content types including an interlaced content type and a progressive content type, and wherein the cadence analysis module is further configured to:

use the determined cadence signatures to determine the one or more types of the video content in the video signal.

8. The video processing unit of claim 7 wherein the cadence analysis module is configured to:

determine a cadence signature for each of the blocks in said field; and

assign each of the blocks in said field to one of the video content types based on the determined cadence signature for that block.

9. The video processing unit of claim 8 wherein the cadence analysis module is further configured to:

determine the number of blocks in said field which are assigned to the progressive content type;

wherein said histogram is a histogram of the determined cadence signatures of the blocks in said field which are assigned to the progressive content type, and wherein the cadence analysis module is configured to create said histogram responsive to determining that the number of blocks in said field assigned to the progressive content type exceeds a threshold.

10. The video processing unit of claim 6 wherein the cadence analysis module is further configured to map the determined one or more significant cadence signatures to one or more cadences of the video signal.

11. The video processing unit of claim 10 wherein the one or more cadences are one or more known cadences from a set of known cadences which have known cadence signatures, and wherein the cadence analysis module is configured to map each of the one or more significant cadence signatures to a known cadence by determining which of the known cadence signatures of the known cadences has the greatest similarity with the significant cadence signature.

12. The video processing unit of claim 11 wherein the cadence analysis module is configured to determine which of the known cadence signatures of the known cadences has the greatest similarity with the significant cadence signature by determining which of the known cadence signatures of the known cadences has a smallest distance to the significant cadence signature.

13. The video processing unit of claim 12 wherein the smallest distance is a smallest Hamming distance.

14. The video processing unit of claim 11 wherein the cadence analysis module is further configured to, for each block of a particular field:

determine a respective measure of the similarity between the cadence signature of the block and each of: (i) the known cadence signatures of the known cadences, (ii) a cadence signature indicative of interlaced content, and (iii) a cadence signature indicative of static content; and

assign, to the block, the cadence or content type which has the greatest similarity according to the determined measures of similarity.

15. The video processing unit of claim 6 , wherein the motion indicators are binary flags, wherein the binary flag for a block in a particular field has a first binary value if there is substantially no motion in the block of the particular field, and wherein the binary flag for the block in the particular field has a second binary value if there is substantially some motion in the block of the particular field, and wherein the cadence analysis module is configured to use the obtained motion vectors to determine cadence signatures by, for each of the blocks:

concatenating the binary flags for the block over a sequence of consecutive fields of the video signal to thereby determine a cadence signature for the block.

16. The video processing unit of claim 6 wherein the cadence analysis module is further configured to use the determined cadence signatures to derive field pairings of consecutive fields which relate to the same time instance of the video content.

17. The video processing unit of claim 16 wherein the motion indicators are binary flags, wherein the binary flag for a block in a particular field has a first binary value if there is substantially no motion in the block of the particular field, and wherein the binary flag for the block in the particular field has a second binary value if there is substantially some motion in the block of the particular field, and wherein the cadence analysis module is configured to derive the field pairings by finding the first binary value in the most recent elements of the cadence signatures for the blocks of a field.

18. A method of processing a video signal in a video processing unit, the video signal having an interlaced format and comprising a sequence of fields, the method comprising:

obtaining motion indicators for blocks of a plurality of fields of the video signal;

using the obtained motion indicators to determine cadence signatures which are indicative of one or more cadences of the video signal; and

using the determined cadence signatures to identify one or more cadences of the video signal by: (i) identifying one or more prevalent cadence signatures from the determined cadence signatures, and (ii) mapping each of the one or more prevalent cadence signatures to a known cadence from a set of known cadences which have known cadence signatures by determining which of the known cadence signatures of the known cadences has a smallest distance to the prevalent cadence signature;

wherein the fields of the video signal are to be processed in accordance with the identified one or more cadences to thereby determine frames of the video signal.

19. The method of claim 18 wherein said smallest distance is a smallest Hamming distance.

20. The method of claim 18 wherein the video signal includes video content of one or more type from a set of available video content types which have different cadences, said set of available video content types including an interlaced content type and a progressive content type, and wherein the method further comprises:

using the determined cadence signatures to determine the one or more types of the video content in the video signal,

wherein said determining cadence signatures comprises determining a cadence signature for each of the blocks, and wherein the method further comprises:

assigning each of the blocks to one of the video content types based on the determined cadence signature for that block;

determining the number of blocks which are assigned to the progressive content type;

if the number of blocks assigned to the progressive content type exceeds a threshold, creating a histogram of the cadence signatures of the blocks assigned to the progressive content type; and

determining the position of one or more peaks in the histogram to thereby identify said one or more prevalent cadence signatures in the video signal.

21. A video processing unit configured to process a video signal, the video signal having an interlaced format and comprising a sequence of fields, the video processing unit being configured to obtain motion indicators for blocks of a plurality of fields of the video signal, wherein the video processing unit comprises:

a cadence analysis module configured to use the obtained motion indicators to determine cadence signatures which are indicative of one or more cadences of the video signal, and to use the determined cadence signatures to identify one or more cadences of the video signal by: (i) identifying one or more prevalent cadence signatures from the determined cadence signatures, and (ii) mapping each of the one or more prevalent cadence signatures to a known cadence from a set of known cadences which have known cadence signatures by determining which of the known cadence signatures of the known cadences has a smallest distance to the prevalent cadence signature,

wherein the video processing unit is configured to process the fields of the video signal in accordance with the identified one or more cadences to thereby determine frames of the video signal.

22. A non-transitory computer readable storage medium having stored thereon processor executable instructions that when executed cause at least one processor to process a video signal in a video processing unit, the video signal having an interlaced format and comprising a sequence of fields, the processing of the video signal comprising:

obtaining motion indicators for blocks of a plurality of fields of the video signal;

using said obtained motion indicators to determine cadence signatures for blocks of a field of said plurality of fields, wherein the cadence signatures are indicative of one or more cadences of the video signal;

creating a histogram of determined cadence signatures of blocks of said field; and

determining the position of one or more peaks in the histogram to thereby determine one or more significant cadence signatures in said field;

wherein the fields of the video signal are to be processed in accordance with one or more determined significant cadence signatures to thereby determine frames of the video signal.

23. A non-transitory computer readable storage medium having stored thereon processor executable instructions that when executed at a computer system for generating a representation of a digital circuit from definitions of circuit elements and data defining rules for combining those circuit elements, cause the computer system to generate a video processing unit configured to process a video signal, the video signal having an interlaced format and comprising a sequence of fields, the video processing unit being configured to obtain motion indicators for blocks of a plurality of fields of the video signal, wherein the video processing unit comprises:

a cadence analysis module configured to:

use said obtained motion indicators to determine cadence signatures for blocks of a field of said plurality of fields, wherein the cadence signatures are indicative of one or more cadences of the video signal;

create a histogram of determined cadence signatures of the blocks of said field; and

determine the position of one or more peaks in the histogram to thereby determine one or more significant cadence signatures in said field;

wherein the video processing unit is configured to process the fields of the video signal in accordance with one or more determined significant cadence signatures to thereby determine frames of the video signal.