Parallel decode of a progressive JPEG bitstream
View Patent ↗A progressive JPEG bitstream may comprise an image component that is comprised of multiple scans of MCUs/data units that are in turn comprised of at least one MCU/data unit segment. Each MCU/data unit segment is successively scanned. The MCU/data unit segment is then reconstructed using multiple entropy decoders operating in parallel on different scans of each MCU/data unit segment.
1. A method of processing a progressive image bitstream, the method comprising:
determining whether a data unit segment of an image is in a user-specified region of interest;
successively scanning the data unit segment of the image in the progressive image bitstream to produce two or more scans;
decoding, in parallel, the two or more scans of the data unit segments; and
reconstructing the data unit segment according to the two or more decoded scans of the data unit segment, wherein the data unit segment is reconstructed with a higher image quality if the data unit segment is in the user-specified region of interest.
2. The method of claim 1 , wherein decoding comprises utilizing multiple entropy decoders.
3. The method of claim 1 , wherein the data unit segment is between two synchronization points.
4. The method of claim 1 , wherein decoding comprises temporarily storing a discrete cosine transform (DCT) coefficient of the data unit segment in an output image buffer.
5. The method of claim 1 , wherein the data unit segment comprises ¼ th of frequency coefficients that are present in a top-left 4×4 array of an 8×8 a data unit block.
6. The method of claim 1 , wherein the data unit segment comprises an approximation of at least one image component using stored DCT coefficients.
7. The method of claim 1 , wherein the method comprises up-scaling reconstructed sub-sampled approximations of the data unit segment.
8. A system for processing a progressive image bitstream comprising:
a user interface operable to identify whether a data unit segment of an image is in a region of interest;
a scanner operable to successively scan a data unit segments of an image in the progressive image bitstream to produce two or more scans;
two or more decoders operable in parallel to decode the two or more scans of the data unit segment; and
a circuit operable to reconstruct the data unit segment according to the two or more decoded scans of the data unit segment, wherein the data unit segment is reconstructed with a higher image quality if the data unit segment is in the region of interest.
9. The system of claim 8 , wherein the two or more decoders are two or more entropy decoders.
10. The system of claim 8 , wherein the data unit segment is between two synchronization points.
11. The system of claim 8 , wherein the system comprises an output image buffer operable to temporarily store a discrete cosine transform (DCT) of the data unit segment.
12. The system of claim 8 , wherein the data unit segment comprises ¼ th of frequency coefficients that are present in a top-left 4×4 array of an 8×8 a data unit block.
13. The system of claim 8 , wherein the data unit segment comprises an approximation of at least one image component using stored DCT coefficients.
14. The system of claim 8 , wherein the circuit is operable to up-scale reconstructed sub-sampled approximations of the data unit segment.
15. The non-transitory computer-executable storage medium of claim 8 , wherein the parallel decoding comprises entropy decoding.
16. A non-transitory computer-executable storage medium comprising program instructions which are computer-executable to implement:
program instructions that receive an input from a user interface to identify whether a data unit segment of an image is in a region of interest;
program instructions that cause a production of two or more scans of a data unit segment, the data unit segment being an element of an image in a progressive image bitstream;
program instructions that cause a parallel decoding of the two or more scans of the data unit segment; and
program instructions that cause a reconstruction of the data unit segment according to the two or more decoded scans of the data unit segment, wherein the data unit segment is reconstructed with a higher image quality if the data unit segment is in the region of interest.
17. The non-transitory computer-executable storage medium of claim 16 , wherein the data unit segment is between two synchronization points.
18. The non-transitory computer-executable storage medium of claim 16 , wherein the program instructions cause a discrete cosine transform (DCT) of the data unit segment to be temporarily stored in an output image buffer.
19. The non-transitory computer-executable storage medium of claim 16 , wherein the data unit segment comprises ¼ th of frequency coefficients that are present in a top-left 4×4 array of an 8×8 a data unit block.
20. The non-transitory computer-executable storage medium of claim 16 , wherein the data unit segment comprises an approximation of at least one image component using stored DCT coefficients.
21. The non-transitory computer-executable storage medium of claim 16 , wherein the program instructions cause a reconstructed sub-sampled approximations of the data unit segment to be up-scaled.