Variable resolution decoder
View Patent ↗A variable resolution decoder of the present invention decodes image data compressed with a compression method such as MPEG-2 supporting interlaced scanning. The decoder performs variable decoding and inverse quantization on the compressed image data and then checks a DCT mode of a frame, performs inverse discrete cosine transform in 4 by 8 pixels when the mode is a DCT mode, acquires image data of full resolution for interlaced scanning in a vertical direction, and thins the image data, thereby performing image reduction of the image data during decoding with field information maintained. The decoder comprises means for performing reduction in a DCT area for resolution of image data in a horizontal direction and means for performing reduction in a pixel area for resolution of image data in a vertical direction.
1. A variable resolution decoder for decoding image data compressed with a compression method such as MPEG-2, said decoder comprising:
means for performing variable length decoding and inverse quantization on the compressed image data;
means for checking a discrete cosine transform mode of a frame and performing inverse discrete cosine transform in 4 by 8 pixels when the mode is a discrete cosine transform mode; and
means for acquiring image data of full resolution for interlaced scanning in a vertical direction and thinning interlaced scanned image data to perform image reduction processing during decoding with field information maintained.
2. A variable resolution decoder for decoding image data compressed with a compression method such as MPEG-2, said decoder comprising:
means for performing variable length decoding and inverse quantization on the compressed image data;
means for checking a discrete cosine transform mode of a frame and performing reduction processing in a discrete cosine transform area for resolution of interlaced scanning in a horizontal direction; and
means for performing reduction processing in a pixel area for resolution of interlaced scanning in a vertical direction wherein,
the reduction in vertical resolution is performed using even or odd lines in a top field and the other line in a bottom field.
3. The variable resolution decoder according to claim 2 , wherein said means for performing reduction processing in said discrete cosine transform area is field inverse discrete cosine transform processing means for performing inverse discrete cosine transform processing in a field discrete cosine transform mode.
4. The variable resolution decoder according to claim 2 , wherein said means for performing reduction processing in said pixel area is frame inverse discrete cosine transform processing means for performing inverse discrete cosine transform processing in a frame discrete cosine transform mode.
5. A variable resolution decoder for decoding image data compressed with a compression method such as MPEG-2, said decoder comprising:
means for performing variable length decoding and inverse quantization on the compressed image data;
means for selecting a discrete cosine transform mode;
means for checking a discrete cosine transform mode of a frame and performing inverse discrete cosine transform in 4 by 8 pixels when the mode is a frame discrete cosine transform mode; and
means for acquiring image data of full resolution for interlaced scanning in a vertical direction and thinning interlaced scanned image data,
wherein the image data is decoded such that the image has lowered resolution at the time of display.
6. A variable resolution decoder for decoding image data compressed with a compression method such as MPEG-2, said decoder comprising:
means for performing variable length decoding and inverse quantization on the compressed image data;
means for checking a discrete cosine transform mode of a frame and performing inverse discrete cosine transform in 4 by 8 pixels when the mode is a discrete cosine transform mode; and
means for acquiring image data of full resolution for interlaced scanning in a vertical direction and thinning interlaced scanned image data,
wherein the image data is decoded such that the image has lowered resolution at the time of display.
7. The variable resolution decoder according to claim 5 , wherein said means for thinning image data takes only even-numbered lines of said interlaced scanned image data and calculates the averages of two adjacent taken lines which are used as data of top field, and takes only odd-numbers lines of said interlaced scanned image data and calculates the averages of two adjacent taken lines which are used as data of bottom field to decode the image data at halved resolution both vertically and horizontally with field information maintained.
8. The variable resolution decoder according to claim 6 , wherein said means for thinning image data takes only even-numbered lines of said interlaced scanned image data and calculates the averages of two adjacent taken lines which are used as data of top field, and takes only odd-numbers lines of said interlaced scanned image data and calculates the averages of two adjacent taken lines which are used as data of bottom field to decode the image data at halved resolution both vertically and horizontally with field information maintained.