Samsung S5PC110 Manual page 1750

S5PC110_UM
12.6.4 PROCESS FOR IMAGE SIZE
Size of images in JPEG file has to be a specific value, which is the multiple of block size because JPEG file is
composed of blocks. If image size in JPEG file header is not multiple of block size, actual image size in the file is
the minimum among values which are the multiple of the block size and larger than the value in the header, but
decoder shows cropped image with the size in file header. Minimum size for compression and decompression
process is double of Block Size. Color format determines the block size as described in
Color format
YCbCr4:4:4
YCbCr4:2:2
YCbCr4:2:0
Gray (Y only)
1. Decompression
Input JPEG file has information about color format, width and height of the image in the frame header. User
knows the information about the JPEG file after header parsing process. Actual raw image size after
decompression is the minimum among the values which are the multiple of block size (known from color
format) and larger than or equal to the image size in the header. For example, if JPEG file is YCbCr4:2:0
format and its size is 170x170, actual size of decompressed raw image is 176x176.
2. Proper process such as cropping is needed to display or store the result raw image in the width and height of
the file header.
3. Compression
Width and height of input raw image must be the multiple of the block size corresponding to the output JPEG
color format. If input raw image has arbitrary size, use padding process to modify the size to the multiple of
block size. The modified size is the minimum values which are the multiple of the block size and larger than or
equal to the original value. However, register setting value of width and height for compression must be the
original value.
12.6.5 PROCESS FOR INPUT STREAM SIZE
For decompression of an illegal JPEG stream, JPEG core does not recognize the end of the stream if some
important markers are damaged. Therefore, it is necessary to notify the input stream size to JPEG core.
Table 12-2 Relationship between Block Size and Color Format
MCU Block size (WxH)
8x8
16x8
16x16
8x8
12 11BJPEG
Table 12-2.
Minimum size
16x8 or 8x16
32x8 or 16x16
32x16 or 16x32
16x8 or 8x16
12-8