ml87v3116 Oki Semiconductor, ml87v3116 Datasheet - Page 20

• Manufacturer Part Number: ml87v3116
• Description: Display Controller With Built-in Display Memory And Jpeg
• Manufacturer: Oki Semiconductor

2.3 JPEG Codec
2.3.1 General Description
2.3.2 Still Picture Mode and Moving Picture Mode
OKI Semiconductor
JPEG Codec compresses and decompresses image data.
When compressing images, JPEG Codec uses a rectangle area specified in the Data Buffer as the source image,
sequentially reads data into block forms, compresses data using the JPEG method, and then converts the
compressed data to a compressed data file in the JFIF format. This compressed data file is written in the
rectangle area from the start address specified in the Data Buffer. Compression formats such as block
interleave are in accordance with the JPEG baseline standard. Set the source image size, quantization table and
Huffman table using control registers in advance. Color components only support the 2:1:1 format equivalent
to 4:2:2 of video. For image compression, the sequential compression of input image data can be performed by
conducting an operation simultaneously with image input.
When decompressing images, JPEG Codec sequentially reads a compressed data file from the start address
specified in the Data Buffer, decompresses data using the JPEG method, placing restored data block again, and
reconstructing images. Decompressed images are sequentially written from the start address specified in the
Data Buffer in block units. The image size, quantization table and Huffman table are extracted from a
compressed data file in the JFIF format.
Compression and decompression operations are available in two modes: still picture mode and moving picture
mode.
In the still picture mode, an operation starts by writing to the startup register, and ends when the processing of
one image “frame” completes. Also, an operation can temporarily be stopped for each number of specified
lines. This makes it possible to process images having the number of pixels larger than the memory buffer
capacity. It does not relate to the restart marker RSTm.
The moving picture mode is a repetition of operations in the still picture mode. By automatically managing the
addresses of compressed data files, multiple files can sequentially be compressed or decompressed. An
operation in the moving picture mode is started by writing to the startup register, and ended after the
completion of a series of specified operations, or the same operation is repeated.
When recording (compressing) moving pictures, the operation is synchronized with the frame timing of video
input. When playing back (decompressing) moving pictures, the operation is synchronized with the frame
timing of video output.
During an moving picture recording operation, the same image size, quantization table and Huffman table are
used for all frames. They cannot be changed during recording.
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