The input JPEG and output Features:
Table 1 : jpegDecoder Features
| jpegDecoder | Status |
|---|---|
| Input | support JPEG that scaned by baseline sequential processing 8-bit precision |
| Output | YUV with the mcu scan order |
| Output info | Image width, height, scan format, quantization tables, number of mcu, other details… the reason for the decoding error if there is |
| performance | decode one Huffman symbol in 1 cycle Output YUV raw data 8 Byte per cycle with the mcu scan order |
The algorithm implemention is shown as the figure below:
Figure 2 : jpegDecoder architecture on FPGA
As we can see from the figure:
The design uses the special statistical characteristics of jpeg compression, that is, in most cases, the (huffman length + value length) is less than 15, and each clock cycle can solve a huffman symbol.