JPEG Still Image Compression
for TMS320C3x/'C4x
by DSP Software Engineering, Inc.

Software Overview

The JPEG software is an implementation of the Joint Photographic Experts Group (JPEG) standards for 
still-image compression for the TMS320C3x. JPEG is composed of several variable-rate compression 
techniques for still images. This implementation performs the following operations:
•	Pixel Blocking
•	Zig-Zag Scanning
•	Discrete Cosine Transform
•	Run-Length Coding
•	Quantization
•	Huffman Coding

Features and Benefits

•	Fully compliant with the JPEG-8-R8 baseline specification
•	Object oriented, C-callable functions
•	Supports 8-, 16-, or 24-bit images, both greyscale and full color
•	SPOX compatible
•	Variable compression ratios and user-definable frame size

Processor and System Requirements

•	Devices supported: TMS320C3x, TMS320C4x
•	Algorithm category: Image
•	Requirements:
All memory requirements are in units of 32-bit words. The MIPs ratings presented require the listed 
amounts of on-chip, zero-wait-state program and data memory, operating on a 256 ¥ 240 pixel image.  
All measurements were made using an executable demonstration built for a third-party PC plug-in 
board.
Function
(Compression Resolution)
MIPS
Chip RAM
Data
Program
Grey Scale Encode (High/Low)
5.6 / 4.5
2 k
0.5 k
2.5 k
Grey Scale Decode (High/Low)
7.8 / 6.6
2 k
0.5 k
6.8 k
RGB Encode (High/Low)
11.0 / 9.0
2 k
0.5 k
2.5 k
RGB Decode (High/Low)
15.2 / 12.5
2 k
0.5 k
6.8 k
Full-Duplex 8-bit Grey Scale*
13.4 / 11.1
2 k
0.5 k
9.3 k
Full-Duplex 24-bit RGB*
26.2 / 21.5
2 k
0.5 k
9.3 k
* Significant portions of read-only data are shared by the encoder and decoder.

User Functions

This JPEG implementation consists of four independent, C-callable functions that perform encoding 
and decoding operations. It also includes functions that reflect the implementation's object-based 
interface. The encoder and decoder interface with linear arrays of 8-, 16-, or 24-bit pixels and 
8-bit code words.
JPEG Encoder
JPEG_encoder_int (...)
Encodes a block of pixels from an interlaced image into code words
JPEG_encoder_nint (...)
Encodes a block of pixels from a non-interlaced image into code words
JPEG Decoder
JPEG_decoder_int (...)
Decodes a block of code words into pixels in an interlaced image
JPEG_decoder_nint (...)
Decodes a block of code words into pixels in a non-interlaced image
Common
JPEG_xxx_bufint (...)
Initializes JPEG encoder or decoder for interlaced operation
JPEG_xxx_bufnint (...)
Initializes JPEG encoder or decoder for non-interlaced operation

Company Background and Contact Information

DSP Software Engineering, Inc. (DSPSE), founded in 1989, is a leading provider of highly-complex 
digital-signal-processing software used in telecommunications and multimedia applications such as 
computer telephony, digital wireless, PSTN, and satellite communications, and videoconferencing.
Contact:	DSP Software Engineering, Inc.
		175 Middlesex Turnpike
		Bedford, MA 01730  USA
		(617) 275-3733
		Fax: (617) 275-4323
		e-mail:  info@dspse.com
		www:  http://www.dspnet.com