Image Coding for Underwater Transmission

We describes here a JPEG based compression scheme, adjusted specific for the underwater acoustical channel. The project goal was to deal with common bit error rates for the underwater acoustic channel, . Tow measures were used to quantify different solutions: compression ratio, which we tried to minimize, and SSIM, a measure that describes the quality of the image, which we tried to maximize.
The scheme described in this report was inspired by initial research conducted by RAFAEL, common schemes to deal with errors in images, and intensive acquaintance with the international JPEG compression standard. The implemented scheme was tested on a variety of images and the results are described in detail in this report.

Introduction (The problem or the background)

In the past recent years, the usage of underwater applications was widely increased in both military and civilian industries. In order for those application to share information, a reliable communication scheme is to be archived using the underwater acoustic channel.
In this project we discussed image transmission through the underwater acoustic channel which is characterized by high bit error probability and slow communication rate. A naïve solution is to use the JPEG compression standard, however JPEG has zero tolerance for errors and a better solution should be found.

JPEG compressed image as decoded after being transmitted through the underwater acoustic channel.

The solution (or the basic approach)

In this project we created a JPEG based compression scheme that is adjusted for the underwater acoustic channel. We chose JPEG as the initial scheme due to the importance of compression ratio and its simplicity. Several features were added in order to deal with errors which make it a robust compression scheme.

Figure 1 - Block diagram of the solution. Several features were added to the original JPEG standard.

Initial results, conducted by RAFAEL:

Our compression scheme results:

In order to deal with the mentioned problem several features were added to the original JPEG standard. We analyzed the scheme’s performance using SSIM, and the image compression ratio on a large variety of images.
Finally, we created a robust JPEG based compression scheme adjustable for the underwater acoustic channel. The scheme adds up to 25 percent overhead for the compressed image size (comparing with the original JPEG standard) and can be modified according to the user’s preferences.
[1] G. Wallace, The JPEG Still Picture Compression Standard1991 .
[2] A. Puri, X. Chen ו A. Luthra, Video Coding Using the H.264/MPEG-4 AVC Compression Standart, Signal Proccesing: Image Communication. 2004
[3] S. Kumar, L. Xu, M. Mandal ו S. Panchanathan, Error Resilency Schemesin H.264 standard, Visual communication&Image Representation. 2006

underwater image


Robust Underwater Image Compression
Robust Underwater Image Compression

Dr. Alon Amar,


Project web page