JPG in MMS

How MMS mobile phones handles corrupted Multimedia Messages?

Student: Zoran Sambol Professor: Nikola RožićMultimedia Communications, FESB, University of Split

Task definition

• Multimedia communications is postgraduate study subject. FESB, University of Split

• Task was to exam how mobile phones handle corrupted JPEG images which are part of MM (Multimedia Message).

• Objective for task is student business participation in MMS project.

JPEG standard

• JPEG is generic standard for continuous-tone still images – grayscale and color.

• DCT-based method for “lossy” compression and predictive method for “loseless” compression.

• Four steps algorithm:– Initialization - MCU– DCT– Quantization– Encoding (Huffman or arithmetic coding)

• File formats – JFIF and SPIFF• M-JPEG is non-standard JPG variant

JPEG algorithm

• The JPEG Still Picture Compression Standard• JPEG Overview• JPEG File Interchange Format• JPEG File Layout and Format

Independent JPG Group

• A consortium of programmers, the Independent JPEG Group (IJG), has produced a public domain version of a JPEG encoder and decoder in C source code form.

• IJG library can be obtained from various FTP sites, information services, and computer bulletin boards.

• Basic JPG Reference to IJG library - FAQ

• Many projects use IJG – Internet search results

• IJG ReadMe file

• Source code - ftp download or link to disk

IJG JPEG usage

• C software for JPEG image compression and decompression

• Set of library routines plus sample applications cjpeg and djpeg – Usage

• The library is intended to be reused in other applications – APIs

• Project documentation: install, library and application usage, wizards, examples, structure, file list and code rules

Restart markers

IJPG Group console applications cjpeg (compress) and jpegtran (transformations) use “-restart” option.- restart N - Emit a JPEG restart marker every N MCU rows, or every N MCU blocks if "B" is attached to the number. -restart 0 (the default) means no restart markers.

The -restart option inserts extra markers that allow a JPEG decoder to resynchronise after a ttransmission error. Without restart markers, any damage to a compressed file will usually ruin the image from the point of the error to the end of the image; with restart markers, the damage is usually confined to the portion of the image up to the next restart marker. Of course, the restart markers occupy extra space. We recommend -restart 1 for images that will be transmitted across unreliable networks such as Usenet.

CImage freeware

• Freeware windows imaging application (JPG, BMP, GIF, PNG, TIF and ICO)

• IJPG library reused as a DLL

• Visual studio MFC MDI project

Mobile manufacturer implementation

• Mobile manufacturer uses IJG library in unchanged form – copyright notice exists– Copyright (C) 1994-1996, Thomas G. Lane.

• Wrapper functions in MMS client

• Basic IJG functionality remains

Mobile phones test

• Mobile phone with camera used• JPG image captured• Image uploaded to PC and its content was

randomly corrupted• Corrupted image downloaded to Mobile• MMS with corrupted image created and sent to

mobile• Received MMS show same image as a PC

Test images

Mobile phone camera image Corrupted image

Conclusion

• Mobiles’ MMS clients uses same JPG engine as PC

• In different mobile phones MMS corrupted images are handled on the same way

• Manufacturers uses IJPG library which is reasonable due to software development cost reduction