“Investigating the SWF file format” -or- “What I did in my summer holidays” Deconstructing Flash

Introduction Simon Wistow –Computing BEng Ian Harries –Supervisor Iain Phillips –Second Marker

Flash? A little bit of History –FutureSplash was originally created by FutureWave –FutureWave bought by MacroMedia, FutureSplash renamed “Flash” –Current version is 4. –Flash file format (SWF) was open-sourced in 1998

Flash? Vector animation format –Shapes and Lines –Bitmaps (JPEGs, PNGs) –Sounds (ADPCMs, MP3s) These are known as objects –analogous to actors, scenery and soundtrack

Flash Keeping with the film analogy –SWF format is a script to describe and control the ‘actors’. –Divided into frames –frames divided into tags these define and control objects –34 different tags, using 17 data-types

Flash? Web Oriented –Highly compressed –Plug-in –Pseudo-Streaming

Flash? Scriptable –Control Events, within movie –Reactive not truly dynamic

The idea I needed –A tool for manipulating Flash files –A way of creating Flash files from scratch –Some way of converting between formats Abstract Representation

Why? Can’t create totally dynamic content –prevents uses on database applications Because it’s complicated –it can’t be used within other applications, the facilities don’t exist –You can't do some things with the existing interface Storing SWF binary is not always appropriate

The Competition Macromedia Generator –Limited Modification not creation –Expensive(very) And you still need Flash Authoring tool –Slow –Resource Intensive

The Competition Ming –Enemy of flash –PHP based –Unfinished, only generates

The Competition XML-FLASH –Java Based –Limited to conversion into and out of XML –Unfinished

The Competition Middlesoft SDK –Finished near project end –Limited to C++ on Windows –Complicated –Restrictive Licensing –Creation Only

How File::Binary –Perl module for binary manipulation of files de-compilation/ reverse engineering –Finding errors in the released specification

How creation of abstract Flash library –Object Structure creation of SWF generation library –XS wrapping of libswf

Achievements SWF Parser Flash Object SWF Writer File::Binary

Problems Specification was wrong –Required experimentation Very few knowledgeable people –NDAs –Lack of community Text representation libswf very unstable –Author unavailable

Future Work Text replacement Interface Object with SWF generation library More Input/Output filters –XML –SVG

Design Evaluation Structure is sound Perl was appropriate –good support from user base –hundreds of pre-built libraries –performance issues

Applications Broadband access: richer interfaces Database driven flash websites batch generation library for flash authoring application

Conclusions A lot has been achieved –but things still to do Interest from industry and community Many real-world applications Development will continue