XML based swf, swc and abc assembler written in haXe.
(Available in as3, haxe, neko, cpp, php, javascript, xml)

Try it online at the bottom of this page.

LIB example: (zip)

<lib>
        <bitmapdata file="haxe.png" class="MyBitmapData"/>
        <bitmap file="haxe.png" class="MyBitmap"/>
        <sprite file="haxe.png" class="MySprite"/>
        <movieclip file="haxe.png" class="MyMovieClip"/>
        <button file="haxe.png" class="MySimpleButton"/>
        <bytearray file="haxe.png" class="MyByteArray"/>
        <sound file="chopin.mp3" class="MySound"/>
        <font file="chopin.ttf" class="MyFont" glyphs="32-125"/>
</lib>

> hxswfml xml2lib library.xml library.swf

SWF example: (zip)

<swf>
        <SetBackgroundColor color="0xFFFFFF" />
        <DefineShape id="1" >
                <BeginFill color="0x000000" alpha="1.0" />
                <DrawRect x="0" y="0" width="100" height="100" />
        </DefineShape>
        <PlaceObject id="1" depth="1" />
        <ShowFrame/>
</swf>

> hxswfml xml2swf index.xml index.swf

ABC example: (zip)

<abcfile>
        <class name="Main" extends="flash.display.MovieClip" >
                <var name="nr" type="int" value="100" />
                <function name="Main" args="" return="void" >
                        <OFindPropStrict v="trace" />
                        <OThis/>
                        <OGetProp v="nr"/>
                        <OCallPropVoid v="trace" nargs="1" />
                        <ORetVoid />
                </function>
        </class>
</abcfile>

> hxswfml abc2swf abc.xml index.swf -main Main

Binaries are available for:

Flash (swf, swc)
Air (swc)
Cpp (exe)
NekoVM (n, exe)

Source is available in:

as3
haxe
neko
cpp
php
javascript
xml

Commands in commandline versions:

xml2swf
xml2lib
xml2swc
xml2abc
abc2swf
abc2swc
abc2xml
abc2hxm
xml2hxm
ttf2swf
ttf2hx
ttf2path
flv2swf

LIB: XML Schema:

<lib version="10" width="800" height="600" fps="30" backgroundcolor="0xffffff" frameCount="1" actionscript3="true" compressed="false" useDirectBlit="false" useGPU="false" hasMetaData="false" useNetWork="false" >
        <!-- flash.display.BitmapData -->
        <bitmapdata file="*.gif,jpg,png" link/class="MyBitmapData"/>
        
        <!-- flash.display.Bitmap -->
        <bitmap file="*.gif,jpg,png" link/class="MyBitmap"/>
        
        <!-- flash.display.Sprite -->
        <sprite file="*.gif,jpg,png" link/class="MySprite"/>
        
        <!-- flash.display.MovieClip -->
        <movieclip file="*.gif,jpg,png" link/class="MyMovieClip"/>
        
        <!-- flash.display.SimpleButton -->
        <button file="*.gif,jpg,png" link/class="MySimpleButton"/>
        
        <!-- flash.utils.ByteArray -->
        <bytearray file="*.*" link/class="MyByteArray"/>
        
        <!-- flash.media.Sound -->
        <sound file="*.mp3" link/class="MySound"/>
        
        <!-- flash.text.Font -->
        <font file="*.ttf,otf" link/class="MyFont" glyphs="32-125,200-255" name="Arial"/>
        
        <abc file="*.swf,abc" link="MyClass" />
</lib>

SWF: XML Schema:

<?xml version="1.0" ?>
<swf width="800" height="600" fps="30" version="10" compressed="true" frameCount="1" >
        
        <FileAttributes actionscript3="true" useNetwork="false" useDirectBlit="false" useGPU="false" hasMetaData="false" />
        
        <SetBackgroundColor color="0xFFFFFF" />
        
        <ScriptLimits maxRecursionDepth="256" scriptTimeoutSeconds="15" />

        <MetaData file="path/to/file/containing/rdf_metadata *.txt, *.xml" />
        
        <DefineBitsJPEG id="?" file="path/to/file *.jpg, *.png, *.gif" />
        
        <DefineBinaryData id="?" file="path/to/file *.any " />
        
        <DefineSound id="?" file="path/to/file *.mp3" />
        
        <DefineFont id="?" file="path/to/swf/containing/file *.swf, *.ttf", *.otf, charCodes="32-127" name="Arial"/>
        
        <DefineEditText id="?" initialText="" fontID="" useOutlines="false"  width="100" height="100" wordWrap="true" multiline="true" password="false" input="false" autoSize="false" selectable="false" border="false" wasStatic="false" html="false" fontClass="" fontHeight="12" textColor="0x000000" alpha="1.0" maxLength="0" align="0" leftMargin="0" rightMargin="0" indent="0" leading="0" variableName="" file="" />

        <DefineShape id="?" bitmapId="?" x="0" y="0" scaleX="1.0" scaleY="1.0" rotate0="0.0" rotate1="0" repeat="false" smooth="false" />
        
        <DefineShape id="?">
                <LineStyle width="0.0" color="0x000000" alpha="1.0" pixelHinting="false" scaleMode="none/horizontal/vertical" caps="round/square)" joints="round/bevel/miter)" miterLimit="0.0" noClose="false"/>
                <BeginFill color="0x000000" alpha="1.0" />
                <BeginBitmapFill bitmapId="?" x="?" y="?" scaleX="?" scaleY="?" rotate0="?" rotate1="?" repeat="false" smooth="false"/>
                <BeginGradientFill colors="?,?,?" alphas="?,?,?" ratios="?,?,?" x="?" y="?" scaleX="?" scaleY="?" rotate0="?" rotate1="?"/>
                <MoveTo x="0.0" y="0.0" />
                <LineTo x="0.0" y="0.0" />
                <CurveTo cx="0.0" cy="0.0" ax="0.0" ay="0.0" />
                <DrawCircle x="0.0" y="0.0" r="0.0" sections="16" />
                <DrawEllipse x="0.0" y="0.0" width="0.0" height="0.0" />
                <DrawRect x="0.0" y="0.0" width="0.0" height="0.0" />
                <DrawRoundRect x="0.0" y="0.0" width="0.0" height="0.0" r="0.0"/>
                <DrawRoundRectComplex x="0.0" y="0.0" width="0.0" height="0.0" rtl="0.0" rtr="0.0" rbl="0.0" rbr="0.0" />
                <EndLine />
                <EndFill />
        </DefineShape>

        <DefineSprite id="?" file="path/to/file/ *.flv">

        <DefineSprite id="?" frameCount="1">
                <PlaceObject id="?" depth="?" name="" move="false" x="0" y="0" scaleX="1.0" scaleY="1.0" rotate0="0.0" rotate1="0.0" />
                <RemoveObject depth="?" />
                <StartSound id="?" stop="false" loopCount="0" />
                <Custom tagId="?" file="path/to/file/containing/tagbody bytes" data="?" comment=""/>
                <FrameLabel name="?" anchor="false" />
                <Tween depth="?" frameCount="?"></Tween>
                <ShowFrame />
        </DefineSprite>
        
        <DefineButton id="?">
                <ButtonState id="?" depth="?" up="true" over="false" down="false"  hit="false" x="0" y="0" scaleX="1.0" scaleY="1.0" rotate0="0.0" rotate1="0.0" />
        </DefineButton>

        <DefineScalingGrid id="?" x="?" width="?" y="?" height="?" />

        <PlaceObject id="?" depth="?" name="" move="false" x="0" y="0" scaleX="1.0" scaleY="1.0" rotate0="0.0" rotate1="0.0" />
        
        <RemoveObject depth="?" />
        
        <StartSound id="?" stop="false" loopCount="0" />

        <FrameLabel name="?" anchor="false" />

        <Custom tagId="?" file="path/to/file/containing/tagbody bytes" data="?" comment=""/>

        <DefineABC (file="path/to/file/containing/abc.xml,.swf" isBoot="false")>
                <ABCfile>
                        <import name="?"/>
                        <class  name="?" extends="?" implements="" interface="false" sealed="false>
                                <var name="?" type="" value="" const="false" static="false" ns=""/>
                                <function  name="?" args="" return="*" kind="normal/get/set" static="false" final="false" variableArgs="false" defaultParameters="" locals="" argumentsDefined="false" override="false" ns="" native="false" usesDXNS="false" newBlock="false" unused="false" debugName="" maxStack="" maxScope="">
                                        <OThis />
                                        <OScope />
                                        <!-- opcodes* -->
                                        <ORetVoid />
                                </function>
                        </class>
                </ABCfile>
        </DefineABC >

        <SymbolClass id="?" class="?" base="" />

        <Tween depth="?" frameCount="?">
                <Tw prop="x/y/scaleX/scaleY/rotate0/rotate1" start="?" end="?" />
        </Tween>

        <ShowFrame count="1"/>
</swf>

*opcodes

ABC: XML Schema:

To run hxswfml.n you need the Neko VM which can be downloaded here:http://nekovm.org/download
To compile hxswfml from source you need the haXe compiler which can be downloaded here: http://haxe.org/download

See wiki for more info and also the examples.zip. It contains 50 to 100 examples which should explain most.
Linking classes to assets
SWFTags
SWF All examples(50MB):(zip)

Currently supported swf tags are:

fileAttributes
setBackgroundcolor
scriptLimits
metadata
defineBitsJpeg2
defineShape
defineShape2
defineShape3
defineShape4
defineSprite
defineButton
defineVideoStream
defineVideoFrame
defineFont
defineFont2
defineFont3
defineFont4
defineEdittext
defineAbc
defineScalinggrid
defineSound
soundStreamHead2
soundStreamBlock
placeObject
placeObject2
removeObject
removeObject2
startSound
symbolClass
exportAssets
frameLabel
showFrame
endFrame
custom
tween

Links to additional information about the used swf tags:
SWF File Format Specification (Version 10) : http://www.adobe.com/devnet/swf/

swfheader 1 3
fileattributes 1
setbackgroundcolor 1 2 3
scriptlimits 1
metadata 1

definebitsjpeg 1 2
defineshape 1 2 3
definesprite 1 2 3
definebutton 1 2 3
definebinarydata 1
definesound 1 2
definefont 1 2 3
defineedittext 1 2 3
defineabc 1
definescalinggrid 1

placeobject 1 2 3
removeobject 1 2 3
startsound 1 2
tween

symbolclass 1

framelabel 1 2 3
showframe 1 2 3
endframe 1 2 3

swf lib example application

The purpose of this application is similar to "export in first frame" for library assets in the Flash IDE or similar to what you would accomplish with swfmill or the '['Embed']' tag for the Flex SDK (mxmlc).

Note:
Embedded flash apps in google code wiki pages can behave erratically.
If you are experiencing unexpected behaviour you can test it in this regular web page: swf lib example application

Instructions:

Click the 'Add Files' button
Edit the class name and choose a base class
Click the icon left of the file name (and then click the silver bar at the bottom of the popup or click the zip-button) to see an example of how to use the output swf.
Click the 'Publish' button

Notes:

The 'Settings' button is a toggle button, click it again to leave the settings menu.
Clicking the icon will show the content of your asset. Click the bar at the bottom to toggle between source code and content. You can publish an swc or swf with the individually exported asset. This swf or swc is not intented to be run but to be linked (in)to your project. The zip output contains a haxe script besides the swf showing how to do this.
This flash app uses hxswfml internally. You can use hxswfml.swc for coding in AS3 or use the haxe source files in case you code in haxe.