I’ve continued building on http://blog.andre-michelle.com/2010/playback-mp3-loop-gapless/ . And I’ve come up with some improvements:

• make the loop a separate class
• allow switching from one loop to another seamlessly.
• fix a bug that what harmless in a browser but that broke the app on an iphone. In certain cases the previous “extract” method would read beyond the buffer causing the looping to stop.

See below for the code.

I apologize for the formatting, just copy and paste it and you should be able to read it properly.

To use it you still need to calculate the number of samples (see previous post).

For example:

const out: Sound = new Sound(); // Use for output stream

var loop:Mp3Loop = new Mp3Loop(out);

loop.loadMp3(“yourloop.mp3″, 213120l);

package
{
import flash.events.Event;
import flash.events.IOErrorEvent;
import flash.events.MouseEvent;
import flash.events.ProgressEvent;
import flash.events.SampleDataEvent;
import flash.media.Sound;
import flash.net.URLRequest;
import flash.utils.ByteArray;

public class Mp3Loop
{
private const MAGIC_DELAY:Number = 2257.0; // LAME 3.98.2 + flash.media.Sound Delay

private const BUFFER_SIZE: int = 4096; // Stable playback
// Use for decoding
private var _activeMp3: Sound;
private var _inactiveMp3: Sound;
private var _inactiveMp3SamplesTotal:uint;
private var _activeMp3SamplesTotal:uint;

// Use for output stream
private var _out: Sound;

private var _samplesPosition: int = 0;

private var _swapPending:Boolean;

private var _isPlaying:Boolean;

public function Mp3Loop(outputSound:Sound)
{
_out = outputSound;
_out.addEventListener( SampleDataEvent.SAMPLE_DATA, sampleData );
_out.play();

}

public function loadMp3(url:String, samplesTotal:uint):void{
_inactiveMp3SamplesTotal = samplesTotal;
_inactiveMp3 = new Sound();
_inactiveMp3.addEventListener( Event.COMPLETE, mp3Loaded, false, 0, true );
_inactiveMp3.addEventListener( IOErrorEvent.IO_ERROR, mp3Error, false, 0, true );
_inactiveMp3.load( new URLRequest(url) );

}

private function swap():void{

_swapPending = false;
_activeMp3 = _inactiveMp3;
_inactiveMp3 = null;
_activeMp3SamplesTotal = _inactiveMp3SamplesTotal;
_inactiveMp3SamplesTotal = 0;

}

private function mp3Loaded( event:Event ):void
{

if(!_isPlaying){
swap();
_isPlaying = true;
}else{
//loop is playing, wait for end
_swapPending = true;
}

}

private function sampleData( event:SampleDataEvent ):void
{
if(_isPlaying )
{
extract( event.data, BUFFER_SIZE );
}
else
{
silent( event.data, BUFFER_SIZE );
}
}

/**
* This methods extracts audio data from the mp3 and wraps it automatically with respect to encoder delay
*
* @param target The ByteArray where to write the audio data
* @param length The amount of samples to be read
*/
private function extract( target: ByteArray, length:int ):void
{
while( 0 < length )
{
if( _samplesPosition + length + MAGIC_DELAY > _activeMp3SamplesTotal )
{
var read: int = _activeMp3SamplesTotal - _samplesPosition - MAGIC_DELAY;

_activeMp3.extract( target, read, _samplesPosition + MAGIC_DELAY );

_samplesPosition += read;

length -= read;

}
else
{
_activeMp3.extract( target, length, _samplesPosition + MAGIC_DELAY );

_samplesPosition += length;

length = 0;
}

if( _samplesPosition == _activeMp3SamplesTotal - MAGIC_DELAY) // END OF LOOP > WRAP
{
_samplesPosition = 0;
if(_swapPending){
swap();
}
}
}
}

private function silent( target:ByteArray, length:int ):void
{
target.position = 0;

while( length-- )
{
target.writeFloat( 0.0 );
target.writeFloat( 0.0 );
}
}

private function mp3Error( event:IOErrorEvent ):void
{
trace( event );
}

public function get isPlaying():Boolean
{
return _isPlaying;
}

public function stop():void{
_inactiveMp3 = _activeMp3 = null;
_inactiveMp3SamplesTotal = _activeMp3SamplesTotal = 0;
_isPlaying = false;
_samplesPosition = 0;
}

}
}

The basic bricks you need for an ios only native extension are :

• an XCode project where you code your native functionality
• a Flash Builder Library project where you write the AS code that serves as a bridge

And then you would expect that you could point the Library project to your compiled native library, and it would produce a ANE file, ready to use. Right? Right? No.

You have to use a command line tool called ‘adt’, that comes with your AIR SDK. Fair enough. Along with a descriptor XML file. Up to there you grudgingly admit that this is new technology and that you have to put up with half-finished stuff, but where things fall to pieces is where you start dealing with the mysterious “library.swf”.

This is actually a swf that you must yourself manually extract from the swc. WTF Adobe, can’t your adt tool do this itself? So anyway: take a command line tool like 7zip and extract library.swf from your swc, and then use it in your command line. The doc mentions that the library.swf file can be different for each targeted platform. Really, I can’t what design would justify having different AS3 APIs for different platforms, but I’m new to this. Still seems harebrained though.

So after jumping through all the hoops, I ended up with the following error:

Unable to build a valid certificate chain for the signer.

Fear not, what the tutorials don’t tell you is that signing an ANE is optional! So if your signing fails, you can still use your ANE yourself, just remove the signing.

One last (bonus) hoop: The packaging settings are supposed to detect whether or not an ANE is used. At least in my test here it says it isn’t being used even if it, so don’t hesitate to tell Flash Builder to include the ANE anyway.

This article helped me the most, even if it’s for Android, not Ios.

http://www.adobe.com/devnet/air/articles/developing-native-extensions-air.html

So I worked with this example :

http://www.adobe.com/devnet/air/native-extensions-for-air/extensions/gyroscope.html

Below is my version of ./package.sh as mentioned in the article, in case it can help someone.

adt_directory=”/Applications/Adobe Flash Builder 4.6/sdks/4.6.0/bin”

root_directory=”/Users/arielsommeria-klein/Documents/workspaces/tests/Vibration/VibrationNEDeliverables”

library_directory=${root_directory}/VibrationActionScriptLibrary

native_directory=${root_directory}/VibrationiOSLibrary

#signing_options=”-storetype pkcs12 -keystore /Users/arielsommeria-klein/Documents/ios/certs/ariel-ios.p12″
dest_ANE=NetworkInfo.ane
extension_XML=${library_directory}/src/extension.xml
library_SWC=${library_directory}/bin/VibrationActionScriptLibrary.swc

“${adt_directory}”/adt -package -target ane “${dest_ANE}” “${extension_XML}” -swc “${library_SWC}” -platform iPhone-ARM -C “${native_directory}” .
#”${adt_directory}”/adt -package ${signing_options} -target ane “${dest_ANE}” “${extension_XML}” -swc “${library_SWC}” -platform iPhone-ARM -C “${native_directory}” .

The first thing you need is an uncompressed wave file (.wav) that contains a loop. Flash doesn’t support playback of wav files, so you need to convert it to a compressed format. You have two options here: mp3 or aac.

Mp3 has the advantage to be easy to use in Flash but unfortunately contains padding so looping it as is won’t go smoothly.

AAC can be use in Flash 10 and onwards with some trickery described here : http://www.adobe.com/devnet/flashplayer/articles/hd_video_flash_player.html. It has the advantage of not containing padding, so it loops almost perfectly. If that’s enough for you, then good. If not, read on.

If you need perfect, then this post has a pretty good method for it. http://blog.andre-michelle.com/2010/playback-mp3-loop-gapless/ It however does not tell you how to get one necessary information: the number of samples in your loop. If you encode using LAME with the command line (binaries here ), then it will tell you the number of frames. The number of samples per frame is constant with mp3s, it’s 1152. So total number of samples in loop = number of frames * 1152.

Finally, I found this approach to create a loopable mp3 interesting, but I didn’t use it : http://www.compuphase.com/mp3/mp3loops.htm

http://www.silexlabs.org/the-blog/amfphp-v2-reloaded-is-out/

the files:

http://sourceforge.net/projects/amfphp/files/amfphp/amfphp-2.0.zip/download

You define a path as a constant, and use it everywhere in your build paths. That way, when your colleague checks out the various projects, the only place that needs to be changed is that constant. To define such a constant, go to Flash Builder Preferences -> General -> Workspace -> Linked Resources. Add a constant, say WORKSPACE_ROOT = /Users/admin/Documents/workspace/, then use it in your project properties. For example to get a project to publish at /Users/admin/Documents/workspace/common, instead of putting that path in Flex Build Path -> Output Folder, you can put ${WORKSPACE_ROOT}/common. In this way, when you set up a workspace, you don’t have to dig through project preferences, but just need to set the Linked Resource.

download at sourceforge: http://sourceforge.net/projects/amfphp/files/amfphp/amfphp-2.0RC1.zip/download

The error router is a singleton that can be used to separate error generation from error display. Code generating an error can call ErrorRouter.getInstance().notifyError(errorData)
A visual object responsible for displaying error messages can implement IErrorDisplay and call ErrorRouter.getInstance().registerErrorDisplay(this)
If no error display is registered, a simple trace is used.

I’d post the code if posting code in wordpress wasn’t such a pain. You can download it though

http://arielsommeria.com/blog/content/error.zip

My slides, and a post about the evening, both in French:

http://www.silexlabs.org/the-blog/fr/2011/03/les-slides-de-la-presentation-amfphp/

http://www.silexlabs.org/the-blog/fr/2011/03/silex-labs-presente-amfphp-aux-tontons-flexeurs-review/