Mixing 2 sounds from ByteArray

Question

I created a mixer and saved the entire sequence in an array and then played it again, now I want to save the mix as MP3, I was looking for a way to save the mix and the answer is to download it sounds like byteArrays (sound.extract) I have it, but I don’t know how to store all sounds in only one ByteArray, to save it as MP3, I received this code, for example, downloading 2 audio files and storing them in a separate ByteArrays and playing every sound, does anyone know how to store 2 byte item in one?

var mySound:Sound = new Sound(); var sourceSnd:Sound = new Sound(); var urlReq:URLRequest = new URLRequest("Track1.mp3"); sourceSnd.load(urlReq); sourceSnd.addEventListener(Event.COMPLETE, loaded); function loaded(event:Event):void { mySound.addEventListener(SampleDataEvent.SAMPLE_DATA, processSound); //mySound.play(); } var mySound2:Sound = new Sound(); var sourceSnd2:Sound = new Sound(); var urlReq2:URLRequest = new URLRequest("Track2.mp3"); sourceSnd2.load(urlReq2); sourceSnd2.addEventListener(Event.COMPLETE, loaded2); function loaded2(event:Event):void { mySound2.addEventListener(SampleDataEvent.SAMPLE_DATA, processSound2); mySound2.play(); mySound.play(); } function processSound(event:SampleDataEvent):void { var bytes:ByteArray = new ByteArray(); sourceSnd.extract(bytes, 8192); event.data.writeBytes(bytes); } function processSound2(event:SampleDataEvent):void { var bytes:ByteArray = new ByteArray(); sourceSnd2.extract(bytes, 8192); event.data.writeBytes(bytes); } 

Answer 1

I worked on a similar system for a while, I will do my best to give you some direction:

Your sample code does not actually mix MP3s - it creates 2 more sounds to play downloaded MP3s through SampleDataEvent. What you need to do is create only one “output” sound file that will hold / play the resulting mixed sound. You can easily save this data as it happens, and subsequently save this file as a new WAV / MP3 / what-have-you.

real / psuedo-code (read: lazy):

 output = new Sound(); output.addEventListener( SampleDataEvent.SAMPLE_DATA , mixAudio ); song1 = new Sound / load the first mp3 song2 = new Sound / load the second mp3 // a byteArray for "recording" the output and subsequent file creation recordedBytes = new ByteArray(); 

either wait until both mp3s are fully loaded, or run the input frame to determine when both sounds are no longer buffered (Sound.isBuffering)

when mp3 is ready:

 // numbers to store some values var left1:Number; var right1:Number; var left2:Number; var right2:Number; // bytearrays for extracting and mixing var bytes1:ByteArray = new ByteArray( ); var bytes2:ByteArray = new ByteArray( ); // start the show output.play(); function mixAudio( e:SampleDataEvent ):void{ //set bytearray positions to 0 bytes1.position = 0; bytes2.position = 0; //extract song1.extract( bytes1, 8192 ); song2.extract( bytes2, 8192 ); // reset bytearray positions to 0 for reading the floats bytes1.position = 0; bytes2.position = 0; // run through all the bytes/floats var b:int = 0; while( b < 8192 ){ left1 = bytes1.readFloat(); // gets "left" signal right1 = bytes1.readFloat(); // gets "right" signal left2 = bytes2.readFloat(); right2 = bytes2.readFloat(); // mix! var newLeft:Number = ( left1 + left2 ) * .5; var newRight:Number = ( right1 + right2 ) * .5; // write the new stuff to the output sound's e.data.writeFloat( newLeft ); e.data.writeFloat( newRight ); // write numbers to the "recording" byteArray recordedBytes.writeFloat( newLeft ); recordedBytes.writeFloat( newRight ); b++; } } 

Yes - you should really limit the possible output to -1/1. Do it. This is not highly optimized!

Ok so the easy part! The hard part really converts the final byteArray to MP3. Sound exists in Flash as PCM / uncompressed data, MP3 is obviously a compressed format. This "answer" is already too long, and I gathered all this information from several very smart people.

You can easily adapt "MicRecorder" to a universal sound recorder: http://www.bytearray.org/?p=1858

converting to MP3 will be a bitch: Thibault has another record on ByteArray.org - search for LAME MP3.

Great example / resource: http://www.anttikupila.com/flash/soundfx-out-of-the-box-audio-filters-with-actionscript-3/

Check out the open source André Michel project "Tonfall" in Google code.

Check out Kevin Goldsmith's blog and lab - he got a great example of using Pixel Bender with all this frenzy.

hope this helps!

PS - taking a replica from Andre, the optimal length of the sound buffer should be 3072. Try it on your computer!

Answer 2

If I understand your question correctly, you need to read the floating point data for each sample, summarize them and write the resulting value to a new audio stream. This would give a 50/50 mixture.

I don’t have access to the machine with the compiler right now, but it should be something like this (if bytes1 and bytes2 are two ByteArray objects of equal length):

 for (int bcnt = bytes1.size(); bcnt; bcnt--) bytes1.setByte(bcnt - 1, bytes2.getByte(bcnt - 1) + bytes1.getByte(bcnt - 1)); 

Of course, you probably want to do some overflow checking, but that should be enough to get you on the right track.

Answer 3

If you have uncompressed sound, you can simply add the values ​​of the individual elements of the array to the ByteArray . But you should also handle the limit for max / min values ​​(no overflow). Pretty sure there is nothing equivalent to mixing MP3 files, so you may have to decode, mix and encode to MP3 again.