Flexible output formats for AudioFileWriter

[alexbw]

Right now, only writes to MP4. Should be able to specify any output format available

[coryalder]

A note on this subject. Manually changing the output format to mp3 like so:

AudioFileWriter.mm: 87

AudioStreamBasicDescription outputFileDesc = {44100.0, kAudioFormatMPEGLayer3, 0, 0, 1024, 0, 2, 0, 0};
CheckError(ExtAudioFileCreateWithURL(audioFileRef, kAudioFileMP3Type, &outputFileDesc, NULL, 0, &_outputFile), "Creating file");

Seems to be producing corrupted files. They won't open in QuickTime Player on my Mac. Not sure what's happening, but I thought I'd mention it since there was already an open issue on the subject.

Edit: oh, apparently iOS doesn't have a built in mp3 encoder? (http://stackoverflow.com/questions/6179481/audiostreambasicdescription-for-mp3)

Edit 2: yup. my mistake: (https://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/MultimediaPG/UsingAudio/UsingAudio.html#//apple_ref/doc/uid/TP40009767-CH2 table 1-2).

[alexbw]

This is not a thing I anticipate that I will be doing, unfortunately