The next BASSenc release will include support for CoreAudio codecs on OSX and iOS. If you would like to try it now, the current build has been added to the iOS package (see 1st post). An updated BASSENC.H header is provided, which includes a BASS_Encode_StartCAFile function that accepts a file type (kAudioFileXXX), audio type (kAudioFormatXXX), and output filename. It also accepts a bitrate (bits per second), but that only applies to lossy formats like AAC (use "0" for the default bitrate).
For example, to create an ALAC M4A file, you could do this...
BASS_Encode_StartCAFile(handle, 'm4af', 'alac', 0, 0, filename);
Or for an IMA4/ADPCM CAF file...
BASS_Encode_StartCAFile(handle, 'caff', 'ima4', 0, 0, filename);
The "flags" parameter accepts BASS_ENCODE_FP_xxx, BASS_ENCODE_PAUSE, BASS_ENCODE_AUTOFREE, BASS_UNICODE, and a new BASS_ENCODE_MONO flag to convert the source data to mono (if it isn't already). Use BASS_Encode_Stop to close the encoder/file.