从许多其他音频文件（混音器）在iPhone / iPad上创建音频文件

Question

I am trying to create something similar like Piano app on the iPhone. When people tap a key, it play a piano note. Basically, there will have only 7 notes (C) at the moment. Each note is a .caf file and its length is 5 seconds.

I do not know if there is any way to save the song user played and export to mp3/caf format? The AVAudioRecord seems only record from the microphone input.

Many thanks

Answer 1

For such an app you probably don't want to record into an audio-file - instead record the note-presses and timings for a much more compact format and then play back the same as if the user was pressing the notes at the recorded times.

If you do want to be able to export an audio file format then you can write a simple mixer which adds together the individual samples from your source samples with the correct offsets and puts the results in your output audio buffer. You should probably also write a very simple compressor so that you keep the sample volume without any distortion caused by 'clipping'. This can be done by dividing down any summed sample above 95% of the maximum sample value. There may also be a way to use OpenAL to do this mixing for you and play back into an audio buffer.