I find myself porting an old multimedia title to iOS/OSX and I'm somewhat disappointed with the quality of audio output I've achieved via OpenAL, in that it's got that "scratchy" quality one hears when PCM is resampled poorly. However, I'm feeding it 8-bit PCM at 11025KHz and I do believe the native rate is 44100KHz so I can't imagine why anything other than a 1:4 integral expansion of the samples would be occurring. The sound itself is very clean when played back on a Win32 system so I know there's no problems with the data itself. Nor are there any buffering problems in that I'm keeping about 32K buffered ahead of the playback position. But the sound quality just isn't that good. Has anyone else encountered this and are there configuration options to work around it? I've gone through the docs and nothing seems applicable to the problem ...
iOS doesn't handle 8-bit data very well. Try converting it to 16-bit.
afconvert -f caff -d LEI16@11025 sourcefile.wav destfile.caf
You could also compress it to mp3 or aac, but that's a little more complicated to load since it needs to be converted to 16-bit little endian format when loaded.
Here's a loader that handles any 16-bit audio format: https://github.com/kstenerud/ObjectAL-for-iPhone/blob/master/ObjectAL/ObjectAL/Support/OALAudioFile.m