Question

I’m making an opengl game for iPhone. And I’m about to start adding sound effects to the app. I wonder what’s the best framework for this purpose.

Is AV foundation my best option? Any others I’m missing, like Open AL perhaps?

Answer 1

General strength/weakness summary of iPhone sound APIs from a game perspective:

• AVFoundation: plays long compressed files. No low-level access, high latency. Good for theme song or background music. Bad for short-lived effects.
• System sounds: plays short (think 0-5 sec) sounds. Must be PCM or IMA4 in .aif, .wav, or .caf. Fire-and-forget (can’t stop it once it starts). C-based API. Appropriate for short sound effects (taps, clicks, bangs, crashes)
• OpenAL: 3D spatialized audio. API resembles OpenGL and is a natural accompaniment to it. Easy to mix multiple sources. Audio needs to be PCM (probably loaded by Core Audio’s “Audio File Services”). Pretty significant low-level access. Potentially very low latency.
• Audio Queue: stream playback from a source you provide (reading from file, from network, software synthesis, etc.). C-based. Can be fairly low-latency. Not really ideal for a lot of game tasks: background music is better suited to AVFoundation, shorter sounds to system sounds, and mixing to OpenAL or Audio Units. Can record from mic.
• Audio Units: lowest public level of Core Audio. Extremely low latency (< 30 ms). C, and hard-core C at that. Everything must be PCM. Multi-channel mixer unit lets you mix sources. Can record.

Be sure you set up your audio session appropriately, meaning you declare a category that indicates how you interact with the rest of audio on the device (allow/disallow iPod playback in the background, honor/ignore ring/silent switch, etc.). AV Foundation has the Obj-C version of this, and Core Audio has somewhat more powerful equivalents.