Is it possible to layer two background music tracks? ($50 reward)

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Is it possible to layer two background music tracks? ($50 reward)

(5 posts) (4 voices)

Started 2 years ago by michaelhighland
Latest reply from Steve Oldmeadow

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michaelhighland
Member

I am hoping to layer two synchronized background music tracks for a game, a basic track, and a secondary melody for when the player gets a power-up. The tracks would be the same length, and would likely both always be playing, then the volume of the secondary track based on the game state.

Has anyone attempted anything like this? I've been searching everywhere for an example of how to attempt this, but haven't turned up anything.

I'm willing to mail the first person who can provide some specific help on this challenge $50.

Thanks!
-Michael

Posted 2 years ago #
jd
Member

You can only play one track using hardware acceleration at a time. Otherwise you can play up to 32 sounds simultaneously using CocosDenshion.

Also, you don't have to offer money for knowledge here. We have a very helpful community and it's free.

Posted 2 years ago #
michaelhighland
Member

Haha, thanks - I just thought some reward might inspire faster responses :) Does anyone have any thoughts on working around the 1 track limit or is it just impossible? What if the background track was treated as a sound effect rather than a background track? Can two sound effects be synchronized to play together and loop?

Posted 2 years ago #
rod
Member

You can play multiple tracks (compressed, uncompressed, or both) at the same time, but as @jd mentioned only one will be hardware decoded. The first compressed track (mp3, etc) that you start to play will be hardware decoded, all the others will be software decoded (taking up some of your CPU cycles). Take care not to play a mp3 sound effect first and then the mp3 background track while the sound sfx is playing, as once a track/sound starts on the software decoder, it stays there even if the hardware decoder frees up.

Uncompressed (wav/AIFF) files don't have the CPU penalty, but having WAVs for your background track would make for a large app.

You could have your basic track as the background music and then play the second melody as a sound effect. If it is used only once in the level, you can even unload the second track from memory after playing it. You can have sound effects in mp3 format by the way (not optimal, but you can).

Does that help any?

Posted 2 years ago #
Steve Oldmeadow
Administrator

The problem is synchronising the tracks. If you look at Apple's audio guidelines they recommend using Audio Queue Services if you need to synchronise audio which is a lower level API than the one's used in CocosDenshion (AVAudioPlayer and OpenAL).

You could kick off two AVAudioPlayers but there is no guarantee that they will start within a reasonable time limit for a musical application. Also don't forget software decoding of compressed audio is only supported on 3.x OS, if you want to support older operating systems you can't use that approach.

You can play two looped sound effects and if the sounds have been preloaded then they will start within nanoseconds of each other which is fine for a musical application. However, this is only suitable for synchronising the playback if both files are started at the same time. You could not do something like start an effect playing at a musically significant interval such as the start of the 33rd bar of another audio source.

Lots of people that want to do what you require use the fmod sound engine. The downside is that it costs US$500 per commercial iPhone app. If your app is going to be free and without advertising then you can use fmod for free and that would definitely be the way to go.

Posted 2 years ago #

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