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cocojumbo
Member
I'm trying to play an audio file and pitching it half down, but I would also like that the lenght of the audio does not change.
[[SimpleAudioEngine sharedEngine] playEffect:@"sample.wav" pitch:0.5 pan:0 gain:1];
This doesn't help because audio file is playing longer and the effect is not what I want.
How can I pitch audio file without affecting it's lenght?
Do you need to change the pitch dynamically in real time or do you always want to play this sound sample at this desired pitch? If the latter, how about loading your audio sample file into a program like Audacity which will have a pitch shifting algorithm which preserves the duration of the original file. You can change your pitch and resave it and now it will play back at the desired pitch in Cocos Denshion.
What you are originally asking for might be too computationally intensive for realtime playback, Steve Oldmeadow could probably enlighten on this.
Steve Oldmeadow
Administrator
You can't do what you want with CocosDenshion. Have a look at fmod or you could try rolling your own solution based on http://www.surina.net/soundtouch/
However, as David994A pointed out - real time time stretching is computationally expensive. If you are always going to play back the sample at half pitch then you are much better off processing the sample offline in something like Audacity or Sound Forge.
cocojumbo
Member
My point was to change audio dynamically in real time. Like SonicVox app (http://www.smule.com/sonicvox).
I installed fmod and tried some examples, however I didn't find any example of pitching audio.
Surina seems to do exactly what I need, however I don't know how to implement this in iPhone app.
Well, I thought this would be easier to do. I guess I don't have enough knowledge yet.
But thank you for answers!
Hi CocoJumbo,
I know this is an old thread, but I'm trying to do the same thing (pitch change dynamically without duration change). Did you have any luck with getting Sound Touch working on the iPhone? My reading indicates other people have used that or OpenAL. I will also look into fmod, Steve.
Thanks!
You can cheat by getting a sample which is of acceptable length at the highest pitch you want to play it at, and then using an OpenAL based implementation to play at a different pitch, cutting off the sound manually. The sound will get a bit weird as the pitch deviates further and further from the original sample (but this would happen with a realtime processing system as well).
What most synths do is start with a bunch of samples, spread out in pitch to have 1-2 samples per octave. The synth program then chooses one of those samples to play based on whichever is the closest to the pitch it wants to play at, and then plays that sample with a modified pitch for the "fine tuning".
Steve Oldmeadow
Administrator
@davecom - check this site out, http://www.dspdimension.com/
They have a free pitch shifting library for iPhone as well as some great tutorials on how to do pitch shifting.
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