I suppose it depends on what type of ‘change’ you are referring to. One can down-sample, in which case you are changing the sampling frequency for encoding and decoding. There is then a change to audio quality, but no change to pitch.
Another situation is when the playback (decoding) frequency is set different than the true (encoded) sampling frequency. This alters the playback time and the pitch.
FMOD’s ‘rate’ function (I think it’s a Channel operation) can be used to change the playback frequency. To resample, you could lock an FMOD sample (to access an array of decoded pcm data) and then pass the data to a suitable re-sampler; there’s a free conversion library called R8B.DLL that can do this.
If I’m not mistaken, CoolEdit has some operation that can be used to alter the media duration with negligible effects on pitch. Just remember, the closer your task gets to “editing,” the more difficult it is to implement the process with FMOD. Brett often has to remind us that FMOD was designed for playback, not editing.
[Brett, if you’re reading this, PLEASE re-consider adding one more feature to FMOD 3.x: something equivalent to ReadData in FMOD Ex (i.e., a useful method to decode and access contiguous chunks of pcm data from compressed sound files that are too large to open/decode at all once).]
- Anonymous answered 14 years ago
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