obtain sample frame offset corresponding to certain time in audio file-iPhone

Given an audio file of duration 10s, if I want to seek to 2s, how do I obtain the s开发者_StackOverflow社区ample frame offset?

if it's LPCM (e.g. not compressed), then use the sample rate.

in pseudocode:

double sampleRate = audioFile.getSampleRate();
size_t offsetInSeconds = 2;
size_t sampleToRead = sampleRate * offsetInSeconds * audioFile.getChannelCount();
AudioSample sample = audioFile.getSampleAt(sampleToRead);