iphone, objective c, how to read raw data from audio file (without codec applied)

I am developing an iphone app, which sends/receives data to audio/headphone jack of iphone. I assume we can send/receive data to hea开发者_运维知识库dphone jack but that data is audio file with some codec applied. I want to read an audio file and send raw data to headphone jack.. How can i do that..? Any help or code snippet appreciated. Best regards, Abdul Qavi

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Since the headphone jack is on the other side of a couple of D>A converters, I guess you'd need a codec that converts to modem tones. Hope you files are really small 'cos transfer rate would be pretty slow, even if you could figure out how to use both channels.

Just 'tooth 'em.

Rgds, Martin