Audio processing. Is it possible to directly access the decoded audio data going into the analog input of a computer
A program to convert an .mp3 audio file-format into , say, an .ra (real audio) audio file-format needs fully to decode the mp3 file into raw waveform audio and then re-encode it into its new format. 

This raw audio waveform data can be contained within 32/64-bit floating point or some integer formats though. But when it's sent to audio DAC, it should be in an integer format; this depends on the PC audio standard and as far as I know, Windows (and like) systems use 8/16 bit integer formats at this stage (you have to check for their developer knowledge base for their latest implementations) 

So there can be a very slight difference between the raw data at the input buffer of DAC and raw data that reside in the system RAM, but they are both raw waveform data.

Nevertheless, unless the the two audio formats have some common design layering, then it's not possible to transcode from one format to the other without full decoding of the original. 

Finally, analog audio is practically never required as it would introduce more errors and complexities than do anything useful.