MP3 Duration about minimp3

[tosone]

No, minimp3 just for decode mp3. But this repo can get all kinds of files' duration.

[lieff]

In general case all file must be parsed to calculate the duration.
You can use mp3dec_iterate/mp3dec_iterate_buf to iterate through all frames and analyse headers using hdr_frame_samples().
Even in this case fast parser method can produce slightly incorrect result in case if not all frames are decodable (this is normal situation for cut`ed mp3's with not decodable start frame(s)).
But if we know that mp3 file is CBR, all frames are decodable and no padding - then duration calculation is trivial. Then we only need to analyse first frame, calc nframes=file_size/first_frame_size, calc samples=nframes*hdr_frame_samples(first_header) and calc duration from samples.