Does all audio format has a header for message length

Does all audio format has a header for audio length (in second)? If not, what kind of audio format has that i开发者_如何学Gonformation embedded in the header.

Thank you.

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Not necessarily. Typical wav files will have a wave format chunk (WAVEFORMATEX if you're coding on Windows) which contains the sample rate and number of bits per sample. Most of the WAV files you'll tend to come across are in PCM format where you know that there is always the same number of samples per second and bits per sample, so from the size of the file and these values you can work out the duration exactly.

There are other types of WAV file though which may be compressed (though these are much rarer) and for those you'll need to use the 'average bytes/sec' field of the WAVE header to work out the length.

If you're using AIFF (largely used on macs) then this has similar data members in the header.

Getting the length from an MP3 file is more difficult -- some suggestions are in this other question