[vorbis-dev] Difference between compressed & uncompressed audio?

[Ingo Saitz]

On Mon, Jan 01, 2001 at 05:33:48AM +0100, Aleksandar Dovnikovic wrote:
> I would like is someone could give me a few hints on how to
> distinguish whether a WAV file is uncompressed or it was
> created by decompressing mp3 file - I usually could take a
> look at the file through Sound Forge and look if there is a
> freq. cut-off (usually above 16kHz) or if there isn't one -
> then I can easily tell by listening if there are high-frequency
> artifacts (common for mp3). Is there any other way?

If you are talking about ripped CD tracks, there is another way
which might succeed, too. You just have to look at the length of
the wav file.

After substracting the 44 byte wav header, all ripped CD tracks
are a multiply of 2352, which is the blocksize for audio CDs. For
MP3 files you get a multiply of 4608 bytes (1152 samples). I
don't know if the latter value is always correct using different
decoders.

    Ingo

-- 
16                      Hard coded constant for amount of room allowed for
                        cache align and faster forwarding (tunable)

-- seen in /usr/src/linux-2.2.14/net/TUNABLE

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