Vorbis dev - Dec 2000 - Difference between compressed & uncompressed audio?

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?

Greetings,
Aleksandar

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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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> 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?
Hi
You can see that in Cool edit pro / spectral view or Frequency analysis
I can tell up to 256 kbps if there was a mp3 compression/decompression very
easy.
And JS is usually better than S at this test.
At 320 kbps mp3 I couldn't tell the difference.

Do I hear the difference?
I guess not. But I see it !!!

I hope Vorbis will soon have some kind of channel coupling. A good one.
Maybe at frequency band level rather than on a frame level.
Then it might be better than mp3 in every aspect.

How is beta 4 going? When will it be ready?

Happy 2001

Rajko

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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 MP3 co/dec cycle was stable enough (I doubt that:) you could check
by encoding and decoding the WAV (i.e. passing it through the psycho-
acoustics again) and check if it changes much.  An original file is
supposed to change much more than an ex-mp3 file (which already has
things masked out).


-- 
Beni Cherniavsky <cben@crosswinds.net>
                 (also scben@t2,cben@tx in Technion)

  No, No! You're not thinking; you're just being logical.
                                             - Niels Bohr

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