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Stefan Westerfeld
audiowmark
Commits
2f0d1066
Commit
2f0d1066
authored
Feb 10, 2019
by
Stefan Westerfeld
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Small doc fixes.
Signed-off-by:
Stefan Westerfeld
<
stefan@space.twc.de
>
parent
48db5bd2
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2f0d1066
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@@ -8,15 +8,16 @@ watermark in the output sound file. For human listeners, the files typically
sound the same.
However, the 128-bit message can be retrieved from the output sound file. Our
tests show, that even if the file is converted to mp3 or ogg (with bitrate
s
higher than 128 kbit/s), the watermark usually can be retrieved without
pro
blems. The process of retrieving the message does not need the original
audio file (blind
decoding).
tests show, that even if the file is converted to mp3 or ogg (with bitrate
128
kbit/s or higher), the watermark usually can be retrieved without problems. The
pro
cess of retrieving the message does not need the original audio file (blind
decoding).
Internally, audiowmark is using the patchwork algorithm to hide the data in the
spectrum of the audio file. Some pseoudo-randomly selected amplitudes of the
frequency bands of a 1024-value FFTs are increased or decreased slightly, which
can be detected later. The algorithm used here is inspired by
spectrum of the audio file. The signal is split into 1024 sample frames. For
each frame, some pseoudo-randomly selected amplitudes of the frequency bands of
a 1024-value FFTs are increased or decreased slightly, which can be detected
later. The algorithm used here is inspired by
Martin Steinebach: Digitale Wasserzeichen für Audiodaten.
Darmstadt University of Technology 2004, ISBN 3-8322-2507-2
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@@ -56,8 +57,8 @@ and can be used for the add/get commands as follows:
The watermark strength parameter affects how much the watermarking algorithm
modifies the input signal. A stronger watermark is more audible, but also more
robust against modifications. The default strength is 10. A watermark with that
strength is recoverable after mp3/ogg encoding with 128kbit/s
. In our informal
listening tests, this setting also has a very good subjective quality.
strength is recoverable after mp3/ogg encoding with 128kbit/s
or higher. In our
informal
listening tests, this setting also has a very good subjective quality.
A higher strength (for instance 15) would be helpful for instance if robustness
against multiple conversions or conversions to low bit rates (i.e. 64kbit/s) is
...
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