[vorbis-dev] hlp: off topic but need experty---How to calculate amplitute of l eaner pcm data

[Jonathan_Huang at compal.com]

To vorbis expert group:

        Sorry to drop this message but I need help :-(
        I got the linear pcm data from windows waveio api or vorbis codec. I
think the data is signed. My goal is to construct a db scale(ppm) to display
the volume while playing just like the old tape deck.
        The original amplitude is expressed in turn of voltage. I have no
idea how to coverted it in digital form. 
I saw a formula like p= 1/n * sum(x=0 to n) (pcmvalue/2 to power of (num of
bits))^2 and signal level L=10 log p + C.  
I also noted I need to add a constant for a or mu law coded pcm. Do I need
to add any for linear pcm? How do I convert this to peak power meter or this
is it?
        Please let me know if there is a place I can ask or find more
relative data.

John

-----Original Message-----
From: Anna_Zhavor at abbyy.com [mailto:Anna_Zhavor at abbyy.com] 
Sent: Monday, October 06, 2003 7:52 PM
To: vorbis-dev at xiph.org
Subject: [vorbis-dev] Question about distribution Vorbis software

Dear Sirs,
we should like to use your software for compression our sound files. 
We use the following dlls:
        ogg.dll, 
        vorbis.dll,
        vorbisenc.dll,
        vorbisfile.dll

We will insert your copyright "Copyright (c) 2003, Xiph.org Foundation" in
the
documentations of our software and the following text in our End-User
License Agreement:

"THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."

Is it enough?

Thank you,
Anna Zhavoronkova,
Lingvo product manager,
ABBYY Software

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