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The quantum of WAV file is a square wave. What is the quantum of a WMA file?

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Curious wrote:

> The quantum of WAV file is a square wave...

Where did that strange idea come from? For file formats, check out
http://www.wotsit.org/ and http://sox.sourceforge.net/AudioFormats.html.

What you don't know doesn't hurt much. The major trouble comes from the
the falsehoods you believe.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

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Curious wrote:
> 
> The quantum of WAV file is a square wave. 

No, the quantum of a WAV files is the unit impulse.

> What is the quantum of a WMA file?

WMA files decode to PCM audio which is what you have in standard
WAV files.

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo  n...@mega-nerd.com (Yes it's valid)
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Erik de Castro Lopo <n...@mega-nerd.com> wrote in message news:<4...@mega-nerd.com>...
> Curious wrote:
> > 
> > The quantum of WAV file is a square wave. 
> 
> No, the quantum of a WAV files is the unit impulse.
> 
> > What is the quantum of a WMA file?
> 
> WMA files decode to PCM audio which is what you have in standard
> WAV files.
> 
> Erik

Low-bitrate WMA files have a pleasant type of distortion to them.
Couldn't say the same about low-bitrate WAV files.

WMA "noise" tends to be musical while WAV "noise" tends to resemble
square-waves.

I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to
where it is just recognizable by WMA file, and then amplifying it back
to normal. The arftifacts are kinda interesting there.

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Curious wrote:
> 
> Low-bitrate WMA files have a pleasant type of distortion to them.
> Couldn't say the same about low-bitrate WAV files.
> 
> WMA "noise" tends to be musical while WAV "noise" tends to resemble
> square-waves.

??????????????
 
> I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to
> where it is just recognizable by WMA file, and then amplifying it back
> to normal. The arftifacts are kinda interesting there.

The artifacts are are result of the lossy encoding method used by WMA
files. No fruitful comparison can be made between the lossy encoding 
of WMA and low bit rate PCM.

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo  n...@mega-nerd.com (Yes it's valid)
+-----------------------------------------------------------+
A good debugger is no substitue for a good test suite.

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Erik de Castro Lopo <n...@mega-nerd.com> wrote in message news:<4...@mega-nerd.com>...
> Curious wrote:
> > 
> > Low-bitrate WMA files have a pleasant type of distortion to them.
> > Couldn't say the same about low-bitrate WAV files.
> > 
> > WMA "noise" tends to be musical while WAV "noise" tends to resemble
> > square-waves.
> 
> ??????????????
>  
> > I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to
> > where it is just recognizable by WMA file, and then amplifying it back
> > to normal. The arftifacts are kinda interesting there.
> 
> The artifacts are are result of the lossy encoding method used by WMA
> files. No fruitful comparison can be made between the lossy encoding 
> of WMA and low bit rate PCM.
> 
> Erik

Where -- on the internet -- can I find technical information on WMA
compression?

Most websites that discuss audio compression talk about MPEG, AC-97
and other types of compression. They get very little -- if at all --
into WMAs.

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Jerry Avins wrote:

> Curious wrote:
> 
>> The quantum of WAV file is a square wave...
> 
> Where did that strange idea come from? For file formats, check out
> http://www.wotsit.org/ and http://sox.sourceforge.net/AudioFormats.html.
> 
> What you don't know doesn't hurt much. The major trouble comes from the
> the falsehoods you believe.
> 
> Jerry

I think Radium may be back.

Jim A.

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WMA is part of Microsoft's .ASF family. The encoding/decoding algoritms are
concidered "secret" and are known to Microsoft employees only.

I bet you'll find more information about MPEG encoding. This information is
considered free for non-commercial use.

What do you want to achieve with WMA encoding, anyway? You better take a
look at AACplus. That rocks your socks of when it comes to compression on
lower bitrates.

Best regards,
Rob
"Curious" <c...@yahoo.com> wrote in message
news:3...@posting.google.com...
> Erik de Castro Lopo <n...@mega-nerd.com> wrote in message
news:<4...@mega-nerd.com>...
> > Curious wrote:
> > >
> > > Low-bitrate WMA files have a pleasant type of distortion to them.
> > > Couldn't say the same about low-bitrate WAV files.
> > >
> > > WMA "noise" tends to be musical while WAV "noise" tends to resemble
> > > square-waves.
> >
> > ??????????????
> >
> > > I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to
> > > where it is just recognizable by WMA file, and then amplifying it back
> > > to normal. The arftifacts are kinda interesting there.
> >
> > The artifacts are are result of the lossy encoding method used by WMA
> > files. No fruitful comparison can be made between the lossy encoding
> > of WMA and low bit rate PCM.
> >
> > Erik
>
> Where -- on the internet -- can I find technical information on WMA
> compression?
>
> Most websites that discuss audio compression talk about MPEG, AC-97
> and other types of compression. They get very little -- if at all --
> into WMAs.

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Erik de Castro Lopo <n...@mega-nerd.com> wrote in message news:<4...@mega-nerd.com>...
> Curious wrote:
> > 
> > The quantum of WAV file is a square wave. 
> 
> No, the quantum of a WAV files is the unit impulse.

What does the waveform of a "unit impulse" look like on a graph?

Is this the same as the "impulse wave" on the NCH tone generator
software?

For NCH info:

http://www.nch.com.au/tonegen/

> > What is the quantum of a WMA file?
> 
> WMA files decode to PCM audio which is what you have in standard
> WAV files.
> 
> Erik

What the WMA-equivalent of this "unit impulse" and what does it look
like on a graph?


What interests me is why "WMA noise" consist of pleasant tones while
"WAV noise" just plain boring noise. What in WMA is responsible for
the tones?

I have Adobe Audition 1.0. I generate a silent file. I save it as WMA
20 kbps, 44.1 KHz, mono. I convert file this to WAV and then back to
WMA several times. I make my last conversion to WMA and save it. I
then open this WMA file. Finally I increase the volume of the audio in
the WMA file and play. Intrigueing tones result. These tones are
typical in low bit-rate, high-sample rate WMA files.

If anyone has a valid email address I can send them a WMA file with
the characteristics I am talking about.

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Curious wrote:
> 
> Erik de Castro Lopo <n...@mega-nerd.com> wrote in message news:<4...@mega-nerd.com>...
> > Curious wrote:
> > >
> > > The quantum of WAV file is a square wave.
> >
> > No, the quantum of a WAV files is the unit impulse.
> 
> What does the waveform of a "unit impulse" look like on a graph?

ASCII art (ie only make sense with fixed width font):

                             .



      zero  ................. .....................

which each '.' is a time domain sample.

> Is this the same as the "impulse wave" on the NCH tone generator
> software?

Probably. "Unit impulse" is a standard DSP term.
 
> What the WMA-equivalent of this "unit impulse" and what does it look
> like on a graph?

No idea. Maybe you should generate an impuse, encode it as WMA and
then decode it back to WAV.

> What interests me is why "WMA noise" consist of pleasant tones while
> "WAV noise" just plain boring noise. What in WMA is responsible for
> the tones?

WMA is a "perceptual encoder". It analyses audio, figures out
where the tones are and which tones are most important to the
perceieved sound and then stores these while throwing away
the reset.

> I have Adobe Audition 1.0. I generate a silent file. I save it as WMA
> 20 kbps, 44.1 KHz, mono. I convert file this to WAV and then back to
> WMA several times. I make my last conversion to WMA and save it. I
> then open this WMA file. Finally I increase the volume of the audio in
> the WMA file and play. Intrigueing tones result. These tones are
> typical in low bit-rate, high-sample rate WMA files.

Considering how a perceptual encoder works, I do not find this
suprising. I would expect similar results with MP3 and Ogg Vorbis
codecs.

> If anyone has a valid email address I can send them a WMA file with
> the characteristics I am talking about.

My email address is valid, but please do not send me a file.

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo  n...@mega-nerd.com (Yes it's valid)
+-----------------------------------------------------------+
"When your hammer is C++, everything begins to look like a thumb."
-- Steve Haflich, in comp.lang.c++

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