Vorbis - Feb 2002 - compressed audio tutorial - "major" update

I've made a large update to the introduction to compressed audio.  I 
completely rewrote the first section, which I wasn't happy with.  It now 
features two diagrams (worth 1000 words each!), and is broken up into a 
couple of sections.

http://cs.leander.isd.tenet.edu/~mitchell/vorbis_intro.html

I have also continued to tweak other sections based on feedback from email 
and this forum.  All the feedback has been very helpful.

If you could all read at least the first two sections (the new ones).  Anyone 
wanting nitty gritty on the other changes can see the version history at the 
bottom.  Here is the list of what's been done since my last mention here:

        * modified end of "Just Say No to Bitrates" to clarify that
Vorbis doesn't
          target any specific bitrate when quality settings are used.  Includes
          large verbatim quote from an email by Carsten Haese
        * capitalized section headers throughout
        * added final paragraph to "Transcoding" section
        * colloquial improvements: removed "folks" and first-person
references
        * reworded a few sentences ending in prepositions
        * simplified sentence mentioning flac
        * put list of topics into introduction
        * changed "nearly 10 megabytes" to "approximately 10
megabytes"
        * wrong word in 2nd paragraph of "ABR/CBR/VBR"
("give" -> "gives")

By the way, the diagrams were my first try at making images in The GIMP, and 
I couldn't figure out how to ensure the PNGs had transparent backgrounds. 
If
they don't already, I'd appreciate some steps on how to do that.

By the way, the initial sine waves were generated using some very ugly Java 
and then screen captured, touched up and labelled.

http://cs.leander.isd.tenet.edu/~mitchell/SineWave.java


-- 
Graham Mitchell - computer science teacher, Leander High School
"REAL PROGRAMMERS don't write in BASIC.  Actually, no programmers
write in BASIC after reaching puberty."

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Quoting Graham Mitchell
<graham@grahammitchell.net>:
>
> I've made a large update to the introduction to compressed audio.  I 
> completely rewrote the first section, which I wasn't happy with.  It
now
> features two diagrams (worth 1000 words each!), and is broken up into a
> couple of sections.
I think the second diagram should not represent the samples as in a
bar chart, but as points (say 3 to 5 pixels in diameter). The reader
should still be able to see the sine wave they represent, and will
perhaps better understand that sampling in itself is "sort-of" a
lossy processus.

Kilobits per seconds is abbreviated "kbps", not "Kbps". Kilo
is always
lowercase k.


-- 
Adrien @ SJSU - adrien.beau@free.fr

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As everyone else has said, great doc.  The only thing that caught my eye as 
off was the thing about DVD audio being three times the size of CD audio.  I 
think the default sampling rate of DVD audio is 96 kHz, so it would do more 
than double the size of audio.

Just technical nit-picking.  :-)

-Scott

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"with each change in 10 dB corresponding to a doubling of the volume."

That's strange. My physics schoolbook tells me that each change in 3 dB 
corresponds to a doubling.

<p>Graham Mitchell wrote:
> I've made a large update to the introduction to compressed audio.  I 
> completely rewrote the first section, which I wasn't happy with.  It
now
> features two diagrams (worth 1000 words each!), and is broken up into a 
> couple of sections.
> 
> http://cs.leander.isd.tenet.edu/~mitchell/vorbis_intro.html
> 
> I have also continued to tweak other sections based on feedback from email 
> and this forum.  All the feedback has been very helpful.
> 
> If you could all read at least the first two sections (the new ones). 
Anyone
> wanting nitty gritty on the other changes can see the version history at
the
> bottom.  Here is the list of what's been done since my last mention
here:
> 
> 	* modified end of "Just Say No to Bitrates" to clarify that
Vorbis doesn't
> 	  target any specific bitrate when quality settings are used.  Includes
> 	  large verbatim quote from an email by Carsten Haese
> 	* capitalized section headers throughout
> 	* added final paragraph to "Transcoding" section
> 	* colloquial improvements: removed "folks" and first-person
references
> 	* reworded a few sentences ending in prepositions
> 	* simplified sentence mentioning flac
> 	* put list of topics into introduction
> 	* changed "nearly 10 megabytes" to "approximately 10
megabytes"
> 	* wrong word in 2nd paragraph of "ABR/CBR/VBR" ("give"
-> "gives")
> 
> By the way, the diagrams were my first try at making images in The GIMP,
and
> I couldn't figure out how to ensure the PNGs had transparent
backgrounds.  If
> they don't already, I'd appreciate some steps on how to do that.
> 
> By the way, the initial sine waves were generated using some very ugly Java
> and then screen captured, touched up and labelled.
> 
> http://cs.leander.isd.tenet.edu/~mitchell/SineWave.java
> 
> 
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> "with each change in 10 dB corresponding to a doubling of the
volume."
> 
> That's strange. My physics schoolbook tells me that each
change in 3 dB 
> corresponds to a doubling.
Isn't it +3 dB -> double power; +6 dB -> double volume?

Cheers,

 - Tomi

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