I've updated the "Introduction to compressed audio with Vorbis"
tutorial
based on the many good corrections and suggestions I got here.
Changes were:
fixed range of 16bit samples (-32768 to 32767 rather than 0 to 65535)
added sentence on why 44.1KHz was chosen for CDs
added Sony's name as developer of CD format
wrong word ("Which" -> "While")
reworked CBR/ABR/VBR section with corrected info
added section on "Why Vorbis?"
sound quality is high
patent-free and open source
nice features (tagging, peelable, more than two channels)
added paragraph on ABX
mentioned that lossless stereo coupling kicks in at -q 5
put "transcoding" in quotes since it's a misnomer
Please give it another read, especially those of you with keen eyes. I'd
like to get it finalized and up on vorbis.com soon.
http://cs.leander.isd.tenet.edu/~mitchell/vorbis_intro.html
--
Graham Mitchell - computer science teacher, Leander High School
"Come thou no more for ransom, gentle herald. They shall have none, I
swear, but these my joints, which if they have as I will leave 'em them,
shall yield them little." - Henry the Fifth
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On Friday 08 February 2002 03:14, Graham Mitchell wrote:> Please give it another read, especially those of you with keen eyes. I'd > like to get it finalized and up on vorbis.com soon.I hadn't read it before, but now I did. I have a few remarks: "Extensive listening tests showed that only a small percentage of sound engineers could tell which sound was the original "full-quality" one, and which one was the "CD-quality" one" Right. But this is about listeners, isn't it, not about engineers? Why should the opinion of engineers be more important than that of testers with the good ears? "Special-purpose compressors (like flac) do exist, which were designed solely for losslessly compressing audio (...)" I don't really like this construction with do exist and which. But I don't really have a better solution for it. "There do exist special-purpose compressors (like flac), which were designed (...)" isn't any better. Maybe "Special-purpose compressors (like flac) which were designed solely for losslessly compressing audio do exist, but even they (...)". English isn't my native language though, so feel free to ignore this one. Thirdly, it took me a little while to realise why the number 1,411,200 was associated with CD's, while before it was 176,400. Perhaps you could change that sentence in "A bit on bitrates" to "Actual, uncompressed, CD-quality uses 1,411,200 bits (176,400 * 8) bits to store each second". I also agree that the first four paragraphs can be done better. Other than these minor things I think it's a well-written piece that does a good job of explaining to people how audio compression works, that mp3 is outdated, why using ABR is not as good as VBR, and how to use the quality settings of Vorbis to get good quality .oggs. Well done! Lourens -- GPG public key: http://home.student.utwente.nl/l.e.veen/lourens.key --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Graham Mitchell wrote:> I've updated the "Introduction to compressed audio with Vorbis" tutorial > based on the many good corrections and suggestions I got here.<...>> Please give it another read, especially those of you with keen eyes. I'd > like to get it finalized and up on vorbis.com soon.I'm a little concerned about the section about what quality to use: what if the user happens to choose an easy to encode track? In theory that shouldn't make any difference I guess, but there are types of sound that are difficult for lossy formats and that could need a higher quality settings to get good enough. Wouldn't it be better to recommend using some known problem samples (like applaud, castanets etc.)? -- Magnus Holmgren <p>--- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Magnus Holmgren wrote:> I'm a little concerned about the section about what quality to use: what > if the user happens to choose an easy to encode track? In theory that > shouldn't make any difference I guess, but there are types of sound that > are difficult for lossy formats and that could need a higher quality > settings to get good enough. Wouldn't it be better to recommend using > some known problem samples (like applaud, castanets etc.)?The point in quality settings is that you don't have to care about this. You get constant quality instead of having to figure out what bitrate to use for each track. If you chose a quality level where a complex clip becomes (very) annoying to you, you chose a wrong/too low -q value for your own ears. One has to be forgiving at q2 or q3 - some short, rarely happening and super-complex clips might sounds pretty different from the original even for untrained ears. This happens very seldom, though, and as long as it's not *annoying*, there's nothing wrong with it. <p>Moritz -- _______________________________________________________________________ "They who would give up an essential liberty for temporary security, deserve neither liberty or security" - Benjamin Franklin --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.