> And either someone is fucking the system up from his part or the same
> serial can be used for multiple CD's. Sometimes CDDB and FreeDB give you
> multiple choices, of which usually one or two is that actual album.

They don't work from the serial number as such, but they make up some sort 
of hash code based on the track lengths etc.

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>> What does it do if you play something that isn't in the database? 
>> (I.e., you pick up an instrument and play something yourself.)
> 
> I tried whistling a song to it once, I just got a text back saying it 
> couldn't recognise the song :-( grrrrr

I forsee this degenerating into something akin to the intros round from 
Nevermind the Buzzcocks. ;-)

>> AFAIK, the manufacturers didn't hand this data 
>> over, some poor sod collected it.
> 
> Or rather, multiple poor sods collected it :-)

Heh. Sounds almost like the way Linux happened... ;-)

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scott wrote:

> They don't work from the serial number as such, but they make up some 
> sort of hash code based on the track lengths etc.

I don't know about that... One time, I had a CD sitting on my desk, and 
I noticed that round the spindle hole there is some *tiny* writing 
that's barely readable.

I typed the code number into Google. It instantly gave me the entire 
track listing for the CD. (!) Just from the 200-digit code printed on 
the CD's surface. I imagine CDDB reads this same code. (It's almost 
certainly burned onto the data track as well as being printed on the label.)

The best thing is, the CD in question was "Best Trance Anthems EVER 
volume #1,374" or something! :-D

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> I don't know about that...

It works so that copies of audio CDs still give the correct result, actually 
reading up about it, any CD that has exactly the same number of tracks 
starting at the same points on the CD with the same total play time will 
give the same freedb/CDDB result.

> One time, I had a CD sitting on my desk, and I noticed that round the 
> spindle hole there is some *tiny* writing that's barely readable.
>
> I typed the code number into Google. It instantly gave me the entire track 
> listing for the CD. (!) Just from the 200-digit code printed on the CD's 
> surface.

Well yeh, I think that's more like a barcode, you know the one that most 
shops have a database for to convert bar codes to prices at the checkout.  I 
imagine at least some websites have CDs listed with their corresponding 
serial numbers.

> The best thing is, the CD in question was "Best Trance Anthems EVER volume 
> #1,374" or something! :-D

Yeh it's always cool when you're thinking "I bet nobody in the entire world 
could possibly have ever even played this CD, let alone typed in all the 
track names", and then wham you get the results back!

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>> I typed the code number into Google. It instantly gave me the entire 
>> track listing for the CD. (!) Just from the 200-digit code printed on 
>> the CD's surface.
> 
> Well yeh, I think that's more like a barcode, you know the one that most 
> shops have a database for to convert bar codes to prices at the 
> checkout.  I imagine at least some websites have CDs listed with their 
> corresponding serial numbers.

I always assumed that was how CDDB works, and why if you burn an 
identical copy of the original CD it totally fails to identify it.

> Yeh it's always cool when you're thinking "I bet nobody in the entire 
> world could possibly have ever even played this CD, let alone typed in 
> all the track names", and then wham you get the results back!

Somewhere I found a website full of barcodes. Just about anything, type 
in a barcode and it knows what it is! (Well, almost... If you read into 
this area, you quickly discover that actually there are several 
different barcode systems, most of them incompatible.)

Tangentally: One of the example projects in Real World Haskell is a 
barcode recognition system. As in, you give it a blurry picture of a 
barcode taken with your mobile phone, and it tells you the digits. Just 
by looking at the vertical bars. It even uses the check digit to make 
sure it's read it correctly.

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You think that's bad, before I deleted it I'd ripped a Shania Twain album of 
my ex-landlord's and it played immediately following Vivaldi's Four Seasons 
when I ran my music straight-through.

Slightly jarring, to say the least.

-- 
Tim Cook
http://empyrean.freesitespace.net

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scott wrote:
> Actually I have a phone book entry on my phone, which you can call, hold 
> your phone up to some random speaker (be it in your car, on the TV, etc) 
> for 10 seconds, then a few seconds later it texts you back the artist 
> and song name.  It's pretty neat and has worked every time I've tried it.

I just finished software doing that, except it would also recognise what 
radio station you're listening to, whether it was an advertisement and from 
whom, or whether it was a talk show and who was talking.

It would also do TV, and give you (for example) links to the MTV episode 
information, or the buy-this link if you listened to the Home Shopping Network.

(I'm hoping the bosses find some more money, but it's looking grim still.)

The audio identification is all based around taking a short sample and 
finding it amongst a set of larger samples. It's pretty freaky, because the 
algorithm even finds (for example) people covering songs.  We had an 
American Idol caller come in and the system said "I don't know who is 
singing this, but it's Yesterday by the Beatles." :-) Pretty cool.

So the Fraunhoffer stuff is recognising music based on frequency analysis, 
beat detection, and a couple other parameters that are of course secret. The 
signatures it generates are about 300 bytes/second of audio, with even less 
than that needing to actually be in memory at any given time for a 
preliminary match. But given that it's a linear size increase, I'm guessing 
it's something not unlike string matching, except with fuzzy audio 
characteristics. It's usually either a very good match, or one of these 
"Could be Celine Dijon, could be Mozart, could be Ozzy Osborne" kind of things.

> Maybe it works in the frequency domain, so takes the fourier transform 
> of the sample, then uses some fuzzy matching algorithm to see what it 
> matches up with?

Basically that sort of thing, yes.

>> (But then, so should identifying a CD by it's serial number, and 
>> apparently that is a "solved problem".)
> 
> What do you mean? Isn't the whole idea of a *serial* number that you can 
> identify which one it is?

CDDB works by looking at track lengths and positions. I.e., the information 
in the table of contents that says what sector each song starts and stops 
on. Audio CDs for some reason don't have serial numbers, UPC codes, lyrics, 
or cover art encoded on them, which seems like rather a loss to me. (Even 
stranger to me is that MP3 doesn't define that sort of thing either.)

-- 
   Darren New, San Diego CA, USA (PST)
   The NFL should go international. I'd pay to
   see the Detroit Lions vs the Roman Catholics.

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scott wrote:
> Yeh it's always cool when you're thinking "I bet nobody in the entire 
> world could possibly have ever even played this CD, let alone typed in 
> all the track names", and then wham you get the results back!

That was very handy with my wife's collection of chinese opera music, as I 
wouldn't have had any idea how to even transcribe the track names from the 
box to the computer. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   The NFL should go international. I'd pay to
   see the Detroit Lions vs the Roman Catholics.

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Invisible wrote:
> I always assumed that was how CDDB works, and why if you burn an 
> identical copy of the original CD it totally fails to identify it.

It always worked for me, even when I took MP3s I'd ripped before and burned 
them onto a new CD with cd-text included. As long as the tracks are the same 
length, it should work.

-- 
   Darren New, San Diego CA, USA (PST)
   The NFL should go international. I'd pay to
   see the Detroit Lions vs the Roman Catholics.

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Darren New wrote:
> Invisible wrote:
>> I always assumed that was how CDDB works, and why if you burn an 
>> identical copy of the original CD it totally fails to identify it.
> 
> It always worked for me, even when I took MP3s I'd ripped before and 
> burned them onto a new CD with cd-text included. As long as the tracks 
> are the same length, it should work.

Are you sure it's not just reading the track titles from the CD-text? :-P

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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