What is bit perfect?

[dhaen]

Jan,

I guessed what you were talking about, but couldn't resist the tease
Of course it's possible to error correct when copying, but sometimes it's better to copy the best "as is" data and error conceal far downstream.

[tschrama]

Just yesterday I edited a recording of a concert with GOLDWAVE, saved the .wav files, put it on audio CD with NERO. Then I ripped it again back to a .wav file with GOLDWAVE. Then I read extracted both the original and the CD-version with MATLAB, and compared them: perfect match, no bit errors.

So, a cheapy cd-rom recorder has allready bit-perfect performance?

[dhaen]

Or your reader gives the same read-errors each time!

[tschrama]

you mean,

maybe it has a write-error and the inverse read-error each time...?

[dhaen]

You read it twice, I believe...

[janneman]

Originally posted by dhaen
Jan,

I guessed what you were talking about, but couldn't resist the tease
Of course it's possible to error correct when copying, but sometimes it's better to copy the best "as is" data and error conceal far downstream.

Well, the Redbook Spec says it's not your business when to correct errors. A conforming drive does that continuously (because there are continuosly, thousands of bit errors on the disk) and transparantly. Whether you like it or not, the data comes off the disk essentially error-less. So there is no "as best" data; it's all the same, every read.

Jan Didden

[dhaen]

So there is no "as best" data; it's all the same, every read.

Jan,

This just can't be so. If a dust particle shadows a "pit" on one read, and not on the next, then the data is different.

Now we could argue about bit-correction. There will be correctable errors, and uncorrectable errors. It's also up to us when we error correct. I kow the Redbook is for player specification and standardisation, but the reading of raw data from (Red Book compliant) discs is surely beyond the scope of Redbook.

[fmak]

[QUOTE]Originally posted by Variac
[B]My computer drive slows waaaaay down when trying to extract a difficult CD ie .2x . It seems to me that there must be some correlation between speed and accuracy, that reading the data slowly is more accurate. I agree that reading the exact data over and over couldn't help, but my impression is that each reading comes out slightly differently- in which case rereading enough times to establish the most accurate read would be helpful.

--------------------------------------------------------------------------------This is what I have been trying to explain to the flat Earthers in Audio Asylum! Bit perfect is only the result of a statistical or averaging model
that is as valid or invalid as error correction or interpolation. It doesn't mean perefct audio streams as some seem to be saying.

What do people think?

Another fallacy seems to be the assumption in the same forum that packet audio transfer like usb is free of jitter, regardless of hardware, software and method of clocking.

[tschrama]

dhaen,

took a .wav file, burned it to cd-audio, ripped it to .wav, compare the .wav files: perfect match

write, read, compare...: perfect match....

[dhaen]

tschrama,

Ah, I see How big was the file? Where was it located on the disc........