Recorded CD's... Second edition.

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

212.27.58.141

More info :
I will state my experiment more clearly as I feel I was a bit on the fuzzy side in my last
message...
1. I extracted audio from an original audio CD (disk A).
2. I burnt this audio on a cheap CDRom at 4x (disk B)
3. I extracted this copy (disk B) and compared it to the wav-files extracted from disk A at
step 1.
It was perfectly identical. (byte-by-byte comparison of binary files, with a file comaprator
utility, no differences found. (*)See remark at the end of the message)
This does not mean anything about the exactitude of the FIRST audio extraction (step 1, the
one that generated the WAV-files). However I extracted disk A on both my CDROM-reader
and my CD-Burner and the files were identical (*)).
However this means for sure that audio data that was written on disk B, then read again,
(steps 2 and 3) did not change for a single bit. If we use telecoms terms, the channel
(burner+disk+reader) has a BER of 2e-10 or less (counting error correction codes).
Therefore there is no question to ask about "CD recorder BER" : This BER exists, but we
cannot determine it here because we cannot read the encoded data on the CD. We only have
access to the decoded data, i.e. the audio stream. But we can see the recorder BER is below
the error-correction code threshold as no error was detected. (even if ECC codes in audio
CDs are not very strong, they still work).
This was at 4x on a cheap CD and a cheap burner.
It is very likely that the pits burnt into the CD at 4x are less "clean" that at 1x. However my
CD-ROM reader was able to make a perfect read even if the CD was burned at 4x.
Therefore, if an audio CD reader makes errors while reading this 4x recorded CD, this means
that its performance is inferior to that of my cheap IDE CDROM reader.
This would not surprise me at all, because a CDRom reader is able to read at 48x maximum,
which means around 90 Mbits/s. Its synchronization system must be much more competent that
the one in a CD player, which reads at 1x, or around 2 Mbits/s. Also, EAC reads multiple
times.
Conclusion : it is not the media, nor the burner, the culprit is the player.
Thus, I'm gonna try to design a CD transport with an old PC motherboard and a CDROM
reader ! I'm thinking about building an amp right now, so I'll tackle this in some time. Anyone
interested in joining ?
--

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Topic - Recorded CD's... Second edition. - Peufeu 06:00:47 09/12/00 (1)

the burning question remains ... - Mart 06:49:51 09/12/00 (0)

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