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[lalittle]

Could someone please clarify the following statement from the Secure Rip log:

The quality percentage is the ratio of the minimum number of re-reads
to the actual number of re-reads of the CD data sectors.

As simple as this probably is for most people, I don't understand what it means.  I thought that re-reads were re-reads, so I don't understand the difference between "minimum" and "actual" re-reads.  Wouldn't the "minimum" number always be zero?

If the quality percentage is 100%, does this mean that ZERO re-reads were necessary, or can you have a re-read and still get a 100% quality report?

Also, can a drive's error correction interfere with the accuracy being reported in the Secure Rip Log?  In other words, can the CD drive's internal capabilities "hide" the fact that some re-reads were needed, resulting in the log saying "100%" even though some re-reads actually were needed?

Thanks for clarification on this,

Larry

[glynor]

I'm curious too.  I searched around on HydrogenAudio but didn't find many specifics...

[JohnT]

In secure rip mode it always does at least one re-read of each sector, so the minimum number of re-reads is one per sector.

The algorithm is: it reads a range of CD sectors, then reads the same sectors again. If the two reads result in identical data, it moves on to the next range of sectors. If the two reads are different, it re-reads the same sectors until it gets an identical match. If it doesn't get a match after 16 tries, it gives up.

The quality percentage is calculated like this:

Q = quality percentage
m = minimum number of sector re-reads (equals the number of sectors)
n = actual number of sector re-reads

Q = m / n * 100


Example:
A track has 1000 sectors, 900 sectors return good data on the first "re-read", 100 sectors require one additional "re-read" to return good data. So:
m = 1000
n = 1000 + 100 = 1100
Q = 1000 / 1100 * 100 = 91%

If there were sectors that never returned good data, the number of re-reads is artificially scaled up to make the quality percentage look a lot worse. So you see it's not mathematically precise, it's meant to give a subjective indication of the rip quality.

Since error reporting from CD drives is not very reliable, we don't use it. Therefore, the quality percentage only reflects the number of re-reads we do and does not include any information about what the drive itself may be doing underneath.

[NickM]

Notwithstanding the explanation, I still don't think that the number (subjective or not) is very useful!

What may be more useful would be first a message that the disk was ripped with no '16 re-tries', i.e. the rip is perfect.  And then an indicator as to the number of sectors that needed more than one re-read.
The output could be as follows:-

"Perfect secure rip, no re-tries"
"Perfect secure rip, 14% of sectors needed re-reading"
"Secure rip, 25% of sectors needed re-reading but 2% of sectors could not be verified"

[lalittle]

Thanks for the explanation and feedback on this.

Larry