Browsing through the Wiki, I came upon the topic on gap setting in EAC. I decided to try some of my CDs and see what the gaps are like.

I was expecting to see 2-sec delays, but instead, the gap setting seemed more like random settings. 1.7, 1.5, 0.3, etc. hardly any of my pressed CDs have standard 2 second gap setting.

What's the reason for these strange gap settings? My best educated guess is that whatever program authored the CD in the first place, the gap is added so that the next track starts on a sector boundary? It seems unlikely that the audio engineer would add these kind of random gap settings... I tested some of the gaps for silence. some shows up as 100% silence, some shows up as .1% peak level... some strangely seem to have stuff in them.

And finally, I now know the complicated way to copy an audio CD through EAC. But surely there must be an easier way to make an identical copy of a CD and copy all settings including the precise gap setting right? Are there any program that does this? Does CloneCD do this?

Thanks!

There are many programs that can copy a cd with the subchannel info intact, but they dont do additional error detection to detect/correct errors from scratches. If you want to have a secure copy, then the only way to go is EAC or if you have a plextor - Plextools. -Martin.

Edit: The above is only for ripping...You can use any program for burning the rip to disc.

i dont know an awful lot about gaps, so i cant answer your q's on that, but as martin said, you can easily make an exact copy of a cd w/ eac. to maintain all of the gap in eac, you just need to have it create a cue sheet. this can be used w/ individual files for the songs, or with an image. imho, using the copy image and cue sheet function is the easiest way. this will result in your high quality, secure audio rip in a single file, and then your cue sheet as a seperate file w/ all of the gap info. you can then use eac, burrrn, or other apps to burn an exact copy of the cd, using those two files.

First of all, it's nothing to do with sector boundaries. A CD sector (aka block or frame) lasts just 1/75th second, so that would not explain it.

There is an art to timing the gaps between tracks when sequencing albums. Often, the gap will be timed so that it's an exact number of bars according to the rhythm of the preceding track. This makes the next track start at the "psychologically right time". For example, if a track is in 4/4 time and the pulse is 120bpm, then the producer might choose to put in a following gap that matches one bar of music, and in this case it happens to be 2 seconds. But if the track was a waltz in 3/4 time, at 100bpm, a one bar gap would be 1.8 seconds. There can of course be other artistic considerations in setting a suitable inter-track gap, but I don't profess to understand them - they are someone else's art, after all.

Then again, given the amount of care commonly applied to the production of modern CDs, the gaps could just as easily be random.

Interesting...
But usually the songs are so quiet at the end or have a fadeout that you don't hear it in any case...

So THAT's what subchannel is.

If the subchannel contains GAP information, then why does most CD copying software defaults to not copy those information for audio CD?

I would guess that it is because some old cd-rw drive cannot read/write those data. I've used CloneCD to copy audio/data CD, and I just checked, that option is disabled by default!



When I first encountered the term "subchannel" a few years ago, I thought it's additional audio track that may exist on the CD, and enable the option when a CD has no such track will put garbage (excess useless) data on the target CD, so I left it as unchecked.

Who the hell came up with those defaults?

For every 2352 bytes sector on a cd there is 98 bytes of subchannel data. Two of them are used for synchronization and the other 96 bytes forms the p-w subchannels. The p-q
subs holds timming information and the r-w subs can be used for cd-text and graphics etc. Also the toc of a disc is stored in the q subchannel in the lead-in. The gaps are stored in the q subchannel throughout the disc. Copy programs dosent need to copy the whole subchannel data for reproducing the gaps. They just scan the q subchannel throughout the disc and then saves the gap timmings in a cue sheet or a toc file, which then is used to reproduce the gaps on the copy. -Martin.

Just use the right software, no problem to do it...
No need to be angry, subchanel data are not that important to most people and so that goes for the default setup.
AFAIK all the drives can detect at least gaps if not all subchanel information...
I don't know but I can tell you that I don't see any problem there, everyone has the right to choose...

It is very hard to find any use for the gap information. That's why most programs don't care about copying it.
In fact 90 % of the times, gap info are used to be copied. People want to copy them, so they detect them.
10 % of the times, people use gap detection in order to remove silence from their ripped files (assuming that gaps are silent, which, as you saw, is not always the case).

If CD were suddenly produced without any gap information, no one woud notice, exept EAC users. These data are virtually unuseful.