I have first noticed this when I was copying an audio CD. I took me something like half an hour to do it. So I decided to go a little bit further and investigate this problem. I discovered that this bug was occuring as soon as you want to burn audio tracks, no matter the way (Burning an NRG image, mastering an audio CD, copying an audio CD).
The problem is the following: With data tracks, nothing special occurs. Everything is fine. For example, with an ISO compilation of 496 MB, I get the following burn times on an LG-GSA4163B (What I call real burn time is the total time without lead-in and lead-out phase times):
[li]At 10x: Total time: 6:06 (Real burn time: 5:31)
[/li][li]At 16x: Total time: 3:53 (Real burn time: 3:28)
[/li][li]At 24x: Total time: 2:54 (Real burn time: 2:31)
With an audio CD compilation made out of WAV files, with a total size of 486 MB (something similar), same burner, same media, I get the following burn times:
[li]At 10x: Total time: 5:58 (Real burn time: 5:23)
[/li][li]At 16x: Total time: 5:55 (Real burn time: 5:29)
[/li][li]At 24x: Total time: 10:58 (Real burn time: 10:32)
Now you can see where the problem is: Burning at 24x an audio CD takes double of time of burning the same CD at 10x (BtW, the 10x bench seems to be OK, regarding 1500 KB/s rate). I tested this with different burners and different medias, and the same problem occurs.
This bug is not related to NeroLINUX, as with USB external devices, everything works without any kind of problem. It is related to some kernel problem.
I tried several kernel versions. This bug seems to be unreproducable with kernels <= 2.6.4 (Tested with SuSE 9.1). Note that this bug also affects cdrecord and other Open Source projects related to CD burning.