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Re: Underruns on Audio CD Burns

Bill Davidsen <davidsen@tmr.com> wrote:

> I have an interesting problem burning one CD, I keep getting underruns. 
> I can avoid it by using a low speed burn, or live with it with the 
> burnfree option, but I don't understand why it occurs.
> The system is a P4-2.8G, 1GB memory, 40x CD burner. The O/S is FC1, 
> latest 2.4.22 kernel, and the burner runs in ide-scsi. The burn was done 
> as root, no warning messages, nothing else running. After the first bad 
> burn I checked that DMA and interrupts were enabled on the hard disk, 
> and set the fifo size to 50MB, larger than the longest track (22MB). 
> cdrecord is 2.01a31 and I tried the 2.01a19 which comes with FC1.

If this is true, then you need to contact the Linux Kernel peopel for a fix.

BTW: you are using outdated software.

	2.01a19 is 15 months old 

> What I don't understand is why/how there could be an underrun when the 
> fifo is larger than the track. It almost sounds as if the application 
> were not filling the fifo before starting the burn, but the minimum fill 
> was 95%, so that seems unlikely. I looked at the code quickly and saw no 
> obvious cause for this. I also watched the CPU usage which burning, and 
> it was always 60-70% idle. Since it ran at RR priority there should be 
> no issue with CPU performance.

It sounds like either the Kernel is not performant enough to send the 
SCSI commands fast enough or that an unfriendly "other" application is 
trying to break into the communication between cdrecord & the drive.


 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
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