> > Thanks for the info. > > What hard drives are you using ide or serial ata. Does it make a > > difference. Thanks > > There have been some references recently regarding disk drive types > relating to tdm400 noise problems. > > Has anyone established there is a correlation between drive hardware > and noise? > > If this is the case, it may be indicative of marginal interrupt timng > performance > on that hardware. > > FWIW the system described earlier has a single sata drive attached to > the Intel 925XCV mb on-board controller, from dmesg: > > atapci1: <Intel ICH6 SATA150 controller> > > The drive is a Seagate ST3250823: > > ad4: 238475MB <ST3250823AS/3.01>
One of the easiest ways to determine whether any disk drive is impacting audio quality is evaluate the system in a no-load environment. (eg, process a single call with nothing else going on in the system including no swapping.) Then compare the audio to the same test repeated while generating large amounts of disk activity. (If I recall, 'hdparm -t' generates lots of disk activity.) Tests conducted this weekend (but incomplete right now) suggest the OS is doing something that impacts the TDM card specifically. Not sure what that is as yet, but likely to have something to do with the pci bus and/or interrupt handling. Seems the TDM card implementation (at least in the RHv9 distro) is not being serviced in reasonable timeframes. I modified the zttest.c app to display the length of time required to receive 8192 bytes of data from the card. In all cases tested thus far, the 8192 bytes are received in about 1.021000 seconds (21000 microseconds to late). That would suggest the data arriving from a TDM card will miss a frame of data roughly every ten frames. That has a serious impact on trying to run things like spandsp, but less of an impact on pure audio. The tests on this single system indicate that playing with the pci latency values had zero impact on the TDM timing. Also, suggestions involving 'udma2' on the drive had zero impact. That only confirms that if there isn't any disk activity, those parameters would have no audio impact. To help identify the source of the delays, I built a new system this weekend from scratch. When that is complete, I'll use it to compare the differences in motherboards, OS distro's, and maybe kernel versions. Rich _______________________________________________ Asterisk-Users mailing list [email protected] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
