Unstable AC3 Decoding

Canuck · Mar 5, 2003, 12:51 PM

I've had great success with the kx drivers but ever since I tried to use the AC3 5.1 mode to play DVDs (since kx3528) I have a problem where the audio starts out ok from all 6 speakers and then I start to hear some reverb and then all channels go into unstable oscillation causing loud buzzing.

I unloaded everything in the DSP except the FXbus and epilog and directly connected the 6 channels.

I put togther a one page website with an image of my DSP settings and some of the things I have tried. It also has a half meg wav file that demonstrates the problem.

The site is located at:

http://users.hfx.eastlink.ca/~cresth...3530__echo.htm

If anyone could have a look and listen and offer suggestions I would very much appreciate it.

Thanks,

Canuck

**Eugene Gavrilov** · Mar 7, 2003, 01:47 AM

AC-3 performance doesn't depend on kX DSP settings

at the moment AC-3 software decoding isn't 100% optimized and might produce average results. I suggest you use multichannel output instead (available on most DVD players)
also, you could try tweaking the number of buffers [kx icon -> settings -> setup buffers -> 8 buffers] - change it to a higher value

/Eugene

Canuck · Mar 7, 2003, 01:33 PM

Thanks for the reply Eugene. I gave that a try but it did not help.

When I tried to change the number of buffers I found the drop down lists were not working correctly. When you select the down arrow a small black shadow appears under the list box but the box does not open up. Clicking on the shadow did allow me to increase the number of buffers to 16 though.

Also there was no "Cancel" option on that panel, all you can do is press OK to exit. It would be nice to have a Cancel option to get out of there if you messed up the settings.

I may be looking in the wrong place for the source of the problem as I noticed that WinDVD cpu usage jumped by 50% as soon as the oscillations began. I'll try to find some other player and see if the problem persists with a different AC3 sound source.

Keep up the great work.

Mar 5, 2003, 12:51 PM	#1
Canuck DriverHeaven Newbie Join Date: Feb 2003 Posts: 18 Rep Power: 0	Unstable AC3 Decoding I've had great success with the kx drivers but ever since I tried to use the AC3 5.1 mode to play DVDs (since kx3528) I have a problem where the audio starts out ok from all 6 speakers and then I start to hear some reverb and then all channels go into unstable oscillation causing loud buzzing. I unloaded everything in the DSP except the FXbus and epilog and directly connected the 6 channels. I put togther a one page website with an image of my DSP settings and some of the things I have tried. It also has a half meg wav file that demonstrates the problem. The site is located at: http://users.hfx.eastlink.ca/~cresth...3530__echo.htm If anyone could have a look and listen and offer suggestions I would very much appreciate it. Thanks, Canuck

Mar 7, 2003, 01:33 PM	Thread Starter #3
Canuck DriverHeaven Newbie Join Date: Feb 2003 Posts: 18 Rep Power: 0	Unstable AC3 Decoding Thanks for the reply Eugene. I gave that a try but it did not help. When I tried to change the number of buffers I found the drop down lists were not working correctly. When you select the down arrow a small black shadow appears under the list box but the box does not open up. Clicking on the shadow did allow me to increase the number of buffers to 16 though. Also there was no "Cancel" option on that panel, all you can do is press OK to exit. It would be nice to have a Cancel option to get out of there if you messed up the settings. I may be looking in the wrong place for the source of the problem as I noticed that WinDVD cpu usage jumped by 50% as soon as the oscillations began. I'll try to find some other player and see if the problem persists with a different AC3 sound source. Keep up the great work.

Mar 7, 2003, 01:47 AM	#2
Eugene Gavrilov kX Project Lead Programmer and Coordinator Join Date: Dec 2002 Posts: 3,119 Rep Power: 75	AC-3 performance doesn't depend on kX DSP settings at the moment AC-3 software decoding isn't 100% optimized and might produce average results. I suggest you use multichannel output instead (available on most DVD players) also, you could try tweaking the number of buffers [kx icon -> settings -> setup buffers -> 8 buffers] - change it to a higher value /Eugene