My pvr-500 audio goes bad about 50% of the time when I change channels (with mythtv or ivtv-tune). Like others, I have had some luck with correcting the problem by resetting the audio input with ivtvctl -q0 Unfortunately, this fix only works for me about 75% of the time.
I have been playing with cx25840 registers and looking for what is causing (or fixing) the problem. So far, it is not obvious to me. As far as how the "ivtvctl -q0" fixes it: I modified the set audio input call in the driver so that it doesn't actually modify any registers, but still does a soft reset (register 0x810 bit 0). It seems to be this soft reset that (sometimes) fixes the problem, not the changing of any registers. I tried a "diff" of the registers between when the audio was bad and when it was good. There was no consistent difference, but sometimes I saw 0x813 bit 3 was set (format detection loop complete interrupt asserted). I don't really know what that means. Also, sometimes I saw that register 0x804 could be either 0x01 or 0x11 for the same channel. I guess this just means sometimes there is SAP and sometimes not. I thought that maybe this is just a problem of the automated audio detection, so I have started to play with register 0x808 to manually set it. The documentation on this register is confusing me. I looks like the cx driver is initializing it to 0xf6. I modify this to set it to what I think my audio should be: BTSC, stereo. I set register 0x808 = 0x14 and that doesn't seem to work. Now when it goes bad, it is completely noise, rather than just strangly distorted as it was before. When it is working, it sounds great. I have to read through the cx25840 docs some more and see if I can understand the auto vs. manual audio settings. Also, if the auto audio detection is not working, this might just be because my cable signal is weak. When I first installed my pvr-500 a few weeks ago, the video signal was horrible and I ended up upgrading the 20 year old cable and splitters through my house. That fixed the video, but maybe the audio is even more sensitive. I might try a signal amplifier where the cable comes into the house. Jim --- Deyan Bektchiev <[EMAIL PROTECTED]> wrote: > Hans Verkuil wrote: > > On Monday 20 February 2006 20:37, Robert > Kulagowski wrote: > > > >>> Got the same problem here as a result of a > Gentoo update to 0.4.2. > >>> Like many, I'm using it with Mythtv so there may > be some issue with > >>> ioctl differences fro m0.4.0 to 0.4.2. I upped > to a 2.6.15 kernal > >>> at the same time. This is on a PAL pvr150. > >>> > >>> Sounds to me like a pre-amp being overdriven - > definite clipping > >>> 'fuzz box' (shades of the 60's) sort of sound. > >>> > >>> I've made another observation - if I change > channel to a tuner > >>> input and then back to the s-video (so I'm using > the external audio > >>> input again) then the audio is fixed. If I just > enter LiveTV on > >>> Mythtv (so it goes straight to the last channel > selected) then the > >>> audio is duff again!! > >>> > >> Do any of the devs have input on this? I'm going > to try 0.4.3 since > >> it's been release to confirm if this is still an > issue. > >> > I updated from 0.4.0 to 0.4.3 and have the issue now > on my PVR-500. > > > > I'm getting the impression that it is not too > difficult for someone to > > find the cause. Especially if switching input > fixes the problem. The > > datasheet of the cx25840 is available here: > > http://dl.ivtvdriver.org/datasheets/video/ > > > > Only a few registers are changed by switching > inputs, so it cannot be > > too difficult to find it. > > > > I personally have never noticed it, and I > unfortunately do not have the > > time to investigate either. > > > > So I'm hoping someone can step in and try to find > the cause. I'm willing > > to help with tips and advice and such. > > > > The easiest way to start would be to add debug > messages in the places > > where registers are set (cx25840_write and > cx25840_write4) and see > > which regs turn up when you switch inputs to fix > the tinny audio. Then > > check the datasheet to see what those registers > actually do. > What I found out though is that in myth, if I set > the recording volumes > to be ~80% the audio is OK. > > What I also noticed was that the volume on my > PVR-350 was quite a bit > lower than 0.4.0 and remember that people > were complaining of the reverse and a change being > done to fix this. > > So maybe that same change that brings up the volume > on the 150/500 for > some is the one that causes the tinny audio for > others. > > If I get some time, I'll try tracking this down but > my work schedule is > so crazy (Silicon Valley startup) that I can't > promise anything. > > Regards, > Dejan > > _______________________________________________ > ivtv-devel mailing list > [email protected] > http://ivtvdriver.org/mailman/listinfo/ivtv-devel > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ ivtv-devel mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-devel
