On Tue, 2009-04-21 at 03:00 -0400, faginbagin wrote:
> Hi Andy,
>
> I tried to do the following test.
>
> > As another test, you may also want to try this with v4l2-dbg with a
> > staticy sounding station tuned. It will switch the CX23418 to use the
> > mono audio out directly from the analog tuner through the CS5345 audio
> > chip, much like the audio line-in for Svideo or compsitie video-in. If
> > the static goes away, I'll know it's a CX23418 digitizer front-end
> > problem:
> >
> > # v4l2-dbg -c host0 -g 0x2c72014
> > ioctl: VIDIOC_DBG_G_REGISTER
> > Register 0x02c72014 = 325h (805d 00000011 00100101b)
>
> But the above get register command failed with:
> ioctl: VIDIOC_DBG_G_REGISTER
> ioctl: VIDIOC_DBG_G_REGISTER failed for 0x2c72014
>
> And dmesg didn't show anything.
>
> > # v4l2-dbg -c host0 -s 0x2c72014 0xb05
> > Register 0x02c72014 set to 0xb05
>
> And even though I couldn't get the current register value, I still tried
> the set. It also failed with:
> Failed to set register 0x02c72014 value 0xb05
That can happen when the cx18 and/or videodev module is compiled without
the CONFIG_VIDEO_ADV_DEBUG, or if the default /dev/video device does not
point to a cx18 supported device. It can also happen if you are not
root; changing registers is a privileged operation.
You may want to specify the device with the '-d /dev/videoN' switch.
Here's how you would scan to get some positive feedback that you can at
least query the driver:
# v4l2-dbg -d /dev/video0 -D
Driver info:
Driver name : cx18
Card type : Hauppauge HVR-1600
Bus info : PCI:0000:03:03.0
Driver version: 65792
Capabilities : 0x01030051
Video Capture
VBI Capture
Sliced VBI Capture
Tuner
Audio
Read/Write
# v4l2-dbg -d /dev/video0 -S
host0: cx23418 revision 0x01010000
host1: cx23418_843 revision 0x00008430
i2c 0x4c: cs5345 revision 0x00000000
(That's an HVR-1600 non-MCE)
> I was root, and I was using the newest utility I compiled. Also tried the
> one installed with the ivtv-utils package and got a usage message. So I
> assume I haven't changed the tuner to use mono audio out.
Correct.
> I did try
> playing a couple of "really annoying" channels. Two out of three were
> still really annoying (27 & 41), one (34) had improved to "slight".
> FWIW, here's the output from v4l2-ctl --log-status while 41 was tuned in
> and mplayer was going:
Well the v4l2-dgb commands had no effect. So I cannot say what caused
the change in quality.
> Any thoughts on why v4l2-dbg can't get/set that register?
See above.
> FYI, I scanned all the channels on my old computer with the PVR-150.
> No problems with static. However, when I got to channel 60, the video lost
> color, although the audio was still clean. After rebooting, I continued
> scanning. This time, I lost sound on channel 87, which follows some
> channels that have white noise (both audio & video, and on any TV). I
> tried unloading and reloading ivtv, which didn't restore the audio.
> Rebooting did the trick. All but one of the remaining channels have white
> noise, but when I did get to that one last channel, a test pattern with no
> sound, there was no static.
I've been investigating with my PVR-150MCE, HVR-1600MCE, and HVR-1600.
1. With the MCE devices where the analog tuners (LG TAPE H001F MK3 in
the PVR-150 MCE, and TCL MFMN05 in the HVR-1600MCE) have a TDA9887
demodulator chip, the static on channel 32 is more noticeable than on
the HVR-1600 with a TCL M2523_5N_E tuner that has a TDA9801 demodulator.
2. Using how noisy the Raw VBI CC lines show up in osc as a qualitative
visual measure of AM Signal to Noise ratio (SNR), Stations with a really
high AM SNR have good sound, as do stations with a really low/poor AM
SNR. The AM SNR on channel 32 seems to be bad, but not terrible
(somewhere in the middle).
3. Experiments with home-made in-line attenuators of 17.5 dB and 23.5 dB
did not improve the sound on channel 32. It only made the video signal
worse.
4. The tuner AF out (vs the SIF out that's normally used) still exhibits
static for the HVR-1600MCE and HVR1600
The only conclusions I can draw are
a. From 1 & 4: my static is likely originating via processes in my
antenna amplifier and/or the analog tuner assembly and not the CX23418
chip's front end.
b. From 3: The source of my static is *not* from intermodulation
products in the analog tuner due to signals that are too strong.
Some speculations I can make are:
c. From 2: The noise on Raw VBI lines, as is viewable with osc, *may* be
an indicator of static appearing in the sound.
d. From 2: The AGC take-over point being set in the demodulator stage of
the analog tuner - where the demod stage takes over gain control from
the 1st mixer/amp - may have something with why very noisy video signals
don't experience audio static, but why mildly noisy signal do experience
audio static.
I need to look into how the analog tuner is being configured and
experiment with some settings. Life has been very busy lately. It may
take me a while to find what's going on.
I also need to look at your other email, and ask some questions about
the cable box behavior.
Regards,
Andy
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