[ivtv-users] cx18: horizontal sync issue with analog composite 1 input

[Andy Walls]

On Tue, 2009-07-28 at 14:30 -0400, Tom Ryan wrote:
> My answers are below..
> 
> 
> On 7/23/09 8:28 PM, "Andy Walls" <awalls at radix.net> wrote:
> 
>         On Thu, 2009-07-23 at 17:19 -0400, Tom Ryan wrote:
>         > Well, it worked good for a day and then started sync issues
>         again. We
>         > have narrowed the issue down to the particular device
>         connected to the
>         > analog composite input (a sony SSC-DC374 camera). If we
>         connect a vcr
>         > or a sony handycam to the cable, all is perfect. If we
>         connect a tv
>         > (instead of the card) to the cable, the output from the SSC
>         is
>         > perfect.
>         >
>         > The camera has an AGC (automatic gain correction) as well as
>         a level
>         > adjustment. We have tried adjusting them to various levels
>         and
>         > settings to no avail. (We have not worked the full gamut
>         though :)
>         >
>         > Any ideas, an option to the module load, etc that we're
>         missing???
>         
>         1. What card are you using?
>         2. What driver version are you using?
>         
>             Driver name   : cx18
>             Card type     : Hauppauge HVR-1600
>             Bus info      : PCI:0000:01:08.0
>             Driver version: 66048
>         
>         
>         3. How did you "up the gain on the cards" before?
>         
>         -c cx23418 -s 0x104 0x1

Hmm.  I think you meant "-c cx23418_843", otherwise nothing should have
happened.


>         4. What is the output of v4l2-ctl -d /dev/videoN --log-status
>         when you
>         don't have horizontal lock and when you do?
>         
>         no change
>         
>         5. Do you have an oscilliscope to look at the video signal
>         coming out
>         from the SSC-DC374 to compare it with a known working video
>         signal?
>         (It'll take the guessing out of troubleshooting)
>         
>         I do not. The patch didn’t help..

Hmmm. So much for adaptive gain adjustment via heuristics.

I have added a user control to the cx18 driver in a patch here:

http://linuxtv.org/hg/~awalls/v4l-dvb/
http://linuxtv.org/hg/~awalls/v4l-dvb/rev/2ef91a4f42a9

With the patched driver, turning on the extra +12dB of gain should be as
simple as this:

$ v4l2-ctl -i2
$ v4l2-ctl -L
$ v4l2-ctl -c extra_12db_gain=1

This control only boosts Luma (Y) and Chroma (C, Pb, Pr) signals and not
the tuner SIF audio.  It will re-adjust on input switches between Tuner,
CVBS, and SVideo to keep boosting (or not) the Luma and Chroma signals
for the new input configuration.

>         in case this helps
>         
> I found a user with the similar issue with another hauppauge card.
> 
> http://www.videohelp.com/forum/archive/hsync-issue-on-composite-capture-pvr500-t334215.html?layout=0&layoutalign=Center

I find it surprising a PVR-xxx board had this problem.

> ???????
> 
> Should I just get new cameras? Are there ones that people know will
> work??? :)

It may be cheaper to by a video signal amp/restorer for the camera.  (An
RF modulator from baseband up to channel 3 might work too.)  The camera
must have either a weak signal, large DC offset, or a really weird
output impeadence. 

Hopefully the patch will give you the signal quality needed for
horizontal locking, so no new hardware is necessary.

Regards,
Andy

> Thanks!
> 
> Tom