On Fri, 2008-11-21 at 15:28 +0200, Dmitry Podyachev wrote: > is any tools for it ? or is it possible to use some API from v4l for it > (I do not see any way - may be via some gpio ?)? > > 1. The strategy may be to check the AGC level after the AGC settles > > after tuning to a channel or switching to a baseband input. If the > > level is up near the top of the AGC's range, maybe +9 dB out of the +12 > > dB max (0x36 or 0x37 in register 0x488) then turn on the +12 dB > > amplifier for the input to get more dynamic range out of the final stage > > of the amplifier. > > > > > 2. Maybe you could also, after changing the channel and letting the AGC > > settle, record the AGC value for that channel or input and then put the > > AGC in a manual mode > > yes, but how? how write something manual to AGC register ? write c-code > or other way exist ? >
Look at the definitions on page 5-92 and 5-93 of http://dl.ivtvdriver.org/datasheets/video/cx25840.pdf And the experiment using v4l2-dbg as root: # v4l2-dbg -d /dev/video0 -R type=host,min=0x2c40488,max=0x2c4048f ioctl: VIDIOC_DBG_G_REGISTER 00 04 08 0C 10 14 18 1C 02c40480: f825ea1c 001020dc Note when using the HVR-1600's built in NTSC tuner, tuned to an over the air broadcast signal, VGA gain on my card is at 0x1c right now which corresponds to 0.875 or -1.16 dB: close to the middle of it's range. The Digital AGC, which comes after the VGA, has adjusted it's fine gain to 0x5ea. What gain is your card's VGA set at when video comes from the source with which you have problems? Regards, Andy _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
