On Thu, 2009-07-30 at 11:42 -0400, Tom Ryan wrote: > > On 7/30/09 7:38 AM, "Andy Walls" <[email protected]> wrote: > > Since, I've now implemented 1 custom control, adding more > should be > pretty easy. Give me a few days, and I should have something > for you to > play with.
Tom, OK. I've got about 14 or so new user controls in the cx18 driver at http://linuxtv.org/hg/~awalls/v4l-dvb They are: extra_12db_gain (bool) : default=0 value=0 Use this if you suspect a weak signal. Since these are locally connected cameras on 24 VAC with hopefully a short cable run for testing, I doubt you need this, luma_droop_compensation (bool) : default=0 value=0 chroma_droop_compensation (bool) : default=0 value=0 If you enable these, they will turn on impedance boosting for CVBS/Y and C/Pr/Pb respectively. You would use these, if you had a cable or a source that wasn't 75 ohms or some ohter reason for a bad impedance match. This setting can cause the signal to get a DC offset, on the boards, so if you use this, you should also use clamping (see below) luma_clamping (bool) : default=0 value=0 This will enable clamping of the CVBS/Y sync tip to a specific analog voltage level that should be below the midcode output level of the ADC. This will remove positive DC offset, but can also give very weak signals a negative DC offset in manual mode (see below). You should probably try this setting. You likely have to use this setting if droop compensation is enabled. chroma_clamping (bool) : default=0 value=0 This will enable claming of the C/Pr/Pb signal voltage to 0 V, the ADC midcode clamp level. This doesn't matter for your security camera. auto_luma_clamping_level (bool) : default=1 value=1 When luma_clamping is enabled and this setting is enabled, the CX23418 will attempt to automatically adjust the sync tip clamping level for you. You will want to leave this set at automatic when you first enable clamping, to see if the CX23418 can do the work for you. If not, turn it off, and set the clamp level manually (see below). luma_clamping_voltage (menu) : min=0 max=7 default=0 value=0 0: -1.05 V 1: -0.8 V 2: -0.606 V 3: -0.460 V 4: -0.348 V 5: -0.264 V 6: -0.2 V 7: 0 V This lets you manually set the luma sync tip clamping level to some voltage below the midcode point (0 V) of the ADC. You must turn luma clamping and turn off auto luma clamping level for this to be control to be effective. Setting the sync tip clamp to 0 V will for sure be useless. In my mind, the lower the voltage the better. auto_digital_gain_control (bool) : default=1 value=1 digital_gain_level (int) : min=0 max=4095 step=1 default=256 value=1092 flags=slider These control the digital front end gain that are applied digitally after the analog gain stages and the AGC. This gain level is a rather fine adjustment. There probably not much point on setting this to manual and fine tuning the digital front end gain, unless you've already done a manual setting of the analog front end gain first (see below). auto_analog_gain_control (bool) : default=1 value=1 analog_gain_level (int) : min=16 max=248 step=1 default=64 value=32 flags=slider This gain controls the analog stages before the ADC. You have to take it out of auto before your manual gain setting will take effect. The extra 12 dB gain stage comes before this one (in case you had it enabled for a very weak signal). sync_tip_height (int) : min=0 max=255 step=1 default=220 value=220 flags=slider This is the height of the sync tip the timing circuitry is expecting or the AGC circuitry is aiming to achieve (I'm not sure which, maybe both). I don't know what the unit are. auto_sync_height_crush (bool) : default=1 value=1 This control lets the digital front end adjust the sync_tip_height register downward, if a sync signal comes in that exceeds the range of the AGC. I;m not sure what the consequences are of turning it off. I've never seen mine adjust the sync_tip_height (not that I've looked alot). sync_acquired_error_threshold (int) : min=0 max=255 step=1 default=16 value=16 flags=slider sync_lost_error_threshold (int) : min=0 max=255 step=1 default=32 value=32 flags=slider These two are sync tracking lock declaration thresholds. If the measured sync signal is within the acquired error of the sync tip height, lock is declared. If the measrued sync signal is outside of the lost error tolerance, then the sync circuitry will delare sync was lost and begin a search algorithm. Note that the difference in values gives you some hysteresis. For meaningful operation, the acquire error threshold must be less than the lost error threshold. > > Thanks very much! I am trying to track down an oscilloscope (would a > video of the output suffice?) Yes, actaully a picture would do. I'd need to see the voltage levels relative to 0 V, the shape of hysnc tip, some of the active video, and I'd need the time scale too. I'll need to knwo how the measurement was taken: 1. clipped to the cable ground and probe tip on the cable center pin with no load 2. a 75 ohm resistor connected from cable center pin to ground, and the signal measured across the resistor 3. the camera connected to the HVR-1600 with a 75 ohm T connector located close the HVR-1600 end, with the measurement made from the center pin and ground of the open T. > and I would be willing to ship you one of the cameras if you’re > interested and these changes don’t work out. There are some more setting I have yet to program in as user controls. The chip is extremely flexible. So I wouldn't want a camera sent jjust yet. I also have very little time in the next month, so I'd prefer not to have someone's equipment until I know I have time. Regards, Andy > Let me know. > > Tom > > _______________________________________________ > ivtv-users mailing list > [email protected] > http://ivtvdriver.org/mailman/listinfo/ivtv-users _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
