On Sat, 2009-04-18 at 02:10 -0400, faginbagin wrote: > Hi Andy, > > First, I thought you might be interested in some testing I've done. I > configured my card to match yours, i.e. standard, bit rates, stream > type. And I still had static on channel 29. Then I ran through all the > cable channels and tried to quantify the levels of static I heard on > each station. It's subjective and I want to repeat it, and spend a > little more time on each channel, because sometimes the longer I stay > with a channel, there's a chance the static will clear up to some > degree. Anyway, here are my notes from my first pass: > > No sound on 18, 41 > Static not noticeable on 2, 3, 5, 16, 17, 20, 21, 54, 56, 59, 60, 61, > 62, 63, 64, 65, 66, 67, 68, 69, 70, 81, 82, 83, 84 > Not noticeable on 22 (although ivtv-tune did not report "Signal detected")
Channel 22 is at 169.25 MHz which is the last channel freq at the high end of the Low-VHF preselector filter in the tuner. It might be getting knocked down by this preselector filter a little, compared to other cable channels in the the Low-VHF range (2-6, 95-99, and 14-21). > Slight on 23, 25, 56, 57, 87 > Some on 4, 7, 8, 10, 11, 13, 14, 15, 24, 26, 27, 33, 34, 41, 43, 46, 47, > 49, 51, 52, 53, 55 > Annoying on 6, 29, 30, 31, 32, 36, 37, 38, 40, 42, 58 > Not noticeable to annoying on 19 changed with image and/or speaker > Really annoying to annoying on 12, 28 changed with image > No sound to really annoying to annoying on 35 > White noise & video on 39, 71-80, 85, 86, 88-116, 118-125, same on TV > (no signal detected by ivtv-tune) What do you mean here? Sound is "white noise" but the video is viewable? Is the video clear or very snowy? Also, a separate TV set is exhibiting the exact same symptoms? > I should get 39 (HSN), 85 (JWLTV), 95 (TBN), 107 (GEMSTV) but not the others > No sound to really annoying on 44 > No sound to annoying on 45 > Really annoying to annoying on 48 > Really annoying to some on 50 > No sound on 117 (test pattern) > > Hope they make sense. If it will help, I'll put them in a spreadsheet. > Maybe a subjective scale from 0-4? Here are my definitions: > > 0, Not noticeable: I can't hear static at normal volume > 1, Slight: I might not notice it if I weren't listening for it. > 2, Some: I notice it, but it's lower than the other sounds. > 3, Annoying: About the same volume as other sounds. > 4, Really annoying: louder than the other sounds. Just to confirm, most of your observations are with the HVR-1600 and not on the PVR-150 or another TV (except where noted)? > > An unterminated splitter output can cause reflections that show up as > > elevated noise floor. > > That is a possibility. I don't think we have TVs hooked up to all the > outputs from the 8 way splitter, although I'm 99% sure they all go to > one room or another. It's a good thing to do. It will improve signal to noise ratio. It likely won't fix your static problem, but if you had any ghosting (a faint shifted copy of the same channel on the video) it should help. > > You, however, may want to just try bypassing you in line amplifier and > > seeing if the static goes away. > > I can probably do this as a test, move the computer to the office and > use the cable modem's unamplified connection. If it works, I'll have to > go into the attic to effect a more permanent solution. Not something I > look forward to, it's got this fluffy insulation that gets all over the > place. OK. But you're also taking a number of slitters (and hance loss) out of the test as well. Each equal 2 way split is > 3dB of loss. Each equal 4 way split is > 6 dB of loss. Each equal 8 way split is > 9 dB of loss. Smaller in line amplifiers are ~ 10 dB of gain. The net effect of moving to that cable modem drop could be a gain of a few dB and not a loss. Just let me know how the static sounds. I have that fluffy (cellulose?) insulation as well. Good stuff, but you never want to open the attic - the stuff goes everywhere. > >> Hmm, I do have an old Gemini cable box. I think it's 20+ years old. > >> Would it be a useful data point if I hooked it up to the HVR-1600? > > > > Well. We know a cable box will only output on channel 3. There is no > > chance for intermodulation products and you will also only exercise the > > low VHF part of the analog tuner. Your problem on channel 29 manifests > > with the UHF part of the tuner with many channels available. If the > > static persists with the cable box attached, we'll know it's not a > > signal problem if one assumes the analog tuner is not defective. > > So it wouldn't be a waste of time, right? If the static persists with just a cable box that outputs on channel 3, the problem is likely a problem in setting up the front end digitzer in the CX23418 or a defective analog tuner on the HVR-1600. > I'll probably try this first, since it's easier than moving the computer > around. 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) # v4l2-dbg -c host0 -s 0x2c72014 0xb05 Register 0x02c72014 set to 0xb05 # v4l2-dbg -c host0 -g 0x2c72014 ioctl: VIDIOC_DBG_G_REGISTER Register 0x02c72014 = 305h (773d 00000011 00000101b) Listen for a difference... Then change it back: # v4l2-dbg -c host0 -s 0x2c72014 0xb25 Register 0x02c72014 set to 0xb25 # v4l2-dbg -c host0 -g 0x2c72014 ioctl: VIDIOC_DBG_G_REGISTER Register 0x02c72014 = 325h (805d 00000011 00100101b) These commands use the syntax of the newest v4l2-dbg utility. If you are using the older one, the command line args are slightly different. You must have root privleges to use v4l2-dbg. FYI, This sequence didn't make static go away for me on channel 32. Regards, Andy _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
