Hi Andy. > You can certainly use the v4l2-ctl that came with your distro.
Then that's what I'll do, it includes ivtv-tune, too. I was mostly concerned about possible incompatibility with the driver, maybe an ioctl not part of the v4l2 spec. > I don't think it's a board problem. I think it's an incoming signal > problem. If your cable signals on some channels are so strong that they > start overdriving the analog receiver front end (bumping into non-linear > regions of the amplifiers), then you can get intermodulation products > which will show up as noise on other channels. The 3rd order > intermodulation products can be particularly strong at frequencies > *higher* than the two or more strong channels that caused them. That's an interesting hypothesis. FWIW, about a year ago, the cable company upgraded our connection from outside. We're 200 feet from their box, and I think they replaced an RG-6 cable with RG-7, maybe RG-8 (not sure if I remember what the guy told me). That goes into the attic, where it's split to the cable modem and to an inline amplifier. It then goes into an 8 way splitter. From there it goes to various rooms, including mine. I'm pretty sure it's RG-6 cable going to a wall mount. Then a 50 foot RG-6 cable goes to a 4 way splitter to 3 foot RG-6 cables to the TV, PVR-150 in old computer, and the HVR-1600 NTSC & ATSC/QAM connectors. I first noticed the static when I had a extra split, 8 way to 2 way to a cheap 4 way. And mythtv was having trouble finding all my clear QAM channels. I was hoping eliminating the 2 way split and replacing the cheap 4 way with a better quality one would allow me to get all my QAM channels and possibly clear up the static. I would have thought there were lots of places where I was losing signal strength, but maybe not enough to make the HVR-1600 happy. Since my PVR-150 doesn't have a problem with static coming off the same splitter, I'm wondering if maybe the analog components on the HVR-1600 are inferior to the PVR-150. If so, do you have any opinion about what would be a better dual tuner card? Too bad they're not allowed to sell analog only cards anymore. > I think I have detected the symptoms you describe on broadcast channel > 32 (579.25 MHz) on my setup with my HVR-1600. The static is slight, but > it is noticable and consistent. I sure hope it's the same root cause. > There are relatively few strong over the air station where I am at. It > shouldn't take me too long to build up a spreadsheet of all the possible > intermodulation products that pairs of strong stations below channel 32 > could create on channel 32's frequency band. > > If I'm right, then attenuationing the strong stations with an external > attenuatior or filter should make the static go away. Would such a device be limited to a narrow frequency range? I guess I'm wondering if it would interfere with my ability to tune clear QAM channels. Although, since the HVR-1600 has separate inputs, I guess it doesn't matter. > Since I can reproduce this, I'll try and debug this without you going > through too many hoops. Hopefully the symptoms won't go away. Over the > air propagation can be weather and time of day dependent... Don't worry about me going through hoops. I see this as an opportunity to contribute. I wish OTA was an option for me. According to antennaweb, I would need a large directional antenna to get most of the stations I want. I would need three to get all the stations I want. I'm ENE of most Detroit area stations, WNW of two Canadian stations we like, and S of a Flint station we like. > This all looks OK, after a cursory glance. You may want to unload > lirc_i2c while testing, just to eliminate any possible unknown due to > lirc.. lirc_i2c is going to use the first I2C master of the CX23418 to > talk to the Z8 IR microcontroller chip. The analog tuner commands are > sent on the second I2C master of the CX23418 chip. Done. lirc_dev is still there, hope that's OK. > I was set to look for just NTSC-M. You were set to autodetect NTSC-M > NTSC-M as implemented in Japan, or NTSC-M as implemented in Korea. That > shouldn't have affected things, but you can try and set it back to just > looking for NTSC-M with v4l2-ctl, to see if it make a difference. Must be a myth thing. It gives you a choice between NTSC and NTSC-JP, no mention of Korea. I will try setting it to just NTSC-M. >> Anyway, I'm now going to hook up the DVD player and see what happens. > > For inputs other than the analog RF tuner, I suspect you won't get the > static. > > Also for an RF source with only one (e.g a VCR) or only a few weak (e.g. > rabbit ears and a UHF loop or bow) RF channels, I suspect your > HVR-1600's analog tuner won't produce the static. 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? > Meh, no big deal. Although if you can prevent the line wrap next > time.... I'll try to remember. > The driver will refuse to stuff custom VBI packets in a DVD stream, > since the driver doesn't know how to do this in software. That prevents > your stream from getting corrupted. Mind if I go off-topic and ask about the status of VBI? The ivtv driver adds a private data stream containing VBI data to a DVD stream. I assumed that eventually, the cx18 driver would do the same. If I change to MPEG-PS, will I get that VBI stream now? If you need a tester for this feature, I'm very interested! I did test the S-Video/Line-In inputs. No static. And channel 29 still has static, despite removing lirc_i2c. It's getting late and I'm feeling less pressure since it looks like you've got a plan. I will do more testing with your parameters over the weekend. TTYL, Helen _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
