I'm having a single-channel reception problem, and am hoping someone might have some suggestions on how I could resolve it. Paging Craig the cable guy, you out there?

I have a dual tuner system with a pvr-250 and a 350, and am using the 350's tv-out. All channels come in fine except channel 9, which just happens to be NBC. I can't live without scrubs, so I'd like to get this resolved. If I can do that, i can cancel my tivo service and move over to mythtv permanently!

Channel 9 is getting some "rainbow" colored interference that spans the range from annoying to uwatchable. Here's a pic of the problem. It happens all over the screen, although my photo only captured part of it in that instant.



here's what I know already:
- signal strength from the cable line in to my apartment is very strong
- Tivo and my TV do not exhibit the problem
- both tuners (250 and 350) exhibit the problem
- both tuners are the same type (type 2)

here's what I've tried already, with no luck:
- replace all splitters, cables
- run direct line from primary cable drop to a single pvr tuner input
- upgrade mythtv
- upgrade ivtv driver
- fine-tune reception from setup
- run extra ground lines from mythbox to various places
- isolate mythbox chassis ground (i know i know, its dangerous)
- searched ivtv-dev forum (no luck)
- searched mythtv users/dev forums (no luck)

here are my system specs:
Athlon XP 2200+
Soyo K7VME Motherboard (KM400 chipset)
512 megs RAM
200 Gb Seagate baracude IV 7200 RPM HD
PVR-250, PVR-350
250-watt microATX seasonic power supply
Fresh install of R5A22 using stock drivers

A problem like this was covered in a previous post, but the user claimed the reception issue just went away, so that wasn't too much help. I've also tried searching ivtv and mythtv dev/user forums with no luck.

Anyone have any ideas? I can usually figure these things out, but I'm stumped on this one... thanks.

How many times do you intend to post this?

_________________
cesman

When the source is open, the possibilities are endless!

ok, i finally decided to get off my duff and try to figure this thing out once and for all. after some more troubleshooting tonight, here's what i know:

I tried all of these, with no change in reception of channel 9
- removed PVR-250 from the system and tried using only pvr-350 w/ tv-out
- disabled pvr-350 hw mpeg decode, but still use pvr-350's tv-out
- brought a monitor over to my mythbox and tried disabling pvr-350's tv-out altogether (sw decode)

additionally, i plugged the pvr-250 into my windows box and loaded the windows drivers for it, switched to channel 9 and viola, channel 9 comes in crisp and clear.

so, i can only come to the conclusion that it must have something to do w/ the ivtv driver. perhaps i'm using the wrong tuner type? tveeprom reports tuner type 2 on boot (see below), but maybe that's wrong??


pertinent dmesg output (w/ both tuner cards present):
ivtv: ==================== START INIT IVTV ====================
ivtv: version 0.4.0 (tagged release) loading
ivtv: Linux version: 2.6.13.2-chw-3 SMP preempt 586 gcc-3.3
ivtv: In case of problems please include the debug info
ivtv: between the START INIT IVTV and END INIT IVTV lines when
ivtv: mailing the ivtv-devel mailinglist.
ivtv0: Autodetected WinTV PVR 350 card (iTVC15 based)
ACPI: PCI Interrupt 0000:00:08.0[A] -> GSI 16 (level, low) -> IRQ 18
ivtv0: Unreasonably low latency timer, setting to 64 (was 32)
tuner (ivtv): chip found at addr 0xc2 i2c-bus ivtv i2c driver #0
ivtv0: i2c attach to card #0 ok [client=(tuner unset), addr=61]
msp34xx: ivtv version
msp34xx: init: chip=MSP3448W-A2, has NICAM support, simpler (G) no-thread mode
msp34xx: $Id$ compiled on: Oct 9 2005 22:52:16
ivtv0: i2c attach to card #0 ok [client=MSP3448W-A2, addr=40]
saa7115 0-0021: saa7115 found @ 0x42 (ivtv i2c driver #0)
ivtv0: i2c attach to card #0 ok [client=saa7115, addr=21]
tveeprom: ivtv version
tveeprom: Hauppauge: model = 48132, rev = J323, serial# = 7112712
tveeprom: tuner = Philips FM1236 (idx = 23, type = 2)
tveeprom: tuner fmt = NTSC(M) (eeprom = 0x08, v4l2 = 0x00001000)
tveeprom: audio processor = MSP4448 (type = 1b)
tveeprom: decoder processor = SAA7115 (type = 13)
ivtv0: i2c attach to card #0 ok [client=tveeprom, addr=50]
saa7127 0-0044: saa7127 found @ 0x88 (ivtv i2c driver #0)
ivtv0: i2c attach to card #0 ok [client=saa7127, addr=44]
ivtv0: loading /lib/modules/ivtv-fw-enc.bin
ivtv0: loading /lib/modules/ivtv-fw-dec.bin
ivtv0: Encoder revision: 0x02040011
ivtv0: Decoder revision: 0x02020023
ivtv0: Allocate DMA encoder MPEG stream: 128 x 32768 buffers (4096KB total)
ivtv0: Allocate DMA encoder YUV stream: 194 x 10800 buffers (2048KB total)
ivtv0: Allocate DMA encoder VBI stream: 120 x 17472 buffers (2048KB total)
ivtv0: Allocate DMA encoder PCM audio stream: 455 x 4608 buffers (2048KB total)
ivtv0: Create encoder radio stream
ivtv0: Allocate DMA decoder MPEG stream: 16 x 65536 buffers (1024KB total)
ivtv0: Allocate DMA decoder VBI stream: 512 x 2048 buffers (1024KB total)
ivtv0: Create decoder VOUT stream
ivtv0: Allocate DMA decoder YUV stream: 24 x 43200 buffers (1024KB total)
ivtv0: loading /lib/modules/ivtv_init_mpeg.bin
tuner: type set to 2 (Philips NTSC (FI1236,FM1236 and compatibles)) by ivtv i2c driver #0
ivtv0: Initialized WinTV PVR 350, card #0
ivtv: ====================== NEXT CARD ======================
ivtv1: Autodetected WinTV PVR 250 card (iTVC16 based)
ACPI: PCI Interrupt 0000:00:09.0[A] -> GSI 17 (level, low) -> IRQ 19
ivtv1: Unreasonably low latency timer, setting to 64 (was 32)
tuner (ivtv): chip found at addr 0xc2 i2c-bus ivtv i2c driver #1
ivtv1: i2c attach to card #1 ok [client=(tuner unset), addr=61]
msp34xx: ivtv version
msp34xx: init: chip=MSP3435G-B6, has NICAM support, simpler (G) no-thread mode
msp34xx: $Id$ compiled on: Oct 9 2005 22:52:16
ivtv1: i2c attach to card #1 ok [client=MSP3435G-B6, addr=40]
saa7115 1-0021: saa7115 found @ 0x42 (ivtv i2c driver #1)
ivtv1: i2c attach to card #1 ok [client=saa7115, addr=21]
tveeprom: ivtv version
tveeprom: Hauppauge: model = 32031, rev = B110, serial# = 6151093
tveeprom: tuner = Philips FI1236 MK2 (idx = 10, type = 2)
tveeprom: tuner fmt = NTSC(M) (eeprom = 0x08, v4l2 = 0x00001000)
tveeprom: audio processor = MSP3435 (type = a)
tveeprom: decoder processor = SAA7115 (type = 13)
ivtv1: i2c attach to card #1 ok [client=tveeprom, addr=50]
ivtv1: loading /lib/modules/ivtv-fw-enc.bin
ivtv1: Encoder revision: 0x02040011
ivtv1: Allocate DMA encoder MPEG stream: 128 x 32768 buffers (4096KB total)
ivtv1: Allocate DMA encoder YUV stream: 194 x 10800 buffers (2048KB total)
ivtv1: Allocate DMA encoder VBI stream: 120 x 17472 buffers (2048KB total)
ivtv1: Allocate DMA encoder PCM audio stream: 455 x 4608 buffers (2048KB total)
tuner: type set to 2 (Philips NTSC (FI1236,FM1236 and compatibles)) by ivtv i2c driver #1
ivtv1: Initialized WinTV PVR 250, card #1
ivtv: ==================== END INIT IVTV ====================

finally got to the bottom of this one. Turns out it was a case fan causing interference! when i unplugged the fan, interference gone... ch. 9 now comes in loud and clear.

For the curious: the case i'm using has a temp-dependent fan controller, and it probably uses PWM to throttle the fan speed down, which is an excellent source of high-frequency noise. i wonder how much cleaner i could get reception by disabling the fan controller all together...

anyway, hope that helps someone out there some time...
--scott