On Tue, 2012-04-24 at 23:07 -0400, Brian J. Murrell wrote: > On 12-04-24 06:42 PM, Andy Walls wrote: > > Run 'femon' on the cx18's dvb frontend when you have a live QAM capture > > ongoing. > > OK. Ran it all evening during the evening capture window. Started it > at 20:30, sharp to coincide with the evening's recording from that card > also starting at 20:30 sharp. Here's where it found anomalies: > > $ nl /var/tmp/femon.out | grep -v "| ber 00000000 | unc 00000000 |" grepping out the 0 lines doesn't let one see the trends in Signal to Noise Ratio (SNR) before and after the uncorrectable (unc) block counts. > So you can see, since femon prints an output line each second, the > number on the left is the seconds since 20:30 and we are looking > for any line showing a ber or unc that is non-zero: Cool. First. note the following about the s5h1409 driver for the CX24227 (aka S5H109) QAM/8VSB demodulator: a. the Bit Eror Rate (BER) as returned by the driver is bogus; ignore it. It is just a copy of the uncorrectable block count. b. The "signal" level is a software computed value based on the SNR value. Ignore "signal" as redundant information. c. The Signal to Noise Ratio (SNR) should be a hexadecimal value with units of 1/10th of a deciBel (0.1 dB) (centiBels?). E.g. 0x13a => 314 => 31.4 dB I believe Steven calibrated this value to SNR at the RF input of the HVR-1600. (Steven or Devin, correct me if I am wrong.) > 1 FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC) > 67 status SCVYL | signal 013a | snr 013a | ber 00000198 | unc 00000198 | FE_HAS_LOCK > 313 status SCVYL | signal 013c | snr 013c | ber 0000026b | unc 0000026b | FE_HAS_LOCK > 457 status SCVYL | signal 013a | snr 013a | ber 0000026e | unc 0000026e | FE_HAS_LOCK > 802 status SCVYL | signal 013c | snr 013c | ber 00000265 | unc 00000265 | FE_HAS_LOCK > 1093 status SCVYL | signal 013a | snr 013a | ber 0000014b | unc 0000014b | FE_HAS_LOCK > 1184 status SCVYL | signal 013a | snr 013a | ber 000001ca | unc 000001ca | FE_HAS_LOCK > 1192 status SCVYL | signal 013a | snr 013a | ber 00000267 | unc 00000267 | FE_HAS_LOCK > 1385 status SCVYL | signal 013c | snr 013c | ber 0000025d | unc 0000025d | FE_HAS_LOCK > 1435 status SCVYL | signal 013c | snr 013c | ber 00000268 | unc 00000268 | FE_HAS_LOCK > 1511 status SCVYL | signal 013c | snr 013c | ber 0000026c | unc 0000026c | FE_HAS_LOCK > 1657 status SCVYL | signal 013a | snr 013a | ber 0000026a | unc 0000026a | FE_HAS_LOCK > 1693 status SCVYL | signal 013a | snr 013c | ber 0000026f | unc 0000026f | FE_HAS_LOCK > 1749 status SCVYL | signal 013c | snr 013c | ber 00000184 | unc 00000184 | FE_HAS_LOCK > 1796 status SCVYL | signal 013a | snr 013a | ber 00001a8b | unc 00001a8b | FE_HAS_LOCK > 1814 status SCVYL | signal 013c | snr 013c | ber 0000026d | unc 0000026d | FE_HAS_LOCK > 2028 status SCVYL | signal 013c | snr 013c | ber 00000275 | unc 00000275 | FE_HAS_LOCK > 2081 status SCVYL | signal 013c | snr 013c | ber 0000023a | unc 0000023a | FE_HAS_LOCK > 2261 status SCVYL | signal 013c | snr 013c | ber 00000264 | unc 00000264 | FE_HAS_LOCK > 2307 status SCVYL | signal 013c | snr 013c | ber 00000279 | unc 00000279 | FE_HAS_LOCK > 2318 status SCVYL | signal 013c | snr 013c | ber 0000026b | unc 0000026b | FE_HAS_LOCK > 2474 status SCVYL | signal 013a | snr 013a | ber 0000026f | unc 0000026f | FE_HAS_LOCK > 2533 status SCVYL | signal 013c | snr 013c | ber 00000098 | unc 00000098 | FE_HAS_LOCK > 2612 status SCVYL | signal 013a | snr 013a | ber 0000026a | unc 0000026a | FE_HAS_LOCK > 2627 status SCVYL | signal 013c | snr 013c | ber 00000108 | unc 00000108 | FE_HAS_LOCK > 2671 status SCVYL | signal 013c | snr 013c | ber 00000196 | unc 00000196 | FE_HAS_LOCK > 2870 status SCVYL | signal 013c | snr 013c | ber 00000264 | unc 00000264 | FE_HAS_LOCK > 3084 status SCVYL | signal 013c | snr 013c | ber 00000274 | unc 00000274 | FE_HAS_LOCK > 3220 status SCVYL | signal 013c | snr 013c | ber 00000275 | unc 00000275 | FE_HAS_LOCK > 3323 status SCVYL | signal 013c | snr 013c | ber 0000026b | unc 0000026b | FE_HAS_LOCK > 3406 status SCVYL | signal 013c | snr 013c | ber 0000024f | unc 0000024f | FE_HAS_LOCK > 3433 status SCVYL | signal 013c | snr 013a | ber 0000022a | unc 0000022a | FE_HAS_LOCK > 3946 status SCVYL | signal 013c | snr 013c | ber 00000270 | unc 00000270 | FE_HAS_LOCK > 4129 status SCVYL | signal 013c | snr 013c | ber 0000026d | unc 0000026d | FE_HAS_LOCK > 4275 status SCVYL | signal 013c | snr 013c | ber 00000273 | unc 00000273 | FE_HAS_LOCK > 4284 status SCVYL | signal 013c | snr 013c | ber 00000267 | unc 00000267 | FE_HAS_LOCK > 4411 status SCVYL | signal 013c | snr 013c | ber 00000270 | unc 00000270 | FE_HAS_LOCK > 4718 status SCVYL | signal 013c | snr 013c | ber 00000204 | unc 00000204 | FE_HAS_LOCK > 4779 status SCVYL | signal 013c | snr 013c | ber 00000181 | unc 00000181 | FE_HAS_LOCK > 4927 status SCVYL | signal 013c | snr 013c | ber 0000025e | unc 0000025e | FE_HAS_LOCK > 4973 status SCVYL | signal 013c | snr 013c | ber 00000157 | unc 00000157 | FE_HAS_LOCK > 5024 status SCVYL | signal 013c | snr 013c | ber 0000024c | unc 0000024c | FE_HAS_LOCK > 5310 status SCVYL | signal 013c | snr 013c | ber 00000190 | unc 00000190 | FE_HAS_LOCK > 5328 status SCVYL | signal 013c | snr 013c | ber 00000277 | unc 00000277 | FE_HAS_LOCK > 5439 status SCVYL | signal 013a | snr 013a | ber 0000026a | unc 0000026a | FE_HAS_LOCK > 5441 status SCVYL | signal 0138 | snr 0138 | ber 0000024f | unc 0000024f | FE_HAS_LOCK > 5447 status SCVYL | signal 0138 | snr 0138 | ber 00000266 | unc 00000266 | FE_HAS_LOCK > 5885 status SCVYL | signal 013a | snr 013a | ber 000000b3 | unc 000000b3 | FE_HAS_LOCK > 5928 status SCVYL | signal 013a | snr 013a | ber 0000020b | unc 0000020b | FE_HAS_LOCK > 5942 status SCVYL | signal 013a | snr 013a | ber 0000026b | unc 0000026b | FE_HAS_LOCK > 5966 status SCVYL | signal 013a | snr 013a | ber 000004d4 | unc 000004d4 | FE_HAS_LOCK > 6178 status SCVYL | signal 013a | snr 013a | ber 0000026c | unc 0000026c | FE_HAS_LOCK > 6657 status SCVYL | signal 0138 | snr 013a | ber 0000026e | unc 0000026e | FE_HAS_LOCK > 6761 status SCVYL | signal 013a | snr 013a | ber 00000268 | unc 00000268 | FE_HAS_LOCK > 6769 status SCVYL | signal 013a | snr 013a | ber 00000276 | unc 00000276 | FE_HAS_LOCK > 6777 status SCVYL | signal 013a | snr 013a | ber 00000277 | unc 00000277 | FE_HAS_LOCK > 6814 status SCVYL | signal 013a | snr 013a | ber 00000267 | unc 00000267 | FE_HAS_LOCK > 6868 status SCVYL | signal 0138 | snr 0138 | ber 00000171 | unc 00000171 | FE_HAS_LOCK > 6881 status SCVYL | signal 0138 | snr 0138 | ber 00000198 | unc 00000198 | FE_HAS_LOCK > 6891 status SCVYL | signal 0136 | snr 0138 | ber 00000249 | unc 00000249 | FE_HAS_LOCK > 6924 status SCVYL | signal 0138 | snr 0138 | ber 0000026b | unc 0000026b | FE_HAS_LOCK > 7116 status SCVYL | signal 0138 | snr 0138 | ber 00000150 | unc 00000150 | FE_HAS_LOCK > 7119 status SCVYL | signal 0138 | snr 0138 | ber 00000197 | unc 00000197 | FE_HAS_LOCK > 7140 status SCVYL | signal 0138 | snr 0138 | ber 00000270 | unc 00000270 | FE_HAS_LOCK > 7602 status SCVYL | signal 0138 | snr 0138 | ber 00000264 | unc 00000264 | FE_HAS_LOCK > 7716 status SCVYL | signal 0138 | snr 0138 | ber 00000194 | unc 00000194 | FE_HAS_LOCK > 7732 status SCVYL | signal 0138 | snr 0138 | ber 00000272 | unc 00000272 | FE_HAS_LOCK > 7751 status SCVYL | signal 013a | snr 0138 | ber 00000181 | unc 00000181 | FE_HAS_LOCK > 7770 status SCVYL | signal 013a | snr 013a | ber 00000270 | unc 00000270 | FE_HAS_LOCK > 7781 status SCVYL | signal 0138 | snr 0138 | ber 0000026f | unc 0000026f | FE_HAS_LOCK > 7796 status SCVYL | signal 0138 | snr 0138 | ber 00000275 | unc 00000275 | FE_HAS_LOCK > 7808 status SCVYL | signal 0138 | snr 0138 | ber 0000022f | unc 0000022f | FE_HAS_LOCK > 7816 status SCVYL | signal 013a | snr 0138 | ber 0000024e | unc 0000024e | FE_HAS_LOCK > 7822 status SCVYL | signal 013a | snr 013a | ber 00000270 | unc 00000270 | FE_HAS_LOCK > 7956 status SCVYL | signal 0138 | snr 0138 | ber 00000268 | unc 00000268 | FE_HAS_LOCK > 8008 status SCVYL | signal 0138 | snr 0138 | ber 0000026d | unc 0000026d | FE_HAS_LOCK > 8011 status SCVYL | signal 0138 | snr 0138 | ber 00000260 | unc 00000260 | FE_HAS_LOCK > 8232 status SCVYL | signal 013a | snr 013a | ber 0000024b | unc 0000024b | FE_HAS_LOCK > 8235 status SCVYL | signal 013a | snr 013a | ber 00000073 | unc 00000073 | FE_HAS_LOCK > 8255 status SCVYL | signal 0138 | snr 0138 | ber 00000254 | unc 00000254 | FE_HAS_LOCK > 8274 status SCVYL | signal 0138 | snr 0138 | ber 0000024e | unc 0000024e | FE_HAS_LOCK > 8303 status SCVYL | signal 0138 | snr 0138 | ber 0000017f | unc 0000017f | FE_HAS_LOCK > 8305 status SCVYL | signal 0138 | snr 0138 | ber 00000184 | unc 00000184 | FE_HAS_LOCK > 8354 status SCVYL | signal 013a | snr 0138 | ber 00000270 | unc 00000270 | FE_HAS_LOCK > 8442 status SCVYL | signal 0138 | snr 0138 | ber 0000024b | unc 0000024b | FE_HAS_LOCK > 8473 status SCVYL | signal 0138 | snr 0138 | ber 0000014b | unc 0000014b | FE_HAS_LOCK > 8510 status SCVYL | signal 0138 | snr 0138 | ber 00000253 | unc 00000253 | FE_HAS_LOCK > 8557 status SCVYL | signal 013a | snr 013a | ber 00000260 | unc 00000260 | FE_HAS_LOCK > 8578 status SCVYL | signal 013a | snr 013a | ber 00000259 | unc 00000259 | FE_HAS_LOCK > 8639 status SCVYL | signal 0138 | snr 0138 | ber 00000151 | unc 00000151 | FE_HAS_LOCK > 8742 status SCVYL | signal 013a | snr 0138 | ber 0000018c | unc 0000018c | FE_HAS_LOCK > 8820 status SCVYL | signal 0138 | snr 0138 | ber 00000265 | unc 00000265 | FE_HAS_LOCK So I see SNR values from 0x138 to 0x13c ( 31.2 dB to 31.6 dB ) when you have problems. For 256-QAM cable signals, I think that is considered marginal. (Can someone else with 256-QAM North American cable please confirm? I only have OTA) When you have no errors, what is the SNR? I'm guessing there are no large swings. > First recording of the evening shows "glitches" at the following > intervals: > > 4 > 130 > 157 > 396 > 742 > 790 > 1035 > 1035 > 1035 > 1071 > 1134 > 1146 > 1203 > 1256 > 1328 > 1338 > 1378 > 1602 > 1638 > 1694 > > Not sure if that's a close enough correlation or not. Hard to tell, given that one of the other digital sub-channels may have been effected and not visible on the channel you were recording. I normally watch DTV live with mplayer, and also have femon open in another window, when performing this sort of test. A video or audio glitch, 1 or 2 seconds after a non-zero uncorrectable block count, is usually a good indicator of correlation. > Not even sure > what those ber and unc values even mean. > > > Watch for the BER or UNCorrectable block count to increase at about the > > same time you view a glitch in the video. If this is the case, there is > > something about the signal the HVR-1600 is having trouble with. (The > > older models don't have the best digital tuner and digital demod > > combination out there.) > > So just sucky hardware in general? Well, not the best performer from what I hear. But certainly works just fine for many people in many contexts. > > If the signal shown in femon is at a relatively high level most of the > > time, then the cable signal probably has an instantaneous signal that > > sometimes overdrives the frontend. An inline attenuator might make the > > problem go away. > > If the signal is at a low level, it may drop below threshold > > occasionally. An in line amplifier, installed as close to where the > > signal comes into you home as possible, might help. > > Not sure if those signal and snr values represent normal, low or high > levels. The values displayed above are fairly representative of the > rest of the samples for the period in terms of signal and snr. OK. There are two ways to go here: 1. We assume your signal is marginal. Take a look here for things to check and fix if needed: http://ivtvdriver.org/index.php/Howto:Improve_signal_quality As a test, you you might also want to temporarily change your coax wiring setup to reduce the number of splits and connectors before the signal goes into the HVR-1600, and see if things are better. Every 2-way splitter will drop 3-5 dB of signal. 2. We assume your signal is too strong, and that it is overdriving the MXL5005s digital tuner of the HVR-1600, causing problems for the CX24227 demodulator. Your corrective action here would be to attenuate the incoming RF signal with either an inline attenuator, or with additional, properly terminated, splitters. An in line attenuator is pretty cheap (~US$2) from on-line sources: http://www.google.com/search?hl=en&tbm=shop&q=75+ohm+in+line+attenuator If you have some resistors lying around, you can make your own bridged-T inline attenuator for testing purposes: http://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg08735.html Regards, Andy -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
